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| author | Jann Horn <jannh@google.com> | 2019-02-27 21:29:52 +0100 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2019-02-27 17:27:02 -0800 |
| commit | 0a1d52994d440e21def1c2174932410b4f2a98a1 (patch) | |
| tree | 0674c4cb793d0402ce24061f8db61d04024d1a88 /mm/mmap.c | |
| parent | 7d762d69145a54d169f58e56d6dac57a5508debc (diff) | |
| download | linux-0a1d52994d440e21def1c2174932410b4f2a98a1.tar.gz linux-0a1d52994d440e21def1c2174932410b4f2a98a1.tar.bz2 linux-0a1d52994d440e21def1c2174932410b4f2a98a1.zip | |
mm: enforce min addr even if capable() in expand_downwards()
security_mmap_addr() does a capability check with current_cred(), but
we can reach this code from contexts like a VFS write handler where
current_cred() must not be used.
This can be abused on systems without SMAP to make NULL pointer
dereferences exploitable again.
Fixes: 8869477a49c3 ("security: protect from stack expansion into low vm addresses")
Cc: stable@kernel.org
Signed-off-by: Jann Horn <jannh@google.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/mmap.c')
| -rw-r--r-- | mm/mmap.c | 7 |
1 files changed, 3 insertions, 4 deletions
diff --git a/mm/mmap.c b/mm/mmap.c index f901065c4c64..fc1809b1bed6 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -2426,12 +2426,11 @@ int expand_downwards(struct vm_area_struct *vma, { struct mm_struct *mm = vma->vm_mm; struct vm_area_struct *prev; - int error; + int error = 0; address &= PAGE_MASK; - error = security_mmap_addr(address); - if (error) - return error; + if (address < mmap_min_addr) + return -EPERM; /* Enforce stack_guard_gap */ prev = vma->vm_prev; |