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: ef0855d334e1 ("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>
* 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;
}
}
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)
{
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)
* 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();