KUnit tests are not supposed to run on production systems: they may do deliberately illegal things to trigger errors, and have security implications (assertions will often deliberately leak kernel addresses).
Add a new taint type, TAINT_KUNIT to signal that a KUnit test has been run. This will be printed as 'N' (for kuNit, as K, U and T were already taken).
This should discourage people from running KUnit tests on production systems, and to make it easier to tell if tests have been run accidentally (by loading the wrong configuration, etc.)
Signed-off-by: David Gow davidgow@google.com ---
This is something I'd been thinking about for a while, and it came up again, so I'm finally giving it a go.
Two notes: - I decided to add a new type of taint, as none of the existing ones really seemed to fit. We could live with considering KUnit tests as TAINT_WARN or TAINT_CRAP or something otherwise, but neither are quite right. - The taint_flags table gives a couple of checkpatch.pl errors around bracket placement. I've kept the new entry consistent with what's there rather than reformatting the whole table, but be prepared for complaints about spaces.
Thoughts? -- David
--- Documentation/admin-guide/tainted-kernels.rst | 1 + include/linux/panic.h | 3 ++- kernel/panic.c | 1 + lib/kunit/test.c | 4 ++++ 4 files changed, 8 insertions(+), 1 deletion(-)
diff --git a/Documentation/admin-guide/tainted-kernels.rst b/Documentation/admin-guide/tainted-kernels.rst index ceeed7b0798d..8f18fc4659d4 100644 --- a/Documentation/admin-guide/tainted-kernels.rst +++ b/Documentation/admin-guide/tainted-kernels.rst @@ -100,6 +100,7 @@ Bit Log Number Reason that got the kernel tainted 15 _/K 32768 kernel has been live patched 16 _/X 65536 auxiliary taint, defined for and used by distros 17 _/T 131072 kernel was built with the struct randomization plugin + 18 _/N 262144 a KUnit test has been run === === ====== ========================================================
Note: The character ``_`` is representing a blank in this table to make reading diff --git a/include/linux/panic.h b/include/linux/panic.h index f5844908a089..1d316c26bf27 100644 --- a/include/linux/panic.h +++ b/include/linux/panic.h @@ -74,7 +74,8 @@ static inline void set_arch_panic_timeout(int timeout, int arch_default_timeout) #define TAINT_LIVEPATCH 15 #define TAINT_AUX 16 #define TAINT_RANDSTRUCT 17 -#define TAINT_FLAGS_COUNT 18 +#define TAINT_KUNIT 18 +#define TAINT_FLAGS_COUNT 19 #define TAINT_FLAGS_MAX ((1UL << TAINT_FLAGS_COUNT) - 1)
struct taint_flag { diff --git a/kernel/panic.c b/kernel/panic.c index eb4dfb932c85..b24ca63ed738 100644 --- a/kernel/panic.c +++ b/kernel/panic.c @@ -404,6 +404,7 @@ const struct taint_flag taint_flags[TAINT_FLAGS_COUNT] = { [ TAINT_LIVEPATCH ] = { 'K', ' ', true }, [ TAINT_AUX ] = { 'X', ' ', true }, [ TAINT_RANDSTRUCT ] = { 'T', ' ', true }, + [ TAINT_KUNIT ] = { 'N', ' ', false }, };
/** diff --git a/lib/kunit/test.c b/lib/kunit/test.c index 0f66c13d126e..ea8e9162445d 100644 --- a/lib/kunit/test.c +++ b/lib/kunit/test.c @@ -11,6 +11,7 @@ #include <kunit/test-bug.h> #include <linux/kernel.h> #include <linux/moduleparam.h> +#include <linux/panic.h> #include <linux/sched/debug.h> #include <linux/sched.h>
@@ -498,6 +499,9 @@ int kunit_run_tests(struct kunit_suite *suite) struct kunit_result_stats suite_stats = { 0 }; struct kunit_result_stats total_stats = { 0 };
+ /* Taint the kernel so we know we've run tests. */ + add_taint(TAINT_KUNIT, LOCKDEP_STILL_OK); + kunit_print_subtest_start(suite);
kunit_suite_for_each_test_case(suite, test_case) {
On Fri, Apr 29, 2022 at 12:39:14PM +0800, David Gow wrote:
KUnit tests are not supposed to run on production systems: they may do deliberately illegal things to trigger errors, and have security implications (assertions will often deliberately leak kernel addresses).
Add a new taint type, TAINT_KUNIT to signal that a KUnit test has been run. This will be printed as 'N' (for kuNit, as K, U and T were already taken).
This should discourage people from running KUnit tests on production systems, and to make it easier to tell if tests have been run accidentally (by loading the wrong configuration, etc.)
Signed-off-by: David Gow davidgow@google.com
This is something I'd been thinking about for a while, and it came up again, so I'm finally giving it a go.
Two notes:
- I decided to add a new type of taint, as none of the existing ones really seemed to fit. We could live with considering KUnit tests as TAINT_WARN or TAINT_CRAP or something otherwise, but neither are quite right.
- The taint_flags table gives a couple of checkpatch.pl errors around bracket placement. I've kept the new entry consistent with what's there rather than reformatting the whole table, but be prepared for complaints about spaces.
Thoughts? -- David
Documentation/admin-guide/tainted-kernels.rst | 1 + include/linux/panic.h | 3 ++- kernel/panic.c | 1 + lib/kunit/test.c | 4 ++++ 4 files changed, 8 insertions(+), 1 deletion(-)
diff --git a/Documentation/admin-guide/tainted-kernels.rst b/Documentation/admin-guide/tainted-kernels.rst index ceeed7b0798d..8f18fc4659d4 100644 --- a/Documentation/admin-guide/tainted-kernels.rst +++ b/Documentation/admin-guide/tainted-kernels.rst @@ -100,6 +100,7 @@ Bit Log Number Reason that got the kernel tainted 15 _/K 32768 kernel has been live patched 16 _/X 65536 auxiliary taint, defined for and used by distros 17 _/T 131072 kernel was built with the struct randomization plugin
- 18 _/N 262144 a KUnit test has been run
=== === ====== ======================================================== Note: The character ``_`` is representing a blank in this table to make reading diff --git a/include/linux/panic.h b/include/linux/panic.h index f5844908a089..1d316c26bf27 100644 --- a/include/linux/panic.h +++ b/include/linux/panic.h @@ -74,7 +74,8 @@ static inline void set_arch_panic_timeout(int timeout, int arch_default_timeout) #define TAINT_LIVEPATCH 15 #define TAINT_AUX 16 #define TAINT_RANDSTRUCT 17 -#define TAINT_FLAGS_COUNT 18 +#define TAINT_KUNIT 18 +#define TAINT_FLAGS_COUNT 19 #define TAINT_FLAGS_MAX ((1UL << TAINT_FLAGS_COUNT) - 1) struct taint_flag { diff --git a/kernel/panic.c b/kernel/panic.c index eb4dfb932c85..b24ca63ed738 100644 --- a/kernel/panic.c +++ b/kernel/panic.c @@ -404,6 +404,7 @@ const struct taint_flag taint_flags[TAINT_FLAGS_COUNT] = { [ TAINT_LIVEPATCH ] = { 'K', ' ', true }, [ TAINT_AUX ] = { 'X', ' ', true }, [ TAINT_RANDSTRUCT ] = { 'T', ' ', true },
- [ TAINT_KUNIT ] = { 'N', ' ', false },
As kunit tests can be in modules, shouldn't this be "true" here?
Overall, I like it, makes sense to me. The "N" will take some getting used to, and I have no idea why "T" was for "struct randomization", that would have allowed you to use "T" instead. Oh well.
thanks,
greg k-h
On Fri, 29 Apr 2022, Greg KH gregkh@linuxfoundation.org wrote:
On Fri, Apr 29, 2022 at 12:39:14PM +0800, David Gow wrote:
KUnit tests are not supposed to run on production systems: they may do deliberately illegal things to trigger errors, and have security implications (assertions will often deliberately leak kernel addresses).
Add a new taint type, TAINT_KUNIT to signal that a KUnit test has been run. This will be printed as 'N' (for kuNit, as K, U and T were already taken).
This should discourage people from running KUnit tests on production systems, and to make it easier to tell if tests have been run accidentally (by loading the wrong configuration, etc.)
Signed-off-by: David Gow davidgow@google.com
This is something I'd been thinking about for a while, and it came up again, so I'm finally giving it a go.
Two notes:
- I decided to add a new type of taint, as none of the existing ones really seemed to fit. We could live with considering KUnit tests as TAINT_WARN or TAINT_CRAP or something otherwise, but neither are quite right.
- The taint_flags table gives a couple of checkpatch.pl errors around bracket placement. I've kept the new entry consistent with what's there rather than reformatting the whole table, but be prepared for complaints about spaces.
Thoughts? -- David
Documentation/admin-guide/tainted-kernels.rst | 1 + include/linux/panic.h | 3 ++- kernel/panic.c | 1 + lib/kunit/test.c | 4 ++++ 4 files changed, 8 insertions(+), 1 deletion(-)
diff --git a/Documentation/admin-guide/tainted-kernels.rst b/Documentation/admin-guide/tainted-kernels.rst index ceeed7b0798d..8f18fc4659d4 100644 --- a/Documentation/admin-guide/tainted-kernels.rst +++ b/Documentation/admin-guide/tainted-kernels.rst @@ -100,6 +100,7 @@ Bit Log Number Reason that got the kernel tainted 15 _/K 32768 kernel has been live patched 16 _/X 65536 auxiliary taint, defined for and used by distros 17 _/T 131072 kernel was built with the struct randomization plugin
- 18 _/N 262144 a KUnit test has been run
=== === ====== ======================================================== Note: The character ``_`` is representing a blank in this table to make reading diff --git a/include/linux/panic.h b/include/linux/panic.h index f5844908a089..1d316c26bf27 100644 --- a/include/linux/panic.h +++ b/include/linux/panic.h @@ -74,7 +74,8 @@ static inline void set_arch_panic_timeout(int timeout, int arch_default_timeout) #define TAINT_LIVEPATCH 15 #define TAINT_AUX 16 #define TAINT_RANDSTRUCT 17 -#define TAINT_FLAGS_COUNT 18 +#define TAINT_KUNIT 18 +#define TAINT_FLAGS_COUNT 19 #define TAINT_FLAGS_MAX ((1UL << TAINT_FLAGS_COUNT) - 1) struct taint_flag { diff --git a/kernel/panic.c b/kernel/panic.c index eb4dfb932c85..b24ca63ed738 100644 --- a/kernel/panic.c +++ b/kernel/panic.c @@ -404,6 +404,7 @@ const struct taint_flag taint_flags[TAINT_FLAGS_COUNT] = { [ TAINT_LIVEPATCH ] = { 'K', ' ', true }, [ TAINT_AUX ] = { 'X', ' ', true }, [ TAINT_RANDSTRUCT ] = { 'T', ' ', true },
- [ TAINT_KUNIT ] = { 'N', ' ', false },
As kunit tests can be in modules, shouldn't this be "true" here?
Overall, I like it, makes sense to me. The "N" will take some getting used to, and I have no idea why "T" was for "struct randomization", that would have allowed you to use "T" instead. Oh well.
Would you consider a patch adding more self-explanatory taint flag strings to the output?
BR, Jani.
On Fri, Apr 29, 2022 at 02:21:26PM +0300, Jani Nikula wrote:
On Fri, 29 Apr 2022, Greg KH gregkh@linuxfoundation.org wrote:
On Fri, Apr 29, 2022 at 12:39:14PM +0800, David Gow wrote:
KUnit tests are not supposed to run on production systems: they may do deliberately illegal things to trigger errors, and have security implications (assertions will often deliberately leak kernel addresses).
Add a new taint type, TAINT_KUNIT to signal that a KUnit test has been run. This will be printed as 'N' (for kuNit, as K, U and T were already taken).
This should discourage people from running KUnit tests on production systems, and to make it easier to tell if tests have been run accidentally (by loading the wrong configuration, etc.)
Signed-off-by: David Gow davidgow@google.com
This is something I'd been thinking about for a while, and it came up again, so I'm finally giving it a go.
Two notes:
- I decided to add a new type of taint, as none of the existing ones really seemed to fit. We could live with considering KUnit tests as TAINT_WARN or TAINT_CRAP or something otherwise, but neither are quite right.
- The taint_flags table gives a couple of checkpatch.pl errors around bracket placement. I've kept the new entry consistent with what's there rather than reformatting the whole table, but be prepared for complaints about spaces.
Thoughts? -- David
Documentation/admin-guide/tainted-kernels.rst | 1 + include/linux/panic.h | 3 ++- kernel/panic.c | 1 + lib/kunit/test.c | 4 ++++ 4 files changed, 8 insertions(+), 1 deletion(-)
diff --git a/Documentation/admin-guide/tainted-kernels.rst b/Documentation/admin-guide/tainted-kernels.rst index ceeed7b0798d..8f18fc4659d4 100644 --- a/Documentation/admin-guide/tainted-kernels.rst +++ b/Documentation/admin-guide/tainted-kernels.rst @@ -100,6 +100,7 @@ Bit Log Number Reason that got the kernel tainted 15 _/K 32768 kernel has been live patched 16 _/X 65536 auxiliary taint, defined for and used by distros 17 _/T 131072 kernel was built with the struct randomization plugin
- 18 _/N 262144 a KUnit test has been run
=== === ====== ======================================================== Note: The character ``_`` is representing a blank in this table to make reading diff --git a/include/linux/panic.h b/include/linux/panic.h index f5844908a089..1d316c26bf27 100644 --- a/include/linux/panic.h +++ b/include/linux/panic.h @@ -74,7 +74,8 @@ static inline void set_arch_panic_timeout(int timeout, int arch_default_timeout) #define TAINT_LIVEPATCH 15 #define TAINT_AUX 16 #define TAINT_RANDSTRUCT 17 -#define TAINT_FLAGS_COUNT 18 +#define TAINT_KUNIT 18 +#define TAINT_FLAGS_COUNT 19 #define TAINT_FLAGS_MAX ((1UL << TAINT_FLAGS_COUNT) - 1) struct taint_flag { diff --git a/kernel/panic.c b/kernel/panic.c index eb4dfb932c85..b24ca63ed738 100644 --- a/kernel/panic.c +++ b/kernel/panic.c @@ -404,6 +404,7 @@ const struct taint_flag taint_flags[TAINT_FLAGS_COUNT] = { [ TAINT_LIVEPATCH ] = { 'K', ' ', true }, [ TAINT_AUX ] = { 'X', ' ', true }, [ TAINT_RANDSTRUCT ] = { 'T', ' ', true },
- [ TAINT_KUNIT ] = { 'N', ' ', false },
As kunit tests can be in modules, shouldn't this be "true" here?
Overall, I like it, makes sense to me. The "N" will take some getting used to, and I have no idea why "T" was for "struct randomization", that would have allowed you to use "T" instead. Oh well.
Would you consider a patch adding more self-explanatory taint flag strings to the output?
Where would those strings go? In the oops report? Or somewhere else?
thanks,
greg k-h
On Fri, 29 Apr 2022, Greg KH gregkh@linuxfoundation.org wrote:
On Fri, Apr 29, 2022 at 02:21:26PM +0300, Jani Nikula wrote:
On Fri, 29 Apr 2022, Greg KH gregkh@linuxfoundation.org wrote:
On Fri, Apr 29, 2022 at 12:39:14PM +0800, David Gow wrote:
KUnit tests are not supposed to run on production systems: they may do deliberately illegal things to trigger errors, and have security implications (assertions will often deliberately leak kernel addresses).
Add a new taint type, TAINT_KUNIT to signal that a KUnit test has been run. This will be printed as 'N' (for kuNit, as K, U and T were already taken).
This should discourage people from running KUnit tests on production systems, and to make it easier to tell if tests have been run accidentally (by loading the wrong configuration, etc.)
Signed-off-by: David Gow davidgow@google.com
This is something I'd been thinking about for a while, and it came up again, so I'm finally giving it a go.
Two notes:
- I decided to add a new type of taint, as none of the existing ones really seemed to fit. We could live with considering KUnit tests as TAINT_WARN or TAINT_CRAP or something otherwise, but neither are quite right.
- The taint_flags table gives a couple of checkpatch.pl errors around bracket placement. I've kept the new entry consistent with what's there rather than reformatting the whole table, but be prepared for complaints about spaces.
Thoughts? -- David
Documentation/admin-guide/tainted-kernels.rst | 1 + include/linux/panic.h | 3 ++- kernel/panic.c | 1 + lib/kunit/test.c | 4 ++++ 4 files changed, 8 insertions(+), 1 deletion(-)
diff --git a/Documentation/admin-guide/tainted-kernels.rst b/Documentation/admin-guide/tainted-kernels.rst index ceeed7b0798d..8f18fc4659d4 100644 --- a/Documentation/admin-guide/tainted-kernels.rst +++ b/Documentation/admin-guide/tainted-kernels.rst @@ -100,6 +100,7 @@ Bit Log Number Reason that got the kernel tainted 15 _/K 32768 kernel has been live patched 16 _/X 65536 auxiliary taint, defined for and used by distros 17 _/T 131072 kernel was built with the struct randomization plugin
- 18 _/N 262144 a KUnit test has been run
=== === ====== ======================================================== Note: The character ``_`` is representing a blank in this table to make reading diff --git a/include/linux/panic.h b/include/linux/panic.h index f5844908a089..1d316c26bf27 100644 --- a/include/linux/panic.h +++ b/include/linux/panic.h @@ -74,7 +74,8 @@ static inline void set_arch_panic_timeout(int timeout, int arch_default_timeout) #define TAINT_LIVEPATCH 15 #define TAINT_AUX 16 #define TAINT_RANDSTRUCT 17 -#define TAINT_FLAGS_COUNT 18 +#define TAINT_KUNIT 18 +#define TAINT_FLAGS_COUNT 19 #define TAINT_FLAGS_MAX ((1UL << TAINT_FLAGS_COUNT) - 1) struct taint_flag { diff --git a/kernel/panic.c b/kernel/panic.c index eb4dfb932c85..b24ca63ed738 100644 --- a/kernel/panic.c +++ b/kernel/panic.c @@ -404,6 +404,7 @@ const struct taint_flag taint_flags[TAINT_FLAGS_COUNT] = { [ TAINT_LIVEPATCH ] = { 'K', ' ', true }, [ TAINT_AUX ] = { 'X', ' ', true }, [ TAINT_RANDSTRUCT ] = { 'T', ' ', true },
- [ TAINT_KUNIT ] = { 'N', ' ', false },
As kunit tests can be in modules, shouldn't this be "true" here?
Overall, I like it, makes sense to me. The "N" will take some getting used to, and I have no idea why "T" was for "struct randomization", that would have allowed you to use "T" instead. Oh well.
Would you consider a patch adding more self-explanatory taint flag strings to the output?
Where would those strings go? In the oops report? Or somewhere else?
I was thinking the oops report. Basically most times I look at an oops with taint, I need to double check what the flags mean. There are soon 19 of them, you need to look at a lot of oops to remember them all.
Currently we also print ' ' (or 'G' in case of non-properietary module) for every unset taint flag. If we stopped doing that we wouldn't even need that much more horizontal space for the strings, unless several flags were set. (I assume people who do remember all the flags by heart would still want to keep them too.)
BR, Jani.
thanks,
greg k-h
On Fri, Apr 29, 2022 at 02:54:25PM +0300, Jani Nikula wrote:
On Fri, 29 Apr 2022, Greg KH gregkh@linuxfoundation.org wrote:
On Fri, Apr 29, 2022 at 02:21:26PM +0300, Jani Nikula wrote:
On Fri, 29 Apr 2022, Greg KH gregkh@linuxfoundation.org wrote:
On Fri, Apr 29, 2022 at 12:39:14PM +0800, David Gow wrote:
KUnit tests are not supposed to run on production systems: they may do deliberately illegal things to trigger errors, and have security implications (assertions will often deliberately leak kernel addresses).
Add a new taint type, TAINT_KUNIT to signal that a KUnit test has been run. This will be printed as 'N' (for kuNit, as K, U and T were already taken).
This should discourage people from running KUnit tests on production systems, and to make it easier to tell if tests have been run accidentally (by loading the wrong configuration, etc.)
Signed-off-by: David Gow davidgow@google.com
This is something I'd been thinking about for a while, and it came up again, so I'm finally giving it a go.
Two notes:
- I decided to add a new type of taint, as none of the existing ones really seemed to fit. We could live with considering KUnit tests as TAINT_WARN or TAINT_CRAP or something otherwise, but neither are quite right.
- The taint_flags table gives a couple of checkpatch.pl errors around bracket placement. I've kept the new entry consistent with what's there rather than reformatting the whole table, but be prepared for complaints about spaces.
Thoughts? -- David
Documentation/admin-guide/tainted-kernels.rst | 1 + include/linux/panic.h | 3 ++- kernel/panic.c | 1 + lib/kunit/test.c | 4 ++++ 4 files changed, 8 insertions(+), 1 deletion(-)
diff --git a/Documentation/admin-guide/tainted-kernels.rst b/Documentation/admin-guide/tainted-kernels.rst index ceeed7b0798d..8f18fc4659d4 100644 --- a/Documentation/admin-guide/tainted-kernels.rst +++ b/Documentation/admin-guide/tainted-kernels.rst @@ -100,6 +100,7 @@ Bit Log Number Reason that got the kernel tainted 15 _/K 32768 kernel has been live patched 16 _/X 65536 auxiliary taint, defined for and used by distros 17 _/T 131072 kernel was built with the struct randomization plugin
- 18 _/N 262144 a KUnit test has been run
=== === ====== ======================================================== Note: The character ``_`` is representing a blank in this table to make reading diff --git a/include/linux/panic.h b/include/linux/panic.h index f5844908a089..1d316c26bf27 100644 --- a/include/linux/panic.h +++ b/include/linux/panic.h @@ -74,7 +74,8 @@ static inline void set_arch_panic_timeout(int timeout, int arch_default_timeout) #define TAINT_LIVEPATCH 15 #define TAINT_AUX 16 #define TAINT_RANDSTRUCT 17 -#define TAINT_FLAGS_COUNT 18 +#define TAINT_KUNIT 18 +#define TAINT_FLAGS_COUNT 19 #define TAINT_FLAGS_MAX ((1UL << TAINT_FLAGS_COUNT) - 1) struct taint_flag { diff --git a/kernel/panic.c b/kernel/panic.c index eb4dfb932c85..b24ca63ed738 100644 --- a/kernel/panic.c +++ b/kernel/panic.c @@ -404,6 +404,7 @@ const struct taint_flag taint_flags[TAINT_FLAGS_COUNT] = { [ TAINT_LIVEPATCH ] = { 'K', ' ', true }, [ TAINT_AUX ] = { 'X', ' ', true }, [ TAINT_RANDSTRUCT ] = { 'T', ' ', true },
- [ TAINT_KUNIT ] = { 'N', ' ', false },
As kunit tests can be in modules, shouldn't this be "true" here?
Overall, I like it, makes sense to me. The "N" will take some getting used to, and I have no idea why "T" was for "struct randomization", that would have allowed you to use "T" instead. Oh well.
Would you consider a patch adding more self-explanatory taint flag strings to the output?
Where would those strings go? In the oops report? Or somewhere else?
I was thinking the oops report. Basically most times I look at an oops with taint, I need to double check what the flags mean. There are soon 19 of them, you need to look at a lot of oops to remember them all.
I agree, it isn't easy to remember.
Currently we also print ' ' (or 'G' in case of non-properietary module) for every unset taint flag. If we stopped doing that we wouldn't even need that much more horizontal space for the strings, unless several flags were set. (I assume people who do remember all the flags by heart would still want to keep them too.)
I recommend keeping the current layout, but maybe adding a new line that gives the "key" for what the current taint flags mean?
For example, the oops report here: https://lore.kernel.org/r/20220413033425.GM16799@magnolia Has the lines: kernel BUG at mm/filemap.c:1653! invalid opcode: 0000 [#1] PREEMPT SMP CPU: 0 PID: 1349866 Comm: 0:116 Tainted: G W 5.18.0-rc2-djwx #rc2 19cc48221d47ada6c8e5859639b6a0946c9a3777 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS ?-20171121_152543-x86-ol7-builder-01.us.oracle.com-4.el7.1 04/01/2014 Workqueue: xfs-conv/sda4 xfs_end_io [xfs] RIP: 0010:folio_end_writeback+0x79/0x80
Perhaps we add another line right before or after "Hardware name:" that lists the flags that are set at the moment and what they mean:
Taint flags: [G]=PROPRIETARY_MODULE, [W]=WARN
Or something like that (format was a first guess only).
Anyway, might be helpful?
thanks,
greg k-h
On Fri, Apr 29, 2022 at 3:09 PM Greg KH gregkh@linuxfoundation.org wrote:
On Fri, Apr 29, 2022 at 12:39:14PM +0800, David Gow wrote:
KUnit tests are not supposed to run on production systems: they may do deliberately illegal things to trigger errors, and have security implications (assertions will often deliberately leak kernel addresses).
Add a new taint type, TAINT_KUNIT to signal that a KUnit test has been run. This will be printed as 'N' (for kuNit, as K, U and T were already taken).
This should discourage people from running KUnit tests on production systems, and to make it easier to tell if tests have been run accidentally (by loading the wrong configuration, etc.)
Signed-off-by: David Gow davidgow@google.com
< snip >
[ TAINT_KUNIT ] = { 'N', ' ', false },As kunit tests can be in modules, shouldn't this be "true" here?
Ah, good catch. While I tend to use either built-in tests (or modules which are immediately unloaded), there are definitely some cases where the tests are part of long-lasting modules.
I'll send out v2 with that changed.
Overall, I like it, makes sense to me. The "N" will take some getting used to, and I have no idea why "T" was for "struct randomization", that would have allowed you to use "T" instead. Oh well.
Yeah, 'T' would've been nice, but I doubt it'd be worth trying to change it now. At least we haven't had to resort to emoji...
Adding an actual name as Jani suggested would be a good idea, IMHO, though obviously best done in a separate patch.
Cheers, -- David
KUnit tests are not supposed to run on production systems: they may do deliberately illegal things to trigger errors, and have security implications (assertions will often deliberately leak kernel addresses).
Add a new taint type, TAINT_KUNIT to signal that a KUnit test has been run. This will be printed as 'N' (for kuNit, as K, U and T were already taken).
This should discourage people from running KUnit tests on production systems, and to make it easier to tell if tests have been run accidentally (by loading the wrong configuration, etc.)
Signed-off-by: David Gow davidgow@google.com ---
Changes since v1: https://lore.kernel.org/linux-kselftest/20220429043913.626647-1-davidgow@goo... - Make the taint per-module, to handle the case when tests are in (longer lasting) modules. (Thanks Greg KH).
Note that this still has checkpatch.pl warnings around bracket placement, which are intentional as part of matching the surrounding code.
--- Documentation/admin-guide/tainted-kernels.rst | 1 + include/linux/panic.h | 3 ++- kernel/panic.c | 1 + lib/kunit/test.c | 4 ++++ 4 files changed, 8 insertions(+), 1 deletion(-)
diff --git a/Documentation/admin-guide/tainted-kernels.rst b/Documentation/admin-guide/tainted-kernels.rst index ceeed7b0798d..8f18fc4659d4 100644 --- a/Documentation/admin-guide/tainted-kernels.rst +++ b/Documentation/admin-guide/tainted-kernels.rst @@ -100,6 +100,7 @@ Bit Log Number Reason that got the kernel tainted 15 _/K 32768 kernel has been live patched 16 _/X 65536 auxiliary taint, defined for and used by distros 17 _/T 131072 kernel was built with the struct randomization plugin + 18 _/N 262144 a KUnit test has been run === === ====== ========================================================
Note: The character ``_`` is representing a blank in this table to make reading diff --git a/include/linux/panic.h b/include/linux/panic.h index f5844908a089..1d316c26bf27 100644 --- a/include/linux/panic.h +++ b/include/linux/panic.h @@ -74,7 +74,8 @@ static inline void set_arch_panic_timeout(int timeout, int arch_default_timeout) #define TAINT_LIVEPATCH 15 #define TAINT_AUX 16 #define TAINT_RANDSTRUCT 17 -#define TAINT_FLAGS_COUNT 18 +#define TAINT_KUNIT 18 +#define TAINT_FLAGS_COUNT 19 #define TAINT_FLAGS_MAX ((1UL << TAINT_FLAGS_COUNT) - 1)
struct taint_flag { diff --git a/kernel/panic.c b/kernel/panic.c index eb4dfb932c85..9a026d98a00c 100644 --- a/kernel/panic.c +++ b/kernel/panic.c @@ -404,6 +404,7 @@ const struct taint_flag taint_flags[TAINT_FLAGS_COUNT] = { [ TAINT_LIVEPATCH ] = { 'K', ' ', true }, [ TAINT_AUX ] = { 'X', ' ', true }, [ TAINT_RANDSTRUCT ] = { 'T', ' ', true }, + [ TAINT_KUNIT ] = { 'N', ' ', true }, };
/** diff --git a/lib/kunit/test.c b/lib/kunit/test.c index 0f66c13d126e..ea8e9162445d 100644 --- a/lib/kunit/test.c +++ b/lib/kunit/test.c @@ -11,6 +11,7 @@ #include <kunit/test-bug.h> #include <linux/kernel.h> #include <linux/moduleparam.h> +#include <linux/panic.h> #include <linux/sched/debug.h> #include <linux/sched.h>
@@ -498,6 +499,9 @@ int kunit_run_tests(struct kunit_suite *suite) struct kunit_result_stats suite_stats = { 0 }; struct kunit_result_stats total_stats = { 0 };
+ /* Taint the kernel so we know we've run tests. */ + add_taint(TAINT_KUNIT, LOCKDEP_STILL_OK); + kunit_print_subtest_start(suite);
kunit_suite_for_each_test_case(suite, test_case) {
On Sat, Apr 30, 2022 at 11:00:19AM +0800, David Gow wrote:
KUnit tests are not supposed to run on production systems: they may do deliberately illegal things to trigger errors, and have security implications (assertions will often deliberately leak kernel addresses).
Add a new taint type, TAINT_KUNIT to signal that a KUnit test has been run. This will be printed as 'N' (for kuNit, as K, U and T were already taken).
This should discourage people from running KUnit tests on production systems, and to make it easier to tell if tests have been run accidentally (by loading the wrong configuration, etc.)
Signed-off-by: David Gow davidgow@google.com
Reviewed-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
On Sat, Apr 30, 2022 at 11:00:19AM +0800, David Gow wrote:
KUnit tests are not supposed to run on production systems: they may do deliberately illegal things to trigger errors, and have security implications (assertions will often deliberately leak kernel addresses).
Add a new taint type, TAINT_KUNIT to signal that a KUnit test has been run. This will be printed as 'N' (for kuNit, as K, U and T were already taken).
This should discourage people from running KUnit tests on production systems, and to make it easier to tell if tests have been run accidentally (by loading the wrong configuration, etc.)
Signed-off-by: David Gow davidgow@google.com
There is no reason to distinguish kunit from selftests if the result is the same: really make the kernel try really insane stupid things which may crash it or put it into a bad state.
So no, this should be renamed to "TEST_BREAK" as I think outside of selftest and kunit we may grow the kernel to do stupid things outside of that domain and this gives us the flexilibilty to use that in other places as well.
It begs the question if we *should* allow userspace to volunterally say "hey, we are doing really insane things, brace yourself." Why ? Well because selftest has tons of modules. We either then define a macro that adds the taint for them and wrap the module declaration for it, or we expose a syctl to let userspace volunteer to opt-in to seggest we are about to try something stupid with the kernel including loading some dangeerous modules which may not have macros which taint the kernel. That would let selftest taint on *any* selftest. Because we can run all selftests or run one selftest.
Then, if such sysctl is exposed, maybe we should then also use this for example for blktests, fstests, fio tests, etc.
Luis
On Sun, May 01, 2022 at 11:22:38AM -0700, Luis Chamberlain wrote:
On Sat, Apr 30, 2022 at 11:00:19AM +0800, David Gow wrote:
KUnit tests are not supposed to run on production systems: they may do deliberately illegal things to trigger errors, and have security implications (assertions will often deliberately leak kernel addresses).
Add a new taint type, TAINT_KUNIT to signal that a KUnit test has been run. This will be printed as 'N' (for kuNit, as K, U and T were already taken).
This should discourage people from running KUnit tests on production systems, and to make it easier to tell if tests have been run accidentally (by loading the wrong configuration, etc.)
Signed-off-by: David Gow davidgow@google.com
There is no reason to distinguish kunit from selftests if the result is the same: really make the kernel try really insane stupid things which may crash it or put it into a bad state.
So no, this should be renamed to "TEST_BREAK" as I think outside of selftest and kunit we may grow the kernel to do stupid things outside of that domain and this gives us the flexilibilty to use that in other places as well.
It begs the question if we *should* allow userspace to volunterally say "hey, we are doing really insane things, brace yourself." Why ? Well because selftest has tons of modules. We either then define a macro that adds the taint for them and wrap the module declaration for it, or we expose a syctl to let userspace volunteer to opt-in to seggest we are about to try something stupid with the kernel including loading some dangeerous modules which may not have macros which taint the kernel. That would let selftest taint on *any* selftest. Because we can run all selftests or run one selftest.
Then, if such sysctl is exposed, maybe we should then also use this for example for blktests, fstests, fio tests, etc.
For got to expand to fsdevel and linux-block.
Luis
On Mon, May 2, 2022 at 2:24 AM Luis Chamberlain mcgrof@kernel.org wrote:
On Sun, May 01, 2022 at 11:22:38AM -0700, Luis Chamberlain wrote:
On Sat, Apr 30, 2022 at 11:00:19AM +0800, David Gow wrote:
KUnit tests are not supposed to run on production systems: they may do deliberately illegal things to trigger errors, and have security implications (assertions will often deliberately leak kernel addresses).
Add a new taint type, TAINT_KUNIT to signal that a KUnit test has been run. This will be printed as 'N' (for kuNit, as K, U and T were already taken).
This should discourage people from running KUnit tests on production systems, and to make it easier to tell if tests have been run accidentally (by loading the wrong configuration, etc.)
Signed-off-by: David Gow davidgow@google.com
There is no reason to distinguish kunit from selftests if the result is the same: really make the kernel try really insane stupid things which may crash it or put it into a bad state.
My initial thought is that KUnit is explicitly in-kernel testing, whereas kselftest is (at least somewhat) user-space based. My personal feeling is that "doing weird stuff from userspace" is fundamentally different from "doing weird stuff in the kernel". That being said, in practice many kselftest tests load modules which do strange things, and those could be in scope for something like that. I'd still err on the side of only having those tests (or specifically those modules) add the taint, rather than all selftests, but could be conveniced.
The other thing of note is that KUnit tests do often leak pointer addresses, which again is something that's a worry in the kernel, and harmless in userspace.
So no, this should be renamed to "TEST_BREAK" as I think outside of selftest and kunit we may grow the kernel to do stupid things outside of that domain and this gives us the flexilibilty to use that in other places as well.
It begs the question if we *should* allow userspace to volunterally say "hey, we are doing really insane things, brace yourself." Why ? Well because selftest has tons of modules. We either then define a macro that adds the taint for them and wrap the module declaration for it, or we expose a syctl to let userspace volunteer to opt-in to seggest we are about to try something stupid with the kernel including loading some dangeerous modules which may not have macros which taint the kernel. That would let selftest taint on *any* selftest. Because we can run all selftests or run one selftest.
Then, if such sysctl is exposed, maybe we should then also use this for example for blktests, fstests, fio tests, etc.
Is this what TAINT_USER is for?
I think (though haven't actually tried) writing to /proc/sys/kernel/tainted will add whatever taint flags are needed from userspace.
That being said, I'm not _against_ making this more general, or standardising on the existing TAINT_USER, or similar. Personally, though, I quite like having KUnit separate (but I am, admittedly, biased :-) ).
Cheers, -- David
On Tue, May 03, 2022 at 02:49:58PM +0800, David Gow wrote:
On Mon, May 2, 2022 at 2:24 AM Luis Chamberlain mcgrof@kernel.org wrote:
On Sun, May 01, 2022 at 11:22:38AM -0700, Luis Chamberlain wrote:
On Sat, Apr 30, 2022 at 11:00:19AM +0800, David Gow wrote:
KUnit tests are not supposed to run on production systems: they may do deliberately illegal things to trigger errors, and have security implications (assertions will often deliberately leak kernel addresses).
Add a new taint type, TAINT_KUNIT to signal that a KUnit test has been run. This will be printed as 'N' (for kuNit, as K, U and T were already taken).
This should discourage people from running KUnit tests on production systems, and to make it easier to tell if tests have been run accidentally (by loading the wrong configuration, etc.)
Signed-off-by: David Gow davidgow@google.com
There is no reason to distinguish kunit from selftests if the result is the same: really make the kernel try really insane stupid things which may crash it or put it into a bad state.
My initial thought is that KUnit is explicitly in-kernel testing, whereas kselftest is (at least somewhat) user-space based.
selftests has modules, although I am not sure if there are selftests which do not load modules. Shuah?
My personal feeling is that "doing weird stuff from userspace" is fundamentally different from "doing weird stuff in the kernel".
True.
That being said, in practice many kselftest tests load modules which do strange things, and those could be in scope for something like that. I'd still err on the side of only having those tests (or specifically those modules) add the taint, rather than all selftests, but could be conveniced.
Yeah I think now that this can easily be added by having a special new module info, MODULE_TAINTS(taint_flag). Then in check_modinfo() you'd get_modinfo(info, "taints") to then add_taint_module() if set.
We can ignore the userspace thing I mentioned earlier as I thought at first we could not add the taint to selftest modules easily but we can.
Luis
On Wed, May 4, 2022 at 9:51 AM Luis Chamberlain mcgrof@kernel.org wrote:
selftests has modules, although I am not sure if there are selftests which do not load modules. Shuah?
I'm not Shuah, but there are indeed selftests that don't load modules.
I went looking for an example and found tools/testing/selftests/bpf/test_doc_build.sh, which runs entirely in userspace (basically just `make docs`).
On Wed, May 04, 2022 at 11:25:14AM -0500, Daniel Latypov wrote:
On Wed, May 4, 2022 at 9:51 AM Luis Chamberlain mcgrof@kernel.org wrote:
selftests has modules, although I am not sure if there are selftests which do not load modules. Shuah?
I'm not Shuah, but there are indeed selftests that don't load modules.
I went looking for an example and found tools/testing/selftests/bpf/test_doc_build.sh, which runs entirely in userspace (basically just `make docs`).
OK so, we can just skip tainting considerations for selftests which don't use modules for now. There may be selftests which do wonky things in userspace but indeed I agree the userspace taint would be better for those but I don't think it may be worth bother worrying about those at this point in time.
But my point in that sharing a taint between kunit / selftests modules does make sense and is easily possible. The unfortunate aspect is just that selftests don't have a centralized runner, because I can just run tools/testing/selftests/sysctl/sysctl.sh for example and that's it. So I think we have no other option but to just add the module info manually for selftests at this time.
Luis
On Wed, May 4, 2022 at 1:46 PM Luis Chamberlain mcgrof@kernel.org wrote:
OK so, we can just skip tainting considerations for selftests which don't use modules for now. There may be selftests which do wonky things in userspace but indeed I agree the userspace taint would be better for those but I don't think it may be worth bother worrying about those at this point in time.
But my point in that sharing a taint between kunit / selftests modules does make sense and is easily possible. The unfortunate aspect is just
Yes, I 100% agree that we should share a taint for kernelspace testing from both kunit/kselftest. Someone running the system won't care what framework was used.
that selftests don't have a centralized runner, because I can just run tools/testing/selftests/sysctl/sysctl.sh for example and that's it. So I think we have no other option but to just add the module info manually for selftests at this time.
Somewhat tangential: there's a number of other test modules that aren't explicitly part of kselftest. Long-term, I think most of them should be converted to kselftest or kunit as appropriate, so they'll get taken care of eventually.
A number of these modules depend on CONFIG_DEBUG_KERNEL=y, but we can't pre-emptively set this new taint flag by checking for it as it's too widely used :\ E.g. the debian-based distro I'm using right now has it set $ grep 'CONFIG_DEBUG_KERNEL=y' /boot/config-$(uname -r) CONFIG_DEBUG_KERNEL=y
-Daniel
On Wed, May 04, 2022 at 02:19:59PM -0500, Daniel Latypov wrote:
On Wed, May 4, 2022 at 1:46 PM Luis Chamberlain mcgrof@kernel.org wrote:
OK so, we can just skip tainting considerations for selftests which don't use modules for now. There may be selftests which do wonky things in userspace but indeed I agree the userspace taint would be better for those but I don't think it may be worth bother worrying about those at this point in time.
But my point in that sharing a taint between kunit / selftests modules does make sense and is easily possible. The unfortunate aspect is just
Yes, I 100% agree that we should share a taint for kernelspace testing from both kunit/kselftest. Someone running the system won't care what framework was used.
OK do you mind doing the nasty work of manually adding the new MODULE_TAINT() to the selftests as part of your effort?
*Alternatively*, if we *moved* all sefltests modules to a new lib/debug/selftests/ directory or something like that then t would seem modpost *could* add the taint flag automagically for us without having to edit or require it on new drivers. We have similar type of taint for staging, see add_staging_flag().
I would *highly* prefer this approach, event though it is more work, because I think this is a step we should take anyway.
However, I just checked modules on lib/ and well, some of them are already in their own directory, like lib/math/test_div64.c. So not sure, maybe just move a few modules which are just in lib/*.c for now and then just sprinkle the MODULE_TAINT() to the others?
that selftests don't have a centralized runner, because I can just run tools/testing/selftests/sysctl/sysctl.sh for example and that's it. So I think we have no other option but to just add the module info manually for selftests at this time.
Somewhat tangential: there's a number of other test modules that aren't explicitly part of kselftest.
Oh interesting, like which one?
Long-term, I think most of them should be converted to kselftest or kunit as appropriate, so they'll get taken care of eventually.
Makes sense.
Luis
On Wed, May 04, 2022 at 02:12:30PM -0700, Luis Chamberlain wrote:
On Wed, May 04, 2022 at 02:19:59PM -0500, Daniel Latypov wrote:
On Wed, May 4, 2022 at 1:46 PM Luis Chamberlain mcgrof@kernel.org wrote:
OK so, we can just skip tainting considerations for selftests which don't use modules for now. There may be selftests which do wonky things in userspace but indeed I agree the userspace taint would be better for those but I don't think it may be worth bother worrying about those at this point in time.
But my point in that sharing a taint between kunit / selftests modules does make sense and is easily possible. The unfortunate aspect is just
Yes, I 100% agree that we should share a taint for kernelspace testing from both kunit/kselftest. Someone running the system won't care what framework was used.
OK do you mind doing the nasty work of manually adding the new MODULE_TAINT() to the selftests as part of your effort?
*Alternatively*, if we *moved* all sefltests modules to a new lib/debug/selftests/ directory or something like that then t would seem modpost *could* add the taint flag automagically for us without having to edit or require it on new drivers. We have similar type of taint for staging, see add_staging_flag().
I would *highly* prefer this approach, event though it is more work, because I think this is a step we should take anyway.
However, I just checked modules on lib/ and well, some of them are already in their own directory, like lib/math/test_div64.c. So not sure, maybe just move a few modules which are just in lib/*.c for now and then just sprinkle the MODULE_TAINT() to the others?
I *think* we could just pull this off with a much easier approach, simply looking for the substrings in the module name in modpost.c:
* "_test." || "-test." * ^"test_" || ^"test-"
An issue with this of course is a vendor $FOO with an out of tree test driver may end up with the taint. Perhaps we don't care.
That means moving selftests to its own directory is not needed at this point in time.
Luis
On Thu, May 5, 2022 at 1:57 PM Luis Chamberlain mcgrof@kernel.org wrote:
On Wed, May 04, 2022 at 02:12:30PM -0700, Luis Chamberlain wrote:
On Wed, May 04, 2022 at 02:19:59PM -0500, Daniel Latypov wrote:
On Wed, May 4, 2022 at 1:46 PM Luis Chamberlain mcgrof@kernel.org wrote:
OK so, we can just skip tainting considerations for selftests which don't use modules for now. There may be selftests which do wonky things in userspace but indeed I agree the userspace taint would be better for those but I don't think it may be worth bother worrying about those at this point in time.
But my point in that sharing a taint between kunit / selftests modules does make sense and is easily possible. The unfortunate aspect is just
Yes, I 100% agree that we should share a taint for kernelspace testing from both kunit/kselftest. Someone running the system won't care what framework was used.
OK do you mind doing the nasty work of manually adding the new MODULE_TAINT() to the selftests as part of your effort?
*Alternatively*, if we *moved* all sefltests modules to a new lib/debug/selftests/ directory or something like that then t would seem modpost *could* add the taint flag automagically for us without having to edit or require it on new drivers. We have similar type of taint for staging, see add_staging_flag().
I would *highly* prefer this approach, event though it is more work, because I think this is a step we should take anyway.
However, I just checked modules on lib/ and well, some of them are already in their own directory, like lib/math/test_div64.c. So not sure, maybe just move a few modules which are just in lib/*.c for now and then just sprinkle the MODULE_TAINT() to the others?
I *think* we could just pull this off with a much easier approach, simply looking for the substrings in the module name in modpost.c:
- "_test." || "-test."
- ^"test_" || ^"test-"
An issue with this of course is a vendor $FOO with an out of tree test driver may end up with the taint. Perhaps we don't care.
That means moving selftests to its own directory is not needed at this point in time.
I can't say I'm thrilled with the idea of just doing name comparisons, particularly since not all of them match this pattern, for example: bpf_testmod.ko. (Though, frankly, more of them do than I'd've guessed.)
Maybe adding a taint call to the selftest helper module framework in kselftest_module.h, though again, there are several tests which don't use it.
I _suspect_ we'd be able to hit most of them by tainting in frameworks like the above, and patch the remaining modules manually. There's also definitely a grey area with things like netdevsim, which are used a lot as helper modules by selftests, but may have other uses as well.
(The advantage of the KUnit tainting is that, due to KUnit's centralised executor, we can be sure all KUnit tests will correctly trigger the taint. But maybe it doesn't matter as much if one or two selftests miss out.)
-- David
On Fri, May 06, 2022 at 03:01:34PM +0800, David Gow wrote:
On Thu, May 5, 2022 at 1:57 PM Luis Chamberlain mcgrof@kernel.org wrote:
On Wed, May 04, 2022 at 02:12:30PM -0700, Luis Chamberlain wrote:
On Wed, May 04, 2022 at 02:19:59PM -0500, Daniel Latypov wrote:
On Wed, May 4, 2022 at 1:46 PM Luis Chamberlain mcgrof@kernel.org wrote:
OK so, we can just skip tainting considerations for selftests which don't use modules for now. There may be selftests which do wonky things in userspace but indeed I agree the userspace taint would be better for those but I don't think it may be worth bother worrying about those at this point in time.
But my point in that sharing a taint between kunit / selftests modules does make sense and is easily possible. The unfortunate aspect is just
Yes, I 100% agree that we should share a taint for kernelspace testing from both kunit/kselftest. Someone running the system won't care what framework was used.
OK do you mind doing the nasty work of manually adding the new MODULE_TAINT() to the selftests as part of your effort?
*Alternatively*, if we *moved* all sefltests modules to a new lib/debug/selftests/ directory or something like that then t would seem modpost *could* add the taint flag automagically for us without having to edit or require it on new drivers. We have similar type of taint for staging, see add_staging_flag().
I would *highly* prefer this approach, event though it is more work, because I think this is a step we should take anyway.
However, I just checked modules on lib/ and well, some of them are already in their own directory, like lib/math/test_div64.c. So not sure, maybe just move a few modules which are just in lib/*.c for now and then just sprinkle the MODULE_TAINT() to the others?
I *think* we could just pull this off with a much easier approach, simply looking for the substrings in the module name in modpost.c:
- "_test." || "-test."
- ^"test_" || ^"test-"
An issue with this of course is a vendor $FOO with an out of tree test driver may end up with the taint. Perhaps we don't care.
That means moving selftests to its own directory is not needed at this point in time.
I can't say I'm thrilled with the idea of just doing name comparisons, particularly since not all of them match this pattern, for example: bpf_testmod.ko. (Though, frankly, more of them do than I'd've guessed.)
Maybe adding a taint call to the selftest helper module framework in kselftest_module.h, though again, there are several tests which don't use it.
Right, I can't think of a generic way to peg this. I think long term we do stand to gain to move all selftests under a lib/debug/selftests/ or something like that, but for now what I suggested is the only thing I can come up with.
I _suspect_ we'd be able to hit most of them by tainting in frameworks like the above, and patch the remaining modules manually.
Works with me.
There's also definitely a grey area with things like netdevsim, which are used a lot as helper modules by selftests, but may have other uses as well.
They can peg the module if they want the taint.
(The advantage of the KUnit tainting is that, due to KUnit's centralised executor, we can be sure all KUnit tests will correctly trigger the taint. But maybe it doesn't matter as much if one or two selftests miss out.)
That is what I was thinking.
I'm convinced we *should* move selftests to a one directory. The amount of stuff in lib/ is getting out of hand.
Luis
Most in-kernel tests (such as KUnit tests) are not supposed to run on production systems: they may do deliberately illegal things to trigger errors, and have security implications (for example, KUnit assertions will often deliberately leak kernel addresses).
Add a new taint type, TAINT_TEST to signal that a test has been run. This will be printed as 'N' (originally for kuNit, as every other sensible letter was taken.)
This should discourage people from running these tests on production systems, and to make it easier to tell if tests have been run accidentally (by loading the wrong configuration, etc.)
Signed-off-by: David Gow davidgow@google.com ---
Updated this to handle the most common case of selftest modules, in addition to KUnit tests. There's room for other tests or test frameworks to use this as well, either with a call to add_taint() from within the kernel, or by writing to /proc/sys/kernel/tainted.
The 'N' character for the taint is even less useful now that it's no longer short for kuNit, but all the letters in TEST are taken. :-(
Changes since v2: https://lore.kernel.org/linux-kselftest/20220430030019.803481-1-davidgow@goo... - Rename TAINT_KUNIT -> TAINT_TEST. - Split into separate patches for adding the taint, and triggering it. - Taint on a kselftest_module being loaded (patch 3/3)
Changes since v1: https://lore.kernel.org/linux-kselftest/20220429043913.626647-1-davidgow@goo... - Make the taint per-module, to handle the case when tests are in (longer lasting) modules. (Thanks Greg KH).
Note that this still has checkpatch.pl warnings around bracket placement, which are intentional as part of matching the surrounding code.
--- Documentation/admin-guide/tainted-kernels.rst | 1 + include/linux/panic.h | 3 ++- kernel/panic.c | 1 + 3 files changed, 4 insertions(+), 1 deletion(-)
diff --git a/Documentation/admin-guide/tainted-kernels.rst b/Documentation/admin-guide/tainted-kernels.rst index ceeed7b0798d..546f3071940d 100644 --- a/Documentation/admin-guide/tainted-kernels.rst +++ b/Documentation/admin-guide/tainted-kernels.rst @@ -100,6 +100,7 @@ Bit Log Number Reason that got the kernel tainted 15 _/K 32768 kernel has been live patched 16 _/X 65536 auxiliary taint, defined for and used by distros 17 _/T 131072 kernel was built with the struct randomization plugin + 18 _/N 262144 an in-kernel test (such as a KUnit test) has been run === === ====== ========================================================
Note: The character ``_`` is representing a blank in this table to make reading diff --git a/include/linux/panic.h b/include/linux/panic.h index f5844908a089..2f5f2a9ecaf7 100644 --- a/include/linux/panic.h +++ b/include/linux/panic.h @@ -74,7 +74,8 @@ static inline void set_arch_panic_timeout(int timeout, int arch_default_timeout) #define TAINT_LIVEPATCH 15 #define TAINT_AUX 16 #define TAINT_RANDSTRUCT 17 -#define TAINT_FLAGS_COUNT 18 +#define TAINT_TEST 18 +#define TAINT_FLAGS_COUNT 19 #define TAINT_FLAGS_MAX ((1UL << TAINT_FLAGS_COUNT) - 1)
struct taint_flag { diff --git a/kernel/panic.c b/kernel/panic.c index eb4dfb932c85..1cf707e3bacd 100644 --- a/kernel/panic.c +++ b/kernel/panic.c @@ -404,6 +404,7 @@ const struct taint_flag taint_flags[TAINT_FLAGS_COUNT] = { [ TAINT_LIVEPATCH ] = { 'K', ' ', true }, [ TAINT_AUX ] = { 'X', ' ', true }, [ TAINT_RANDSTRUCT ] = { 'T', ' ', true }, + [ TAINT_TEST ] = { 'N', ' ', true }, };
/**
On Fri, May 13, 2022 at 04:32:11PM +0800, David Gow wrote:
Most in-kernel tests (such as KUnit tests) are not supposed to run on production systems: they may do deliberately illegal things to trigger errors, and have security implications (for example, KUnit assertions will often deliberately leak kernel addresses).
Add a new taint type, TAINT_TEST to signal that a test has been run. This will be printed as 'N' (originally for kuNit, as every other sensible letter was taken.)
This should discourage people from running these tests on production systems, and to make it easier to tell if tests have been run accidentally (by loading the wrong configuration, etc.)
Signed-off-by: David Gow davidgow@google.com
Updated this to handle the most common case of selftest modules, in addition to KUnit tests. There's room for other tests or test frameworks to use this as well, either with a call to add_taint() from within the kernel, or by writing to /proc/sys/kernel/tainted.
The 'N' character for the taint is even less useful now that it's no longer short for kuNit, but all the letters in TEST are taken. :-(
Changes since v2: https://lore.kernel.org/linux-kselftest/20220430030019.803481-1-davidgow@goo...
- Rename TAINT_KUNIT -> TAINT_TEST.
- Split into separate patches for adding the taint, and triggering it.
- Taint on a kselftest_module being loaded (patch 3/3)
Changes since v1: https://lore.kernel.org/linux-kselftest/20220429043913.626647-1-davidgow@goo...
- Make the taint per-module, to handle the case when tests are in (longer lasting) modules. (Thanks Greg KH).
Note that this still has checkpatch.pl warnings around bracket placement, which are intentional as part of matching the surrounding code.
Documentation/admin-guide/tainted-kernels.rst | 1 + include/linux/panic.h | 3 ++- kernel/panic.c | 1 + 3 files changed, 4 insertions(+), 1 deletion(-)
diff --git a/Documentation/admin-guide/tainted-kernels.rst b/Documentation/admin-guide/tainted-kernels.rst index ceeed7b0798d..546f3071940d 100644 --- a/Documentation/admin-guide/tainted-kernels.rst +++ b/Documentation/admin-guide/tainted-kernels.rst @@ -100,6 +100,7 @@ Bit Log Number Reason that got the kernel tainted 15 _/K 32768 kernel has been live patched 16 _/X 65536 auxiliary taint, defined for and used by distros 17 _/T 131072 kernel was built with the struct randomization plugin
- 18 _/N 262144 an in-kernel test (such as a KUnit test) has been run
I think mentioning just kunit fuzzes its interpretation here. Best to keep that out.
Other than that:
Acked-by: Luis Chamberlain mcgrof@kernel.org
Luis
On Fri, May 13, 2022 at 4:32 AM David Gow davidgow@google.com wrote:
Most in-kernel tests (such as KUnit tests) are not supposed to run on production systems: they may do deliberately illegal things to trigger errors, and have security implications (for example, KUnit assertions will often deliberately leak kernel addresses).
Add a new taint type, TAINT_TEST to signal that a test has been run. This will be printed as 'N' (originally for kuNit, as every other sensible letter was taken.)
This should discourage people from running these tests on production systems, and to make it easier to tell if tests have been run accidentally (by loading the wrong configuration, etc.)
Signed-off-by: David Gow davidgow@google.com
Aside from Luis' comment (which I agree with), this looks good. I am not an expert on the taint mechanism, but this seems pretty straightforward.
Reviewed-by: Brendan Higgins brendanhiggins@google.com
Make KUnit trigger the new TAINT_TEST taint when any KUnit test is run. Due to KUnit tests not being intended to run on production systems, and potentially causing problems (or security issues like leaking kernel addresses), the kernel's state should not be considered safe for production use after KUnit tests are run.
Signed-off-by: David Gow davidgow@google.com --- lib/kunit/test.c | 4 ++++ 1 file changed, 4 insertions(+)
diff --git a/lib/kunit/test.c b/lib/kunit/test.c index 0f66c13d126e..2b808117bd4a 100644 --- a/lib/kunit/test.c +++ b/lib/kunit/test.c @@ -11,6 +11,7 @@ #include <kunit/test-bug.h> #include <linux/kernel.h> #include <linux/moduleparam.h> +#include <linux/panic.h> #include <linux/sched/debug.h> #include <linux/sched.h>
@@ -498,6 +499,9 @@ int kunit_run_tests(struct kunit_suite *suite) struct kunit_result_stats suite_stats = { 0 }; struct kunit_result_stats total_stats = { 0 };
+ /* Taint the kernel so we know we've run tests. */ + add_taint(TAINT_TEST, LOCKDEP_STILL_OK); + kunit_print_subtest_start(suite);
kunit_suite_for_each_test_case(suite, test_case) {
On Fri, May 13, 2022 at 04:32:12PM +0800, David Gow wrote:
Make KUnit trigger the new TAINT_TEST taint when any KUnit test is run. Due to KUnit tests not being intended to run on production systems, and potentially causing problems (or security issues like leaking kernel addresses), the kernel's state should not be considered safe for production use after KUnit tests are run.
Signed-off-by: David Gow davidgow@google.com
Acked-by: Luis Chamberlain mcgrof@kernel.org
Luis
On Fri, May 13, 2022 at 1:32 AM David Gow davidgow@google.com wrote:
Make KUnit trigger the new TAINT_TEST taint when any KUnit test is run. Due to KUnit tests not being intended to run on production systems, and potentially causing problems (or security issues like leaking kernel addresses), the kernel's state should not be considered safe for production use after KUnit tests are run.
Signed-off-by: David Gow davidgow@google.com
Tested-by: Daniel Latypov dlatypov@google.com
Looks good to me.
There's an edge case where we might have 0 suites or 0 tests and we still taint the kernel, but I don't think we need to deal with that. At the start of kunit_run_tests() is the cleanest place to do this.
I wasn't quite sure where this applied, but I manually applied the changes here. Without this patch, this command exits fine: $ ./tools/testing/kunit/kunit.py run --kernel_args=panic_on_taint=0x40000
With it, I get [12:03:31] Kernel panic - not syncing: panic_on_taint set ... [12:03:31] CPU: 0 PID: 1 Comm: swapper Tainted: G N 5.17.0-00001-gea9ee5e7aed8-dirty #60
I'm a bit surprised that it prints 'G' and not 'N', but this does seem to be the right mask $ python3 -c 'print(hex(1<<18))' 0x40000 and it only takes effect when this patch is applied. I'll chalk that up to my ignorance of how taint works.
On Sat, May 14, 2022 at 3:09 AM Daniel Latypov dlatypov@google.com wrote:
On Fri, May 13, 2022 at 1:32 AM David Gow davidgow@google.com wrote:
Make KUnit trigger the new TAINT_TEST taint when any KUnit test is run. Due to KUnit tests not being intended to run on production systems, and potentially causing problems (or security issues like leaking kernel addresses), the kernel's state should not be considered safe for production use after KUnit tests are run.
Signed-off-by: David Gow davidgow@google.com
Tested-by: Daniel Latypov dlatypov@google.com
Looks good to me.
There's an edge case where we might have 0 suites or 0 tests and we still taint the kernel, but I don't think we need to deal with that. At the start of kunit_run_tests() is the cleanest place to do this.
Hmm... thinking about it, I think it might be worth not tainting if 0 suites run, but tainting if 0 tests run.
If we taint even if there are no suites present, that'll make things awkward for the "build KUnit in, but not any tests" case: the kernel would be tainted regardless. Given Android might be having the KUnit execution stuff built-in (but using modules for tests), it's probably worth not tainting there. (Though I think they have a separate way of disabling KUnit as well, so it's probably not a complete deal-breaker).
The case of having suites but no tests should still taint the kernel, as suite_init functions could still run.
Assuming that seems sensible, I'll send out a v4 with that changed.
I wasn't quite sure where this applied, but I manually applied the changes here. Without this patch, this command exits fine: $ ./tools/testing/kunit/kunit.py run --kernel_args=panic_on_taint=0x40000
With it, I get [12:03:31] Kernel panic - not syncing: panic_on_taint set ... [12:03:31] CPU: 0 PID: 1 Comm: swapper Tainted: G N
This is showing both 'G' and 'N' ('G' being the character for GPL -- i.e. the kernel is not tainted by proprietary modules: 'P').
Jani did suggest a better way of printing these in the v1 discussion (printing the actual names of taints present), which I might do in a follow-up.
5.17.0-00001-gea9ee5e7aed8-dirty #60
I'm a bit surprised that it prints 'G' and not 'N', but this does seem to be the right mask $ python3 -c 'print(hex(1<<18))' 0x40000 and it only takes effect when this patch is applied. I'll chalk that up to my ignorance of how taint works.
-- David
On Fri, May 13, 2022 at 8:04 PM David Gow davidgow@google.com wrote:
Hmm... thinking about it, I think it might be worth not tainting if 0 suites run, but tainting if 0 tests run.
If we taint even if there are no suites present, that'll make things awkward for the "build KUnit in, but not any tests" case: the kernel would be tainted regardless. Given Android might be having the KUnit
Actually, this is what the code does right now. I was wrong. If there are 0 suites => not tainted. If there are 0 tests in the suites => tainted.
For kunit being built in, it first goes through this func 206 static void kunit_exec_run_tests(struct suite_set *suite_set) 207 { 208 struct kunit_suite * const * const *suites; 209 210 kunit_print_tap_header(suite_set); 211 212 for (suites = suite_set->start; suites < suite_set->end; suites++) 213 __kunit_test_suites_init(*suites); 214 }
So for the "build KUnit in, but not any tests" case, you'll never enter that for-loop. Thus you'll never call __kunit_test_suites_init() => kunit_run_tests().
For module-based tests, we have the same behavior. If there's 0 test suites, we never enter the second loop, so we never taint. But if there's >0 suites, then we will, regardless of the # of test cases.
570 int __kunit_test_suites_init(struct kunit_suite * const * const suites) 571 { 572 unsigned int i; 573 574 for (i = 0; suites[i] != NULL; i++) { 575 kunit_init_suite(suites[i]); 576 kunit_run_tests(suites[i]); 577 } 578 return 0; 579 }
So this change should already work as intended.
execution stuff built-in (but using modules for tests), it's probably worth not tainting there. (Though I think they have a separate way of disabling KUnit as well, so it's probably not a complete deal-breaker).
The case of having suites but no tests should still taint the kernel, as suite_init functions could still run.
Yes, suite_init functions are the concern. I agree we should taint if there are >0 suites but 0 test cases.
I don't think it's worth trying to be fancy and tainting iff there >0 test cases or a suite_init/exit function ran.
Assuming that seems sensible, I'll send out a v4 with that changed.
Just to be clear: that shouldn't be necessary.
I wasn't quite sure where this applied, but I manually applied the changes here. Without this patch, this command exits fine: $ ./tools/testing/kunit/kunit.py run --kernel_args=panic_on_taint=0x40000
With it, I get [12:03:31] Kernel panic - not syncing: panic_on_taint set ... [12:03:31] CPU: 0 PID: 1 Comm: swapper Tainted: G N
This is showing both 'G' and 'N' ('G' being the character for GPL --
I just somehow missed the fact there was an 'N' at the end there. Thanks, I thought I was going crazy. I guess I was just going blind.
Daniel
On Sat, May 14, 2022 at 3:25 PM Daniel Latypov dlatypov@google.com wrote:
On Fri, May 13, 2022 at 8:04 PM David Gow davidgow@google.com wrote:
Hmm... thinking about it, I think it might be worth not tainting if 0 suites run, but tainting if 0 tests run.
If we taint even if there are no suites present, that'll make things awkward for the "build KUnit in, but not any tests" case: the kernel would be tainted regardless. Given Android might be having the KUnit
Actually, this is what the code does right now. I was wrong. If there are 0 suites => not tainted. If there are 0 tests in the suites => tainted.
For kunit being built in, it first goes through this func 206 static void kunit_exec_run_tests(struct suite_set *suite_set) 207 { 208 struct kunit_suite * const * const *suites; 209 210 kunit_print_tap_header(suite_set); 211 212 for (suites = suite_set->start; suites < suite_set->end; suites++) 213 __kunit_test_suites_init(*suites); 214 }
So for the "build KUnit in, but not any tests" case, you'll never enter that for-loop. Thus you'll never call __kunit_test_suites_init() => kunit_run_tests().
For module-based tests, we have the same behavior. If there's 0 test suites, we never enter the second loop, so we never taint. But if there's >0 suites, then we will, regardless of the # of test cases.
570 int __kunit_test_suites_init(struct kunit_suite * const * const suites) 571 { 572 unsigned int i; 573 574 for (i = 0; suites[i] != NULL; i++) { 575 kunit_init_suite(suites[i]); 576 kunit_run_tests(suites[i]); 577 } 578 return 0; 579 }
So this change should already work as intended.
execution stuff built-in (but using modules for tests), it's probably worth not tainting there. (Though I think they have a separate way of disabling KUnit as well, so it's probably not a complete deal-breaker).
The case of having suites but no tests should still taint the kernel, as suite_init functions could still run.
Yes, suite_init functions are the concern. I agree we should taint if there are >0 suites but 0 test cases.
I don't think it's worth trying to be fancy and tainting iff there >0 test cases or a suite_init/exit function ran.
Assuming that seems sensible, I'll send out a v4 with that changed.
Just to be clear: that shouldn't be necessary.
Agreed. I think the current behavior is acceptable, and should be unobtrusive to Android: Joe has a patch that introduces a kernel param which disables running KUnit tests at the suite level which would happen before this taint occurs. So the only way the taint happens is if we actually try to execute some test cases (whether or not the cases actually run).
I wasn't quite sure where this applied, but I manually applied the changes here. Without this patch, this command exits fine: $ ./tools/testing/kunit/kunit.py run --kernel_args=panic_on_taint=0x40000
With it, I get [12:03:31] Kernel panic - not syncing: panic_on_taint set ... [12:03:31] CPU: 0 PID: 1 Comm: swapper Tainted: G N
This is showing both 'G' and 'N' ('G' being the character for GPL --
I just somehow missed the fact there was an 'N' at the end there. Thanks, I thought I was going crazy. I guess I was just going blind.
Daniel
On Fri, May 13, 2022 at 4:32 AM David Gow davidgow@google.com wrote:
Make KUnit trigger the new TAINT_TEST taint when any KUnit test is run. Due to KUnit tests not being intended to run on production systems, and potentially causing problems (or security issues like leaking kernel addresses), the kernel's state should not be considered safe for production use after KUnit tests are run.
Signed-off-by: David Gow davidgow@google.com
Reviewed-by: Brendan Higgins brendanhiggins@google.com
Make any kselftest test module (using the kselftest_module framework) taint the kernel with TAINT_TEST on module load.
Note that several selftests use kernel modules which are not based on the kselftest_module framework, and so will not automatically taint the kernel. These modules will have to be manually modified if they should taint the kernel this way.
Similarly, selftests which do not load modules into the kernel generally should not taint the kernel (or possibly should only do so on failure), as it's assumed that testing from user-space should be safe. Regardless, they can write to /proc/sys/kernel/tainted if required.
Signed-off-by: David Gow davidgow@google.com --- tools/testing/selftests/kselftest_module.h | 2 ++ 1 file changed, 2 insertions(+)
diff --git a/tools/testing/selftests/kselftest_module.h b/tools/testing/selftests/kselftest_module.h index e2ea41de3f35..226e616b82e0 100644 --- a/tools/testing/selftests/kselftest_module.h +++ b/tools/testing/selftests/kselftest_module.h @@ -3,6 +3,7 @@ #define __KSELFTEST_MODULE_H
#include <linux/module.h> +#include <linux/panic.h>
/* * Test framework for writing test modules to be loaded by kselftest. @@ -41,6 +42,7 @@ static inline int kstm_report(unsigned int total_tests, unsigned int failed_test static int __init __module##_init(void) \ { \ pr_info("loaded.\n"); \ + add_taint(TAINT_KUNIT, LOCKDEP_STILL_OK); \ selftest(); \ return kstm_report(total_tests, failed_tests, skipped_tests); \ } \
On Fri, May 13, 2022 at 04:32:13PM +0800, David Gow wrote:
Make any kselftest test module (using the kselftest_module framework) taint the kernel with TAINT_TEST on module load.
Note that several selftests use kernel modules which are not based on the kselftest_module framework, and so will not automatically taint the kernel. These modules will have to be manually modified if they should taint the kernel this way.
Similarly, selftests which do not load modules into the kernel generally should not taint the kernel (or possibly should only do so on failure), as it's assumed that testing from user-space should be safe. Regardless, they can write to /proc/sys/kernel/tainted if required.
Signed-off-by: David Gow davidgow@google.com
Not all selftest modules use KSTM_MODULE_LOADERS() so I'd like to see a modpost target as well, otherwise this just covers a sliver of selftests.
Luis
On Fri, May 13, 2022 at 11:38 PM Luis Chamberlain mcgrof@kernel.org wrote:
On Fri, May 13, 2022 at 04:32:13PM +0800, David Gow wrote:
Make any kselftest test module (using the kselftest_module framework) taint the kernel with TAINT_TEST on module load.
Note that several selftests use kernel modules which are not based on the kselftest_module framework, and so will not automatically taint the kernel. These modules will have to be manually modified if they should taint the kernel this way.
Similarly, selftests which do not load modules into the kernel generally should not taint the kernel (or possibly should only do so on failure), as it's assumed that testing from user-space should be safe. Regardless, they can write to /proc/sys/kernel/tainted if required.
Signed-off-by: David Gow davidgow@google.com
Not all selftest modules use KSTM_MODULE_LOADERS() so I'd like to see a modpost target as well, otherwise this just covers a sliver of selftests.
My personal feeling is that the ideal way of solving this is actually to port those modules which aren't using KSTM_MODULE_LOADERS() (or KUnit, or some other system) to do so, or to otherwise manually tag them as selftests and/or make them taint the kernel.
That being said, we can gain a bit my making the module-loading helpers in kselftest/module.sh manually taint the kernel with /proc/sys/kernel/tainted, which will catch quite a few of them (even if tainting from userspace before they're loaded is suboptimal).
I've also started experimenting with a "test" MODULE_INFO field, which modpost would add with the -t option. That still requires sprinkling MODULE_INFO() everwhere, or the '-t' option to a bunch of makefiles, or doing something more drastic to set it automatically for modules in a given directory / makefile. Or the staging thing of checking the directory / prefix in modpost.
I'll play around some more and have something to show in v4. (If we have a MODULE_INFO field, we should use it for KUnit modules, but we'd still have to taint the kernel manually for built-in tests anyway, so it'd be redundant...)
-- David
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