The patch titled
Subject: tmpfs: fix shmem_getpage_gfp() VM_BUG_ON
has been removed from the -mm tree. Its filename was
tmpfs-fix-shmem_getpage_gfp-vm_bug_on.patch
This patch was dropped because it was merged into mainline or a subsystem tree
------------------------------------------------------
From: Hugh Dickins <hughd@xxxxxxxxxx>
Subject: tmpfs: fix shmem_getpage_gfp() VM_BUG_ON
Fuzzing with trinity hit the "impossible" VM_BUG_ON(error) (which Fedora
has converted to WARNING) in shmem_getpage_gfp():
WARNING: at mm/shmem.c:1151 shmem_getpage_gfp+0xa5c/0xa70()
Pid: 29795, comm: trinity-child4 Not tainted 3.7.0-rc2+ #49
Call Trace:
[<ffffffff8107100f>] warn_slowpath_common+0x7f/0xc0
[<ffffffff8107106a>] warn_slowpath_null+0x1a/0x20
[<ffffffff811903fc>] shmem_getpage_gfp+0xa5c/0xa70
[<ffffffff81190e4f>] shmem_fault+0x4f/0xa0
[<ffffffff8119f391>] __do_fault+0x71/0x5c0
[<ffffffff811a2767>] handle_pte_fault+0x97/0xae0
[<ffffffff811a4a39>] handle_mm_fault+0x289/0x350
[<ffffffff816d091e>] __do_page_fault+0x18e/0x530
[<ffffffff816d0ceb>] do_page_fault+0x2b/0x50
[<ffffffff816cd3b8>] page_fault+0x28/0x30
[<ffffffff816d5688>] tracesys+0xe1/0xe6
Thanks to Johannes for pointing to truncation: free_swap_and_cache() only
does a trylock on the page, so the page lock we've held since before
confirming swap is not enough to protect against truncation.
What cleanup is needed in this case? Just delete_from_swap_cache(), which
takes care of the memcg uncharge.
Signed-off-by: Hugh Dickins <hughd@xxxxxxxxxx>
Reported-by: Dave Jones <davej@xxxxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/shmem.c | 16 ++++++++++++++--
1 file changed, 14 insertions(+), 2 deletions(-)
diff -puN mm/shmem.c~tmpfs-fix-shmem_getpage_gfp-vm_bug_on mm/shmem.c
--- a/mm/shmem.c~tmpfs-fix-shmem_getpage_gfp-vm_bug_on
+++ a/mm/shmem.c
@@ -1145,8 +1145,20 @@ repeat:
if (!error) {
error = shmem_add_to_page_cache(page, mapping, index,
gfp, swp_to_radix_entry(swap));
- /* We already confirmed swap, and make no allocation */
- VM_BUG_ON(error);
+ /*
+ * We already confirmed swap under page lock, and make
+ * no memory allocation here, so usually no possibility
+ * of error; but free_swap_and_cache() only trylocks a
+ * page, so it is just possible that the entry has been
+ * truncated or holepunched since swap was confirmed.
+ * shmem_undo_range() will have done some of the
+ * unaccounting, now delete_from_swap_cache() will do
+ * the rest (including mem_cgroup_uncharge_swapcache).
+ * Reset swap.val? No, leave it so "failed" goes back to
+ * "repeat": reading a hole and writing should succeed.
+ */
+ if (error)
+ delete_from_swap_cache(page);
}
if (error)
goto failed;
_
Patches currently in -mm which might be from hughd@xxxxxxxxxx are
linux-next.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-augment-vma-rbtree-with-rb_subtree_gap.patch
mm-augment-vma-rbtree-with-rb_subtree_gap-ensure-safe-rb_subtree_gap-update-when-inserting-new-vma.patch
mm-augment-vma-rbtree-with-rb_subtree_gap-ensure-safe-rb_subtree_gap-update-when-removing-vma.patch
mm-augment-vma-rbtree-with-rb_subtree_gap--debug-code-to-verify-rb_subtree_gap-updates-are-safe.patch
mm-check-rb_subtree_gap-correctness.patch
mm-check-rb_subtree_gap-correctness-fix.patch
mm-rearrange-vm_area_struct-for-fewer-cache-misses.patch
mm-vm_unmapped_area-lookup-function.patch
mm-use-vm_unmapped_area-on-x86_64-architecture.patch
mm-fix-cache-coloring-on-x86_64-architecture.patch
mm-use-vm_unmapped_area-in-hugetlbfs.patch
mm-use-vm_unmapped_area-in-hugetlbfs-on-i386-architecture.patch
mm-use-vm_unmapped_area-in-hugetlbfs-on-i386-architecture-fix.patch
mm-use-vm_unmapped_area-on-mips-architecture.patch
mm-use-vm_unmapped_area-on-mips-architecture-fix.patch
mm-use-vm_unmapped_area-on-arm-architecture.patch
mm-use-vm_unmapped_area-on-arm-architecture-fix.patch
mm-use-vm_unmapped_area-on-sh-architecture.patch
mm-use-vm_unmapped_area-on-sh-architecture-fix.patch
mm-use-vm_unmapped_area-on-sparc32-architecture.patch
mm-use-vm_unmapped_area-in-hugetlbfs-on-tile-architecture.patch
mm-use-vm_unmapped_area-on-sparc64-architecture.patch
mm-use-vm_unmapped_area-on-sparc64-architecture-fix.patch
mm-use-vm_unmapped_area-in-hugetlbfs-on-sparc64-architecture.patch
swap-add-a-simple-detector-for-inappropriate-swapin-readahead.patch
swap-add-a-simple-detector-for-inappropriate-swapin-readahead-fix.patch
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