The patch titled Subject: mempolicy: fix a memory corruption by refcount imbalance in alloc_pages_vma() has been removed from the -mm tree. Its filename was mempolicy-fix-a-memory-corruption-by-refcount-imbalance-in-alloc_pages_vma.patch This patch was dropped because it was merged into mainline or a subsystem tree ------------------------------------------------------ From: Mel Gorman <mgorman@xxxxxxx> Subject: mempolicy: fix a memory corruption by refcount imbalance in alloc_pages_vma() cc9a6c87 ("cpuset: mm: reduce large amounts of memory barrier related damage v3") introduced a potential memory corruption. shmem_alloc_page() uses a pseudo vma and it has one significant unique combination, vma->vm_ops=NULL and vma->policy->flags & MPOL_F_SHARED. get_vma_policy() does NOT increase a policy ref when vma->vm_ops=NULL and mpol_cond_put() DOES decrease a policy ref when a policy has MPOL_F_SHARED. Therefore, when a cpuset update race occurs, alloc_pages_vma() falls in 'goto retry_cpuset' path, decrements the reference count and frees the policy prematurely. Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx> Signed-off-by: Mel Gorman <mgorman@xxxxxxx> Reviewed-by: Christoph Lameter <cl@xxxxxxxxx> Cc: Josh Boyer <jwboyer@xxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/mempolicy.c | 12 +++++++++++- 1 file changed, 11 insertions(+), 1 deletion(-) diff -puN mm/mempolicy.c~mempolicy-fix-a-memory-corruption-by-refcount-imbalance-in-alloc_pages_vma mm/mempolicy.c --- a/mm/mempolicy.c~mempolicy-fix-a-memory-corruption-by-refcount-imbalance-in-alloc_pages_vma +++ a/mm/mempolicy.c @@ -1552,8 +1552,18 @@ struct mempolicy *get_vma_policy(struct addr); if (vpol) pol = vpol; - } else if (vma->vm_policy) + } else if (vma->vm_policy) { pol = vma->vm_policy; + + /* + * shmem_alloc_page() passes MPOL_F_SHARED policy with + * a pseudo vma whose vma->vm_ops=NULL. Take a reference + * count on these policies which will be dropped by + * mpol_cond_put() later + */ + if (mpol_needs_cond_ref(pol)) + mpol_get(pol); + } } if (!pol) pol = &default_policy; _ Patches currently in -mm which might be from mgorman@xxxxxxx are origin.patch -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html