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| author | Linus Torvalds <torvalds@linux-foundation.org> | 2011-04-07 07:35:50 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2011-04-07 07:35:51 -0700 |
| commit | 982134ba62618c2d69fbbbd166d0a11ee3b7e3d8 (patch) | |
| tree | 32aae4719abbd338864ab6faf9e8ebbfc38b1600 /mm/mremap.c | |
| parent | 6221f222c0ebf1acdf7abcf927178f40e1a65e2a (diff) | |
| download | lwn-982134ba62618c2d69fbbbd166d0a11ee3b7e3d8.tar.gz lwn-982134ba62618c2d69fbbbd166d0a11ee3b7e3d8.zip | |
mm: avoid wrapping vm_pgoff in mremap()
The normal mmap paths all avoid creating a mapping where the pgoff
inside the mapping could wrap around due to overflow. However, an
expanding mremap() can take such a non-wrapping mapping and make it
bigger and cause a wrapping condition.
Noticed by Robert Swiecki when running a system call fuzzer, where it
caused a BUG_ON() due to terminally confusing the vma_prio_tree code. A
vma dumping patch by Hugh then pinpointed the crazy wrapped case.
Reported-and-tested-by: Robert Swiecki <robert@swiecki.net>
Acked-by: Hugh Dickins <hughd@google.com>
Cc: stable@kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/mremap.c')
| -rw-r--r-- | mm/mremap.c | 11 |
1 files changed, 9 insertions, 2 deletions
diff --git a/mm/mremap.c b/mm/mremap.c index 1de98d492ddc..a7c1f9f9b941 100644 --- a/mm/mremap.c +++ b/mm/mremap.c @@ -277,9 +277,16 @@ static struct vm_area_struct *vma_to_resize(unsigned long addr, if (old_len > vma->vm_end - addr) goto Efault; - if (vma->vm_flags & (VM_DONTEXPAND | VM_PFNMAP)) { - if (new_len > old_len) + /* Need to be careful about a growing mapping */ + if (new_len > old_len) { + unsigned long pgoff; + + if (vma->vm_flags & (VM_DONTEXPAND | VM_PFNMAP)) goto Efault; + pgoff = (addr - vma->vm_start) >> PAGE_SHIFT; + pgoff += vma->vm_pgoff; + if (pgoff + (new_len >> PAGE_SHIFT) < pgoff) + goto Einval; } if (vma->vm_flags & VM_LOCKED) { |