Commit 2897b4d2 authored Dec 12, 2012 by Joonsoo Kim Committed by Linus Torvalds Dec 12, 2012

mm: WARN_ON_ONCE if f_op->mmap() change vma's start address

During reviewing the source code, I found a comment which mention that
after f_op->mmap(), vma's start address can be changed. I didn't verify
that it is really possible, because there are so many f_op->mmap()
implementation. But if there are some mmap() which change vma's start
address, it is possible error situation, because we already prepare prev
vma, rb_link and rb_parent and these are related to original address.

So add WARN_ON_ONCE for finding that this situtation really happens.

Signed-off-by: Joonsoo Kim <js1304@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent 44e33e8f

mm/mmap.c

+4 −0

Original line number	Diff line number	Diff line
		@@ -1488,7 +1488,11 @@ munmap_back:
		*
		* Answer: Yes, several device drivers can do it in their
		* f_op->mmap method. -DaveM
		* Bug: If addr is changed, prev, rb_link, rb_parent should
		* be updated for vma_link()
		*/
		WARN_ON_ONCE(addr != vma->vm_start);

		addr = vma->vm_start;
		pgoff = vma->vm_pgoff;
		vm_flags = vma->vm_flags;

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