From: Daniel Forrest <[email protected]>
Subject: 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: ef0855d334e1 ("mm: mempolicy: turn vma_set_policy() into
vma_dup_policy()")
Signed-off-by: Daniel Forrest <[email protected]>
Reviewed-by: Michal Hocko <[email protected]>
Cc: Konstantin Khlebnikov <[email protected]>
Cc: Andrea Arcangeli <[email protected]>
Cc: Rik van Riel <[email protected]>
Cc: Tim Hartrick <[email protected]>
Cc: Hugh Dickins <[email protected]>
Cc: Michel Lespinasse <[email protected]>
Cc: Vlastimil Babka <[email protected]>
Cc: <[email protected]> [3.12+]
Signed-off-by: Andrew Morton <[email protected]>
---
mm/mmap.c | 10 +++++++---
mm/rmap.c | 6 ++++--
2 files changed, 11 insertions(+), 5 deletions(-)
diff -puN mm/mmap.c~mm-fix-anon_vma_clone-error-treatment mm/mmap.c
--- a/mm/mmap.c~mm-fix-anon_vma_clone-error-treatment
+++ a/mm/mmap.c
@@ -776,8 +776,11 @@ again: remove_next = 1 + (end > next->
* 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
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)
diff -puN mm/rmap.c~mm-fix-anon_vma_clone-error-treatment mm/rmap.c
--- a/mm/rmap.c~mm-fix-anon_vma_clone-error-treatment
+++ a/mm/rmap.c
@@ -274,6 +274,7 @@ int anon_vma_fork(struct vm_area_struct
{
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
* 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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