diff options
| author | Jann Horn <jannh@google.com> | 2019-02-27 23:29:52 +0300 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2019-03-23 10:18:54 +0300 |
| commit | f290a73f3e919c4d5482632284ccb0aa17f7380c (patch) | |
| tree | e3d9249b51f5f2d0ac0efc015f3c8cbe67a3ed15 | |
| parent | c3ccbb431fe130d63a131739d143e055e10556e2 (diff) | |
| download | linux-f290a73f3e919c4d5482632284ccb0aa17f7380c.tar.xz | |
mm: enforce min addr even if capable() in expand_downwards()
commit 0a1d52994d440e21def1c2174932410b4f2a98a1 upstream.
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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -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 698d103c904c..738c926fb1ec 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -2292,12 +2292,11 @@ int expand_downwards(struct vm_area_struct *vma, { struct vm_area_struct *prev; unsigned long gap_addr; - 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 */ gap_addr = address - stack_guard_gap; |