Commit c4ea95d7 authored Dec 02, 2014 by Daniel Forrest Committed by Linus Torvalds Dec 03, 2014

mm: fix anon_vma_clone() error treatment



Andrew Morton noticed that the error return from anon_vma_clone() was
being dropped and replaced with -ENOMEM (which is not itself a bug
because the only error return value from anon_vma_clone() is -ENOMEM).

I did an audit of callers of anon_vma_clone() and discovered an actual
bug where the error return was being lost.  In __split_vma(), between
Linux 3.11 and 3.12 the code was changed so the err variable is used
before the call to anon_vma_clone() and the default initial value of
-ENOMEM is overwritten.  So a failure of anon_vma_clone() will return
success since err at this point is now zero.

Below is a patch which fixes this bug and also propagates the error
return value from anon_vma_clone() in all cases.

Fixes: ef0855d3 ("mm: mempolicy: turn vma_set_policy() into vma_dup_policy()")
Signed-off-by: Daniel Forrest <dan.forrest@ssec.wisc.edu>
Reviewed-by: Michal Hocko <mhocko@suse.cz>
Cc: Konstantin Khlebnikov <koct9i@gmail.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Tim Hartrick <tim@edgecast.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Michel Lespinasse <walken@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: <stable@vger.kernel.org>	[3.12+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent 2022b4d1

mm/mmap.c

+7 −3

Original line number	Diff line number	Diff line
		@@ -776,8 +776,11 @@ again: remove_next = 1 + (end > next->vm_end);
		* shrinking vma had, to cover any anon pages imported.
		*/
		if (exporter && exporter->anon_vma && !importer->anon_vma) {
		if (anon_vma_clone(importer, exporter))
		return -ENOMEM;
		int error;

		error = anon_vma_clone(importer, exporter);
		if (error)
		return error;
		importer->anon_vma = exporter->anon_vma;
		}
		}
		@@ -2469,7 +2472,8 @@ static int __split_vma(struct mm_struct mm, struct vm_area_struct vma,
		if (err)
		goto out_free_vma;

		if (anon_vma_clone(new, vma))
		err = anon_vma_clone(new, vma);
		if (err)
		goto out_free_mpol;

		if (new->vm_file)

mm/rmap.c

+4 −2

Original line number	Diff line number	Diff line
		@@ -274,6 +274,7 @@ int anon_vma_fork(struct vm_area_struct vma, struct vm_area_struct pvma)
		{
		struct anon_vma_chain *avc;
		struct anon_vma *anon_vma;
		int error;

		/* Don't bother if the parent process has no anon_vma here. */
		if (!pvma->anon_vma)
		@@ -283,8 +284,9 @@ int anon_vma_fork(struct vm_area_struct vma, struct vm_area_struct pvma)
		* First, attach the new VMA to the parent VMA's anon_vmas,
		* so rmap can find non-COWed pages in child processes.
		*/
		if (anon_vma_clone(vma, pvma))
		return -ENOMEM;
		error = anon_vma_clone(vma, pvma);
		if (error)
		return error;

		/* Then add our own anon_vma. */
		anon_vma = anon_vma_alloc();

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