Messages in this thread Patch in this message | | | Date | Wed, 13 Apr 2011 09:09:55 -0700 | From | Greg KH <> | Subject | [32/71] mm: avoid wrapping vm_pgoff in mremap() |
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2.6.33-longterm review patch. If anyone has any objections, please let us know.
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From: Linus Torvalds <torvalds@linux-foundation.org>
commit 982134ba62618c2d69fbbbd166d0a11ee3b7e3d8 upstream.
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> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
--- mm/mremap.c | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-)
--- a/mm/mremap.c +++ b/mm/mremap.c @@ -275,9 +275,16 @@ static struct vm_area_struct *vma_to_res 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) {
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