The patch titled
Subject: tmpfs: fix shared mempolicy leak
has been added to the -mm tree. Its filename is
tmpfs-fix-shared-mempolicy-leak.patch
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------------------------------------------------------
From: Mel Gorman <mgorman@xxxxxxx>
Subject: tmpfs: fix shared mempolicy leak
This fixes a regression in 3.7-rc, which has since gone into stable.
Commit 00442ad04a5e ("mempolicy: fix a memory corruption by refcount
imbalance in alloc_pages_vma()") changed get_vma_policy() to raise the
refcount on a shmem shared mempolicy; whereas shmem_alloc_page() went on
expecting alloc_page_vma() to drop the refcount it had acquired. This
deserves a rework: but for now fix the leak in shmem_alloc_page().
Hugh: shmem_swapin() did not need a fix, but surely it's clearer to use
the same refcounting there as in shmem_alloc_page(), delete its onstack
mempolicy, and the strange mpol_cond_copy() and __mpol_cond_copy() - those
were invented to let swapin_readahead() make an unknown number of calls to
alloc_pages_vma() with one mempolicy; but since 00442ad04a5e,
alloc_pages_vma() has kept refcount in balance, so now no problem.
Reported-and-tested-by: Tommi Rantala <tt.rantala@xxxxxxxxx>
Signed-off-by: Mel Gorman <mgorman@xxxxxxx>
Signed-off-by: Hugh Dickins <hughd@xxxxxxxxxx>
Tested-by: Tommi Rantala <tt.rantala@xxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/mempolicy.h | 16 ----------------
mm/mempolicy.c | 22 ----------------------
mm/shmem.c | 26 ++++++++++++++++----------
3 files changed, 16 insertions(+), 48 deletions(-)
diff -puN include/linux/mempolicy.h~tmpfs-fix-shared-mempolicy-leak include/linux/mempolicy.h
--- a/include/linux/mempolicy.h~tmpfs-fix-shared-mempolicy-leak
+++ a/include/linux/mempolicy.h
@@ -82,16 +82,6 @@ static inline void mpol_cond_put(struct
__mpol_put(pol);
}
-extern struct mempolicy *__mpol_cond_copy(struct mempolicy *tompol,
- struct mempolicy *frompol);
-static inline struct mempolicy *mpol_cond_copy(struct mempolicy *tompol,
- struct mempolicy *frompol)
-{
- if (!frompol)
- return frompol;
- return __mpol_cond_copy(tompol, frompol);
-}
-
extern struct mempolicy *__mpol_dup(struct mempolicy *pol);
static inline struct mempolicy *mpol_dup(struct mempolicy *pol)
{
@@ -215,12 +205,6 @@ static inline void mpol_cond_put(struct
{
}
-static inline struct mempolicy *mpol_cond_copy(struct mempolicy *to,
- struct mempolicy *from)
-{
- return from;
-}
-
static inline void mpol_get(struct mempolicy *pol)
{
}
diff -puN mm/mempolicy.c~tmpfs-fix-shared-mempolicy-leak mm/mempolicy.c
--- a/mm/mempolicy.c~tmpfs-fix-shared-mempolicy-leak
+++ a/mm/mempolicy.c
@@ -2037,28 +2037,6 @@ struct mempolicy *__mpol_dup(struct memp
return new;
}
-/*
- * If *frompol needs [has] an extra ref, copy *frompol to *tompol ,
- * eliminate the * MPOL_F_* flags that require conditional ref and
- * [NOTE!!!] drop the extra ref. Not safe to reference *frompol directly
- * after return. Use the returned value.
- *
- * Allows use of a mempolicy for, e.g., multiple allocations with a single
- * policy lookup, even if the policy needs/has extra ref on lookup.
- * shmem_readahead needs this.
- */
-struct mempolicy *__mpol_cond_copy(struct mempolicy *tompol,
- struct mempolicy *frompol)
-{
- if (!mpol_needs_cond_ref(frompol))
- return frompol;
-
- *tompol = *frompol;
- tompol->flags &= ~MPOL_F_SHARED; /* copy doesn't need unref */
- __mpol_put(frompol);
- return tompol;
-}
-
/* Slow path of a mempolicy comparison */
bool __mpol_equal(struct mempolicy *a, struct mempolicy *b)
{
diff -puN mm/shmem.c~tmpfs-fix-shared-mempolicy-leak mm/shmem.c
--- a/mm/shmem.c~tmpfs-fix-shared-mempolicy-leak
+++ a/mm/shmem.c
@@ -910,25 +910,29 @@ static struct mempolicy *shmem_get_sbmpo
static struct page *shmem_swapin(swp_entry_t swap, gfp_t gfp,
struct shmem_inode_info *info, pgoff_t index)
{
- struct mempolicy mpol, *spol;
struct vm_area_struct pvma;
-
- spol = mpol_cond_copy(&mpol,
- mpol_shared_policy_lookup(&info->policy, index));
+ struct page *page;
/* Create a pseudo vma that just contains the policy */
pvma.vm_start = 0;
/* Bias interleave by inode number to distribute better across nodes */
pvma.vm_pgoff = index + info->vfs_inode.i_ino;
pvma.vm_ops = NULL;
- pvma.vm_policy = spol;
- return swapin_readahead(swap, gfp, &pvma, 0);
+ pvma.vm_policy = mpol_shared_policy_lookup(&info->policy, index);
+
+ page = swapin_readahead(swap, gfp, &pvma, 0);
+
+ /* Drop reference taken by mpol_shared_policy_lookup() */
+ mpol_cond_put(pvma.vm_policy);
+
+ return page;
}
static struct page *shmem_alloc_page(gfp_t gfp,
struct shmem_inode_info *info, pgoff_t index)
{
struct vm_area_struct pvma;
+ struct page *page;
/* Create a pseudo vma that just contains the policy */
pvma.vm_start = 0;
@@ -937,10 +941,12 @@ static struct page *shmem_alloc_page(gfp
pvma.vm_ops = NULL;
pvma.vm_policy = mpol_shared_policy_lookup(&info->policy, index);
- /*
- * alloc_page_vma() will drop the shared policy reference
- */
- return alloc_page_vma(gfp, &pvma, 0);
+ page = alloc_page_vma(gfp, &pvma, 0);
+
+ /* Drop reference taken by mpol_shared_policy_lookup() */
+ mpol_cond_put(pvma.vm_policy);
+
+ return page;
}
#else /* !CONFIG_NUMA */
#ifdef CONFIG_TMPFS
_
Patches currently in -mm which might be from mgorman@xxxxxxx are
tmpfs-fix-shared-mempolicy-leak.patch
linux-next.patch
memory_hotplug-fix-possible-incorrect-node_states.patch
slub-hotplug-ignore-unrelated-nodes-hot-adding-and-hot-removing.patch
mm-add-comment-on-storage-key-dirty-bit-semantics.patch
mm-refactor-reinsert-of-swap_info-in-sys_swapoff.patch
mm-do-not-call-frontswap_init-during-swapoff.patch
mm-memmap_init_zone-performance-improvement.patch
mm-allocate-kernel-pages-to-the-right-memcg.patch
mm-memory-hotplug-dynamic-configure-movable-memory-and-portion-memory.patch
memory_hotplug-handle-empty-zone-when-online_movable-online_kernel.patch
memory_hotplug-ensure-every-online-node-has-normal-memory.patch
mm-compaction-fix-compiler-warning.patch
mm-add-a-reminder-comment-for-__gfp_bits_shift.patch
numa-add-config_movable_node-for-movable-dedicated-node.patch
numa-add-config_movable_node-for-movable-dedicated-node-fix.patch
memory_hotplug-allow-online-offline-memory-to-result-movable-node.patch
mm-introduce-new-field-managed_pages-to-struct-zone.patch
mm-provide-more-accurate-estimation-of-pages-occupied-by-memmap.patch
mm-provide-more-accurate-estimation-of-pages-occupied-by-memmap-fix.patch
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