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authorLinus Torvalds <torvalds@linux-foundation.org>2011-04-07 07:35:50 -0700
committerGreg Kroah-Hartman <gregkh@suse.de>2011-04-14 16:53:30 -0700
commitd7c75177f0cae6bb0ec22d2180076f46c5d4d362 (patch)
treee52c22cb5f381b9c783f97f7cf49526d7b75b57f
parent8975a50e80906e43575b419f7849d251311a2067 (diff)
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mm: avoid wrapping vm_pgoff in mremap()
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>
-rw-r--r--mm/mremap.c11
1 files changed, 9 insertions, 2 deletions
diff --git a/mm/mremap.c b/mm/mremap.c
index 166b824c2066..3e98d79f5589 100644
--- a/mm/mremap.c
+++ b/mm/mremap.c
@@ -275,9 +275,16 @@ 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) {