| From | Paul Gortmaker <> | Subject | [34-longterm 034/196] mm: avoid wrapping vm_pgoff in mremap() | Date | Mon, 12 Mar 2012 20:12:42 -0400 |
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From: Linus Torvalds <torvalds@linux-foundation.org>
------------------- This is a commit scheduled for the next v2.6.34 longterm release. If you see a problem with using this for longterm, please comment. -------------------
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: Paul Gortmaker <paul.gortmaker@windriver.com> --- mm/mremap.c | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-)
diff --git a/mm/mremap.c b/mm/mremap.c index 10d5f62..97de5ae 100644 --- a/mm/mremap.c +++ b/mm/mremap.c @@ -274,9 +274,16 @@ 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) { -- 1.7.9.3
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