The patch titled
Subject: mm/kmemleak: avoid scanning potential huge holes
has been added to the -mm tree. Its filename is
mm-kmemleak-avoid-scanning-potential-huge-holes.patch
This patch should soon appear at
https://ozlabs.org/~akpm/mmots/broken-out/mm-kmemleak-avoid-scanning-potent…
and later at
https://ozlabs.org/~akpm/mmotm/broken-out/mm-kmemleak-avoid-scanning-potent…
Before you just go and hit "reply", please:
a) Consider who else should be cc'ed
b) Prefer to cc a suitable mailing list as well
c) Ideally: find the original patch on the mailing list and do a
reply-to-all to that, adding suitable additional cc's
*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next and is updated
there every 3-4 working days
------------------------------------------------------
From: Lang Yu <lang.yu(a)amd.com>
Subject: mm/kmemleak: avoid scanning potential huge holes
When using devm_request_free_mem_region() and devm_memremap_pages() to add
ZONE_DEVICE memory, if requested free mem region's end pfn were huge(e.g.,
0x400000000), the node_end_pfn() will be also huge (see
move_pfn_range_to_zone()). Thus it creates a huge hole between
node_start_pfn() and node_end_pfn().
We found on some AMD APUs, amdkfd requested such a free mem region and
created a huge hole. In such a case, following code snippet was just
doing busy test_bit() looping on the huge hole.
for (pfn = start_pfn; pfn < end_pfn; pfn++) {
struct page *page = pfn_to_online_page(pfn);
if (!page)
continue;
...
}
So we got a soft lockup:
watchdog: BUG: soft lockup - CPU#6 stuck for 26s! [bash:1221]
CPU: 6 PID: 1221 Comm: bash Not tainted 5.15.0-custom #1
RIP: 0010:pfn_to_online_page+0x5/0xd0
Call Trace:
? kmemleak_scan+0x16a/0x440
kmemleak_write+0x306/0x3a0
? common_file_perm+0x72/0x170
full_proxy_write+0x5c/0x90
vfs_write+0xb9/0x260
ksys_write+0x67/0xe0
__x64_sys_write+0x1a/0x20
do_syscall_64+0x3b/0xc0
entry_SYSCALL_64_after_hwframe+0x44/0xae
I did some tests with the patch.
(1) amdgpu module unloaded
before the patch:
real 0m0.976s
user 0m0.000s
sys 0m0.968s
after the patch:
real 0m0.981s
user 0m0.000s
sys 0m0.973s
(2) amdgpu module loaded
before the patch:
real 0m35.365s
user 0m0.000s
sys 0m35.354s
after the patch:
real 0m1.049s
user 0m0.000s
sys 0m1.042s
Link: https://lkml.kernel.org/r/20211108140029.721144-1-lang.yu@amd.com
Signed-off-by: Lang Yu <lang.yu(a)amd.com>
Acked-by: David Hildenbrand <david(a)redhat.com>
Acked-by: Catalin Marinas <catalin.marinas(a)arm.com>
Cc: Oscar Salvador <osalvador(a)suse.de>
Cc: <stable(a)vger.kernel.org>
Signed-off-by: Andrew Morton <akpm(a)linux-foundation.org>
---
mm/kmemleak.c | 13 +++++++------
1 file changed, 7 insertions(+), 6 deletions(-)
--- a/mm/kmemleak.c~mm-kmemleak-avoid-scanning-potential-huge-holes
+++ a/mm/kmemleak.c
@@ -1410,7 +1410,8 @@ static void kmemleak_scan(void)
{
unsigned long flags;
struct kmemleak_object *object;
- int i;
+ struct zone *zone;
+ int __maybe_unused i;
int new_leaks = 0;
jiffies_last_scan = jiffies;
@@ -1450,9 +1451,9 @@ static void kmemleak_scan(void)
* Struct page scanning for each node.
*/
get_online_mems();
- for_each_online_node(i) {
- unsigned long start_pfn = node_start_pfn(i);
- unsigned long end_pfn = node_end_pfn(i);
+ for_each_populated_zone(zone) {
+ unsigned long start_pfn = zone->zone_start_pfn;
+ unsigned long end_pfn = zone_end_pfn(zone);
unsigned long pfn;
for (pfn = start_pfn; pfn < end_pfn; pfn++) {
@@ -1461,8 +1462,8 @@ static void kmemleak_scan(void)
if (!page)
continue;
- /* only scan pages belonging to this node */
- if (page_to_nid(page) != i)
+ /* only scan pages belonging to this zone */
+ if (page_zone(page) != zone)
continue;
/* only scan if page is in use */
if (page_count(page) == 0)
_
Patches currently in -mm which might be from lang.yu(a)amd.com are
mm-kmemleak-avoid-scanning-potential-huge-holes.patch
The patch titled
Subject: exec: force single empty string when argv is empty
has been added to the -mm tree. Its filename is
exec-force-single-empty-string-when-argv-is-empty.patch
This patch should soon appear at
https://ozlabs.org/~akpm/mmots/broken-out/exec-force-single-empty-string-wh…
and later at
https://ozlabs.org/~akpm/mmotm/broken-out/exec-force-single-empty-string-wh…
Before you just go and hit "reply", please:
a) Consider who else should be cc'ed
b) Prefer to cc a suitable mailing list as well
c) Ideally: find the original patch on the mailing list and do a
reply-to-all to that, adding suitable additional cc's
*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next and is updated
there every 3-4 working days
------------------------------------------------------
From: Kees Cook <keescook(a)chromium.org>
Subject: exec: force single empty string when argv is empty
Quoting[1] Ariadne Conill:
"In several other operating systems, it is a hard requirement that the
second argument to execve(2) be the name of a program, thus prohibiting
a scenario where argc < 1. POSIX 2017 also recommends this behaviour,
but it is not an explicit requirement[2]:
The argument arg0 should point to a filename string that is
associated with the process being started by one of the exec
functions.
...
Interestingly, Michael Kerrisk opened an issue about this in 2008[3],
but there was no consensus to support fixing this issue then.
Hopefully now that CVE-2021-4034 shows practical exploitative use[4]
of this bug in a shellcode, we can reconsider.
This issue is being tracked in the KSPP issue tracker[5]."
While the initial code searches[6][7] turned up what appeared to be
mostly corner case tests, trying to that just reject argv == NULL
(or an immediately terminated pointer list) quickly started tripping[8]
existing userspace programs.
The next best approach is forcing a single empty string into argv and
adjusting argc to match. The number of programs depending on argc == 0
seems a smaller set than those calling execve with a NULL argv.
Account for the additional stack space in bprm_stack_limits(). Inject an
empty string when argc == 0 (and set argc = 1). Warn about the case so
userspace has some notice about the change:
process './argc0' launched './argc0' with NULL argv: empty string added
Additionally WARN() and reject NULL argv usage for kernel threads.
[1] https://lore.kernel.org/lkml/20220127000724.15106-1-ariadne@dereferenced.or…
[2] https://pubs.opengroup.org/onlinepubs/9699919799/functions/exec.html
[3] https://bugzilla.kernel.org/show_bug.cgi?id=8408
[4] https://www.qualys.com/2022/01/25/cve-2021-4034/pwnkit.txt
[5] https://github.com/KSPP/linux/issues/176
[6] https://codesearch.debian.net/search?q=execve%5C+*%5C%28%5B%5E%2C%5D%2B%2C+…
[7] https://codesearch.debian.net/search?q=execlp%3F%5Cs*%5C%28%5B%5E%2C%5D%2B%…
[8] https://lore.kernel.org/lkml/20220131144352.GE16385@xsang-OptiPlex-9020/
Link: https://lkml.kernel.org/r/20220201000947.2453721-1-keescook@chromium.org
Signed-off-by: Kees Cook <keescook(a)chromium.org>Reported-by: Ariadne Conill <ariadne(a)dereferenced.org>
Reported-by: Michael Kerrisk <mtk.manpages(a)gmail.com>
Cc: Matthew Wilcox <willy(a)infradead.org>
Cc: Christian Brauner <brauner(a)kernel.org>
Cc: Rich Felker <dalias(a)libc.org>
Cc: Eric Biederman <ebiederm(a)xmission.com>
Cc: Alexander Viro <viro(a)zeniv.linux.org.uk>
Cc: <stable(a)vger.kernel.org>
Signed-off-by: Andrew Morton <akpm(a)linux-foundation.org>
---
fs/exec.c | 26 +++++++++++++++++++++++++-
1 file changed, 25 insertions(+), 1 deletion(-)
--- a/fs/exec.c~exec-force-single-empty-string-when-argv-is-empty
+++ a/fs/exec.c
@@ -495,8 +495,14 @@ static int bprm_stack_limits(struct linu
* the stack. They aren't stored until much later when we can't
* signal to the parent that the child has run out of stack space.
* Instead, calculate it here so it's possible to fail gracefully.
+ *
+ * In the case of argc = 0, make sure there is space for adding a
+ * empty string (which will bump argc to 1), to ensure confused
+ * userspace programs don't start processing from argv[1], thinking
+ * argc can never be 0, to keep them from walking envp by accident.
+ * See do_execveat_common().
*/
- ptr_size = (bprm->argc + bprm->envc) * sizeof(void *);
+ ptr_size = (min(bprm->argc, 1) + bprm->envc) * sizeof(void *);
if (limit <= ptr_size)
return -E2BIG;
limit -= ptr_size;
@@ -1897,6 +1903,9 @@ static int do_execveat_common(int fd, st
}
retval = count(argv, MAX_ARG_STRINGS);
+ if (retval == 0)
+ pr_warn_once("process '%s' launched '%s' with NULL argv: empty string added\n",
+ current->comm, bprm->filename);
if (retval < 0)
goto out_free;
bprm->argc = retval;
@@ -1923,6 +1932,19 @@ static int do_execveat_common(int fd, st
if (retval < 0)
goto out_free;
+ /*
+ * When argv is empty, add an empty string ("") as argv[0] to
+ * ensure confused userspace programs that start processing
+ * from argv[1] won't end up walking envp. See also
+ * bprm_stack_limits().
+ */
+ if (bprm->argc == 0) {
+ retval = copy_string_kernel("", bprm);
+ if (retval < 0)
+ goto out_free;
+ bprm->argc = 1;
+ }
+
retval = bprm_execve(bprm, fd, filename, flags);
out_free:
free_bprm(bprm);
@@ -1951,6 +1973,8 @@ int kernel_execve(const char *kernel_fil
}
retval = count_strings_kernel(argv);
+ if (WARN_ON_ONCE(retval == 0))
+ retval = -EINVAL;
if (retval < 0)
goto out_free;
bprm->argc = retval;
_
Patches currently in -mm which might be from keescook(a)chromium.org are
kconfigdebug-make-debug_info-selectable-from-a-choice.patch
kconfigdebug-make-debug_info-selectable-from-a-choice-fix.patch
exec-force-single-empty-string-when-argv-is-empty.patch
The patch titled
Subject: fs/exec: require argv[0] presence in do_execveat_common()
has been removed from the -mm tree. Its filename was
fs-exec-require-argv-presence-in-do_execveat_common.patch
This patch was dropped because an alternative patch was merged
------------------------------------------------------
From: Ariadne Conill <ariadne(a)dereferenced.org>
Subject: fs/exec: require argv[0] presence in do_execveat_common()
In several other operating systems, it is a hard requirement that the
second argument to execve(2) be the name of a program, thus prohibiting a
scenario where argc < 1. POSIX 2017 also recommends this behaviour, but
it is not an explicit requirement[0]:
The argument arg0 should point to a filename string that is
associated with the process being started by one of the exec
functions.
To ensure that execve(2) with argc < 1 is not a useful tool for shellcode
to use, we can validate this in do_execveat_common() and fail for this
scenario, effectively blocking successful exploitation of CVE-2021-4034
and similar bugs which depend on execve(2) working with argc < 1.
We use -EINVAL for this case, mirroring recent changes to FreeBSD and
OpenBSD. -EINVAL is also used by QNX for this, while Solaris uses
-EFAULT.
In earlier versions of the patch, it was proposed that we create a fake
argv for applications to use when argc < 1, but it was concluded that it
would be better to just fail the execve(2) in these cases, as launching a
process with an empty or NULL argv[0] was likely to just cause more
problems.
Interestingly, Michael Kerrisk opened an issue about this in 2008[1], but
there was no consensus to support fixing this issue then. Hopefully now
that CVE-2021-4034 shows practical exploitative use[2] of this bug in a
shellcode, we can reconsider.
This issue is being tracked in the KSPP issue tracker[3].
There are a few[4][5] minor edge cases (primarily in test suites) that are
caught by this, but we plan to work with the projects to fix those edge
cases.
[0]: https://pubs.opengroup.org/onlinepubs/9699919799/functions/exec.html
[1]: https://bugzilla.kernel.org/show_bug.cgi?id=8408
[2]: https://www.qualys.com/2022/01/25/cve-2021-4034/pwnkit.txt
[3]: https://github.com/KSPP/linux/issues/176
[4]: https://codesearch.debian.net/search?q=execve%5C+*%5C%28%5B%5E%2C%5D%2B%2C+…
[5]: https://codesearch.debian.net/search?q=execlp%3F%5Cs*%5C%28%5B%5E%2C%5D%2B%…
Link: https://lkml.kernel.org/r/20220127000724.15106-1-ariadne@dereferenced.org
Signed-off-by: Ariadne Conill <ariadne(a)dereferenced.org>
Reported-by: Michael Kerrisk <mtk.manpages(a)gmail.com>
Cc: Matthew Wilcox <willy(a)infradead.org>
Cc: Christian Brauner <brauner(a)kernel.org>
Cc: Rich Felker <dalias(a)libc.org>
Cc: Eric Biederman <ebiederm(a)xmission.com>
Cc: Alexander Viro <viro(a)zeniv.linux.org.uk>
Cc: Kees Cook <keescook(a)chromium.org>
Cc: <stable(a)vger.kernel.org>
Signed-off-by: Andrew Morton <akpm(a)linux-foundation.org>
---
fs/exec.c | 4 ++++
1 file changed, 4 insertions(+)
--- a/fs/exec.c~fs-exec-require-argv-presence-in-do_execveat_common
+++ a/fs/exec.c
@@ -1897,6 +1897,10 @@ static int do_execveat_common(int fd, st
}
retval = count(argv, MAX_ARG_STRINGS);
+ if (retval == 0) {
+ pr_warn_once("Attempted to run process '%s' with NULL argv\n", bprm->filename);
+ retval = -EINVAL;
+ }
if (retval < 0)
goto out_free;
bprm->argc = retval;
_
Patches currently in -mm which might be from ariadne(a)dereferenced.org are