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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>
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1 changed files with 9 additions and 2 deletions
11
mm/mremap.c
11
mm/mremap.c
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@ -277,9 +277,16 @@ static struct vm_area_struct *vma_to_resize(unsigned long addr,
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if (old_len > vma->vm_end - addr)
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goto Efault;
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if (vma->vm_flags & (VM_DONTEXPAND | VM_PFNMAP)) {
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if (new_len > old_len)
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/* Need to be careful about a growing mapping */
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if (new_len > old_len) {
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unsigned long pgoff;
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if (vma->vm_flags & (VM_DONTEXPAND | VM_PFNMAP))
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goto Efault;
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pgoff = (addr - vma->vm_start) >> PAGE_SHIFT;
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pgoff += vma->vm_pgoff;
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if (pgoff + (new_len >> PAGE_SHIFT) < pgoff)
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goto Einval;
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}
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if (vma->vm_flags & VM_LOCKED) {
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