From: Linus Torvalds Date: Thu, 7 Apr 2011 14:35:50 +0000 (-0700) Subject: mm: avoid wrapping vm_pgoff in mremap() X-Git-Tag: firefly_0821_release~10186^2~242 X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=d7c75177f0cae6bb0ec22d2180076f46c5d4d362;p=firefly-linux-kernel-4.4.55.git 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 Acked-by: Hugh Dickins Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- 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) {