v3: - use the quotes with correct format in the commit message of patch 4/4, sorry for that
Tiezhu Yang (4): selftests: kmod: Use variable NAME in kmod_test_0001() kmod: Remove redundant "be an" in the comment kmod: Return directly if module name is empty in request_module() test_kmod: Avoid potential double free in trigger_config_run_type()
kernel/kmod.c | 10 +++++++--- lib/test_kmod.c | 2 +- tools/testing/selftests/kmod/kmod.sh | 4 ++-- 3 files changed, 10 insertions(+), 6 deletions(-)
Use the variable NAME instead of "\000" directly in kmod_test_0001().
Acked-by: Luis Chamberlain mcgrof@kernel.org Signed-off-by: Tiezhu Yang yangtiezhu@loongson.cn ---
v3: - no changes
v2: - just add the Acked-by tag
tools/testing/selftests/kmod/kmod.sh | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/tools/testing/selftests/kmod/kmod.sh b/tools/testing/selftests/kmod/kmod.sh index 3702dbc..da60c3b 100755 --- a/tools/testing/selftests/kmod/kmod.sh +++ b/tools/testing/selftests/kmod/kmod.sh @@ -341,7 +341,7 @@ kmod_test_0001_driver()
kmod_defaults_driver config_num_threads 1 - printf '\000' >"$DIR"/config_test_driver + printf $NAME >"$DIR"/config_test_driver config_trigger ${FUNCNAME[0]} config_expect_result ${FUNCNAME[0]} MODULE_NOT_FOUND } @@ -352,7 +352,7 @@ kmod_test_0001_fs()
kmod_defaults_fs config_num_threads 1 - printf '\000' >"$DIR"/config_test_fs + printf $NAME >"$DIR"/config_test_fs config_trigger ${FUNCNAME[0]} config_expect_result ${FUNCNAME[0]} -EINVAL }
There exists redundant "be an" in the comment, remove it.
Acked-by: Luis Chamberlain mcgrof@kernel.org Signed-off-by: Tiezhu Yang yangtiezhu@loongson.cn ---
v3: - no changes
v2: - just add the Acked-by tag
kernel/kmod.c | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-)
diff --git a/kernel/kmod.c b/kernel/kmod.c index 37c3c4b..3cd075c 100644 --- a/kernel/kmod.c +++ b/kernel/kmod.c @@ -36,9 +36,8 @@ * * If you need less than 50 threads would mean we're dealing with systems * smaller than 3200 pages. This assumes you are capable of having ~13M memory, - * and this would only be an be an upper limit, after which the OOM killer - * would take effect. Systems like these are very unlikely if modules are - * enabled. + * and this would only be an upper limit, after which the OOM killer would take + * effect. Systems like these are very unlikely if modules are enabled. */ #define MAX_KMOD_CONCURRENT 50 static atomic_t kmod_concurrent_max = ATOMIC_INIT(MAX_KMOD_CONCURRENT);
If module name is empty, it is better to return directly at the beginning of request_module() without doing the needless call_modprobe() operation.
Call trace:
request_module() | | __request_module() | | call_modprobe() | | call_usermodehelper_exec() -- retval = sub_info->retval; | | call_usermodehelper_exec_work() | | call_usermodehelper_exec_sync() -- sub_info->retval = ret; | | --> call_usermodehelper_exec_async() --> do_execve() | kernel_wait4(pid, (int __user *)&ret, 0, NULL);
sub_info->retval is 256 after call kernel_wait4(), the function call_usermodehelper_exec() returns sub_info->retval which is 256, then call_modprobe() and __request_module() returns 256.
Signed-off-by: Tiezhu Yang yangtiezhu@loongson.cn ---
v3: - no changes
v2: - update the commit message to explain the detailed reason
kernel/kmod.c | 5 +++++ 1 file changed, 5 insertions(+)
diff --git a/kernel/kmod.c b/kernel/kmod.c index 3cd075c..5851444 100644 --- a/kernel/kmod.c +++ b/kernel/kmod.c @@ -28,6 +28,8 @@
#include <trace/events/module.h>
+#define MODULE_NOT_FOUND 256 + /* * Assuming: * @@ -144,6 +146,9 @@ int __request_module(bool wait, const char *fmt, ...) if (ret >= MODULE_NAME_LEN) return -ENAMETOOLONG;
+ if (strlen(module_name) == 0) + return MODULE_NOT_FOUND; + ret = security_kernel_module_request(module_name); if (ret) return ret;
On Mon, Apr 20, 2020 at 08:33:54PM +0800, Tiezhu Yang wrote:
If module name is empty, it is better to return directly at the beginning of request_module() without doing the needless call_modprobe() operation.
Call trace:
request_module() | | __request_module() | | call_modprobe() | | call_usermodehelper_exec() -- retval = sub_info->retval; | | call_usermodehelper_exec_work() | | call_usermodehelper_exec_sync() -- sub_info->retval = ret; | | --> call_usermodehelper_exec_async() --> do_execve() | kernel_wait4(pid, (int __user *)&ret, 0, NULL);
sub_info->retval is 256 after call kernel_wait4(), the function call_usermodehelper_exec() returns sub_info->retval which is 256, then call_modprobe() and __request_module() returns 256.
Signed-off-by: Tiezhu Yang yangtiezhu@loongson.cn
Thanks for looking into this. I still cannot find where userspace it returns 256. Can you? If I run modprobe without an argument I see 1 returned.
At least kmod [0] has a series of cmd helper structs, the one for modprobe seems to be kmod_cmd_compat_modprobe, and I can see -1 returned which can be converted to 255. It can also return EXIT_FAILURE or EXIT_SUCCESS and /usr/include/stdlib.h defines these as 1 and 0 respectively.
https://git.kernel.org/pub/scm/utils/kernel/kmod/kmod.git/
Luis
On 04/21/2020 02:19 AM, Luis Chamberlain wrote:
On Mon, Apr 20, 2020 at 08:33:54PM +0800, Tiezhu Yang wrote:
If module name is empty, it is better to return directly at the beginning of request_module() without doing the needless call_modprobe() operation.
Call trace:
request_module() | | __request_module() | | call_modprobe() | | call_usermodehelper_exec() -- retval = sub_info->retval; | | call_usermodehelper_exec_work() | | call_usermodehelper_exec_sync() -- sub_info->retval = ret; | | --> call_usermodehelper_exec_async() --> do_execve() | kernel_wait4(pid, (int __user *)&ret, 0, NULL);
sub_info->retval is 256 after call kernel_wait4(), the function call_usermodehelper_exec() returns sub_info->retval which is 256, then call_modprobe() and __request_module() returns 256.
Signed-off-by: Tiezhu Yang yangtiezhu@loongson.cn
Thanks for looking into this. I still cannot find where userspace it returns 256. Can you? If I run modprobe without an argument I see 1 returned.
At least kmod [0] has a series of cmd helper structs, the one for modprobe seems to be kmod_cmd_compat_modprobe, and I can see -1 returned which can be converted to 255. It can also return EXIT_FAILURE or EXIT_SUCCESS and /usr/include/stdlib.h defines these as 1 and 0 respectively.
https://git.kernel.org/pub/scm/utils/kernel/kmod/kmod.git/
Luis
Here is my understanding:
When build and execute the following application, we can see the exit status is 256.
$ ./system modprobe: FATAL: Module not found in directory /lib/modules/4.18.0-147.5.1.el8_1.x86_64 exit status = 256
$ ./execl modprobe: FATAL: Module not found in directory /lib/modules/4.18.0-147.5.1.el8_1.x86_64 exit status = 256
$ cat system.c #include <stdio.h> #include <stdlib.h>
int main() { int status = 0;
status = system("modprobe ''"); printf("exit status = %d\n", status);
return status; }
$ cat execl.c #include <sys/wait.h> #include <stdlib.h> #include <unistd.h> #include <stdio.h>
int main() { pid_t pid, w; int status;
pid = fork(); if (pid == -1) { perror("fork"); exit(EXIT_FAILURE); }
if (pid == 0) { execl("/bin/sh", "sh", "-c", "modprobe aaa", (char *) 0); } else { w = waitpid(pid, &status, 0); if (w == -1) { perror("waitpid"); exit(EXIT_FAILURE); }
printf("exit status = %d\n", status);
exit(EXIT_SUCCESS); }
return 0; }
The exit status of child process is wrote to the address of variable "status" after call waitpid()in the user space that correspond with kernel_wait4() [1] in the kernel space.
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/kern...
+++ Tiezhu Yang [21/04/20 11:07 +0800]:
On 04/21/2020 02:19 AM, Luis Chamberlain wrote:
On Mon, Apr 20, 2020 at 08:33:54PM +0800, Tiezhu Yang wrote:
If module name is empty, it is better to return directly at the beginning of request_module() without doing the needless call_modprobe() operation.
Call trace:
request_module() | | __request_module() | | call_modprobe() | | call_usermodehelper_exec() -- retval = sub_info->retval; | | call_usermodehelper_exec_work() | | call_usermodehelper_exec_sync() -- sub_info->retval = ret; | | --> call_usermodehelper_exec_async() --> do_execve() | kernel_wait4(pid, (int __user *)&ret, 0, NULL);
sub_info->retval is 256 after call kernel_wait4(), the function call_usermodehelper_exec() returns sub_info->retval which is 256, then call_modprobe() and __request_module() returns 256.
Signed-off-by: Tiezhu Yang yangtiezhu@loongson.cn
Thanks for looking into this. I still cannot find where userspace it returns 256. Can you? If I run modprobe without an argument I see 1 returned.
At least kmod [0] has a series of cmd helper structs, the one for modprobe seems to be kmod_cmd_compat_modprobe, and I can see -1 returned which can be converted to 255. It can also return EXIT_FAILURE or EXIT_SUCCESS and /usr/include/stdlib.h defines these as 1 and 0 respectively.
I'm also seeing modprobe return 1 as exit status when I run it without arguments. I don't think the 256 value is coming from modprobe though, see below -
https://git.kernel.org/pub/scm/utils/kernel/kmod/kmod.git/
Luis
Here is my understanding:
When build and execute the following application, we can see the exit status is 256.
$ ./system modprobe: FATAL: Module not found in directory /lib/modules/4.18.0-147.5.1.el8_1.x86_64 exit status = 256
$ ./execl modprobe: FATAL: Module not found in directory /lib/modules/4.18.0-147.5.1.el8_1.x86_64 exit status = 256
I am going to guess this has something to do with how system() and waitpid() (and the wait family of syscalls in general) encode the exit status in their return values. According to their man pages, you need to use the appropriate WIF* macros to get the actual exit code of the child process.
From system(3):
the return value is a "wait status" that can be examined using the macros described in waitpid(2). (i.e., WIFEXITED(), WEXITSTATUS(), and so on)
From waitpid(2):
If wstatus is not NULL, wait() and waitpid() store status information in the int to which it points. This integer can be inspected with the following macros (which take the integer itself as an argument, not a pointer to it, as is done in wait() and waitpid()!):
WEXITSTATUS(wstatus) returns the exit status of the child. This consists of the least significant 8 bits of the status argument that the child specified in a call to exit(3) or _exit(2) or as the argument for a return statement in main(). This macro should be employed only if WIFEXITED returned true.
In your test code, you are reading &status directly. To obtain the exit status, you need to use WEXITSTATUS(status), or right shift the value by 8 bits. That gives you 1, which was the original exit code given by modprobe. That's why you see an exit code of 1 when running modprobe directly and you see 256 when using system() and waitpid() and don't use the WIF* macros.
As for why __request_module() returns 256, I am guessing this would come from kernel_wait4(), but I did not dive into the call path to verify this yet.
Jessica
On Tue, Apr 21, 2020 at 04:49:32PM +0200, Jessica Yu wrote:
As for why __request_module() returns 256, I am guessing this would come from kernel_wait4(), but I did not dive into the call path to verify this yet.
I got it. I'll send a fix.
Luis
On 04/21/2020 10:49 PM, Jessica Yu wrote:
+++ Tiezhu Yang [21/04/20 11:07 +0800]:
On 04/21/2020 02:19 AM, Luis Chamberlain wrote:
On Mon, Apr 20, 2020 at 08:33:54PM +0800, Tiezhu Yang wrote:
If module name is empty, it is better to return directly at the beginning of request_module() without doing the needless call_modprobe() operation.
Call trace:
request_module() | | __request_module() | | call_modprobe() | | call_usermodehelper_exec() -- retval = sub_info->retval; | | call_usermodehelper_exec_work() | | call_usermodehelper_exec_sync() -- sub_info->retval = ret; | | --> call_usermodehelper_exec_async() --> do_execve() | kernel_wait4(pid, (int __user *)&ret, 0, NULL);
sub_info->retval is 256 after call kernel_wait4(), the function call_usermodehelper_exec() returns sub_info->retval which is 256, then call_modprobe() and __request_module() returns 256.
Signed-off-by: Tiezhu Yang yangtiezhu@loongson.cn
Thanks for looking into this. I still cannot find where userspace it returns 256. Can you? If I run modprobe without an argument I see 1 returned.
At least kmod [0] has a series of cmd helper structs, the one for modprobe seems to be kmod_cmd_compat_modprobe, and I can see -1 returned which can be converted to 255. It can also return EXIT_FAILURE or EXIT_SUCCESS and /usr/include/stdlib.h defines these as 1 and 0 respectively.
I'm also seeing modprobe return 1 as exit status when I run it without arguments. I don't think the 256 value is coming from modprobe though, see below -
https://git.kernel.org/pub/scm/utils/kernel/kmod/kmod.git/
Luis
Here is my understanding:
When build and execute the following application, we can see the exit status is 256.
$ ./system modprobe: FATAL: Module not found in directory /lib/modules/4.18.0-147.5.1.el8_1.x86_64 exit status = 256
$ ./execl modprobe: FATAL: Module not found in directory /lib/modules/4.18.0-147.5.1.el8_1.x86_64 exit status = 256
I am going to guess this has something to do with how system() and waitpid() (and the wait family of syscalls in general) encode the exit status in their return values. According to their man pages, you need to use the appropriate WIF* macros to get the actual exit code of the child process.
From system(3):
the return value is a "wait status" that can be examined using the macros described in waitpid(2). (i.e., WIFEXITED(), WEXITSTATUS(), and so on)
From waitpid(2):
If wstatus is not NULL, wait() and waitpid() store status information in the int to which it points. This integer can be inspected with the following macros (which take the integer itself as an argument, not a pointer to it, as is done in wait() and waitpid()!): WEXITSTATUS(wstatus) returns the exit status of the child. This consists of the least significant 8 bits of the status argument that the child specified in a call to exit(3) or _exit(2) or as the argument for a return statement in main(). This macro should be employed only if WIFEXITED returned true.In your test code, you are reading &status directly. To obtain the exit status, you need to use WEXITSTATUS(status), or right shift the value by 8 bits. That gives you 1, which was the original exit code given by modprobe. That's why you see an exit code of 1 when running modprobe directly and you see 256 when using system() and waitpid() and don't use the WIF* macros.
As for why __request_module() returns 256, I am guessing this would come from kernel_wait4(), but I did not dive into the call path to verify this yet.
+Cc Al Viro viro@zeniv.linux.org.uk
Hi Al,
When module name is empty, __request_module() returns 256. What do you think about this case and patch? Thank you very much for your attention.
patch v3: https://lore.kernel.org/patchwork/patch/1227274/
patch v4 (update the commit message): https://lore.kernel.org/patchwork/patch/1227981/
Jessica
On Wed, Apr 22, 2020 at 04:55:34PM +0800, Tiezhu Yang wrote:
On 04/21/2020 10:49 PM, Jessica Yu wrote:
+++ Tiezhu Yang [21/04/20 11:07 +0800]:
On 04/21/2020 02:19 AM, Luis Chamberlain wrote:
On Mon, Apr 20, 2020 at 08:33:54PM +0800, Tiezhu Yang wrote:
If module name is empty, it is better to return directly at the beginning of request_module() without doing the needless call_modprobe() operation.
Call trace:
request_module() | | __request_module() | | call_modprobe() | | call_usermodehelper_exec() -- retval = sub_info->retval; | | call_usermodehelper_exec_work() | | call_usermodehelper_exec_sync() -- sub_info->retval = ret; | | --> call_usermodehelper_exec_async() --> do_execve() | kernel_wait4(pid, (int __user *)&ret, 0, NULL);
sub_info->retval is 256 after call kernel_wait4(), the function call_usermodehelper_exec() returns sub_info->retval which is 256, then call_modprobe() and __request_module() returns 256.
Signed-off-by: Tiezhu Yang yangtiezhu@loongson.cn
Thanks for looking into this. I still cannot find where userspace it returns 256. Can you? If I run modprobe without an argument I see 1 returned.
At least kmod [0] has a series of cmd helper structs, the one for modprobe seems to be kmod_cmd_compat_modprobe, and I can see -1 returned which can be converted to 255. It can also return EXIT_FAILURE or EXIT_SUCCESS and /usr/include/stdlib.h defines these as 1 and 0 respectively.
I'm also seeing modprobe return 1 as exit status when I run it without arguments. I don't think the 256 value is coming from modprobe though, see below -
https://git.kernel.org/pub/scm/utils/kernel/kmod/kmod.git/
Luis
Here is my understanding:
When build and execute the following application, we can see the exit status is 256.
$ ./system modprobe: FATAL: Module not found in directory /lib/modules/4.18.0-147.5.1.el8_1.x86_64 exit status = 256
$ ./execl modprobe: FATAL: Module not found in directory /lib/modules/4.18.0-147.5.1.el8_1.x86_64 exit status = 256
I am going to guess this has something to do with how system() and waitpid() (and the wait family of syscalls in general) encode the exit status in their return values. According to their man pages, you need to use the appropriate WIF* macros to get the actual exit code of the child process.
From system(3):
the return value is a "wait status" that can be examined using the macros described in waitpid(2). (i.e., WIFEXITED(), WEXITSTATUS(), and so on)
From waitpid(2):
If wstatus is not NULL, wait() and waitpid() store status information in the int to which it points. This integer can be inspected with the following macros (which take the integer itself as an argument, not a pointer to it, as is done in wait() and waitpid()!): WEXITSTATUS(wstatus) returns the exit status of the child. This consists of the least significant 8 bits of the status argument that the child specified in a call to exit(3) or _exit(2) or as the argument for a return statement in main(). This macro should be employed only if WIFEXITED returned true.In your test code, you are reading &status directly. To obtain the exit status, you need to use WEXITSTATUS(status), or right shift the value by 8 bits. That gives you 1, which was the original exit code given by modprobe. That's why you see an exit code of 1 when running modprobe directly and you see 256 when using system() and waitpid() and don't use the WIF* macros.
As for why __request_module() returns 256, I am guessing this would come from kernel_wait4(), but I did not dive into the call path to verify this yet.
+Cc Al Viro viro@zeniv.linux.org.uk
Hi Al,
When module name is empty, __request_module() returns 256. What do you think about this case and patch? Thank you very much for your attention.
Its because of an old issue umh.c, I'll send a patch.
Luis
Reset the member "test_fs" of the test configuration after a call of the function "kfree_const" to a null pointer so that a double memory release will not be performed.
Fixes: d9c6a72d6fa2 ("kmod: add test driver to stress test the module loader") Acked-by: Luis Chamberlain mcgrof@kernel.org Signed-off-by: Tiezhu Yang yangtiezhu@loongson.cn ---
v3: - use the quotes with correct format in the commit message, sorry for that
v2: - update the commit message suggested by Markus Elfring - add the Fixes tag
lib/test_kmod.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/lib/test_kmod.c b/lib/test_kmod.c index e651c37..eab5277 100644 --- a/lib/test_kmod.c +++ b/lib/test_kmod.c @@ -745,7 +745,7 @@ static int trigger_config_run_type(struct kmod_test_device *test_dev, break; case TEST_KMOD_FS_TYPE: kfree_const(config->test_fs); - config->test_driver = NULL; + config->test_fs = NULL; copied = config_copy_test_fs(config, test_str, strlen(test_str)); break;
linux-kselftest-mirror@lists.linaro.org
-
Jessica Yu -
Luis Chamberlain -
Tiezhu Yang