4.4-stable review patch. If anyone has any objections, please let me know.
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[ Upstream commit 3cb9185c67304b2a7ea9be73e7d13df6fb2793a1 ]
radix_tree_iter_retry() resets slot to NULL, but it doesn't reset tags. Then NULL slot and non-zero iter.tags passed to radix_tree_next_slot() leading to crash:
RIP: radix_tree_next_slot include/linux/radix-tree.h:473 find_get_pages_tag+0x334/0x930 mm/filemap.c:1452 .... Call Trace: pagevec_lookup_tag+0x3a/0x80 mm/swap.c:960 mpage_prepare_extent_to_map+0x321/0xa90 fs/ext4/inode.c:2516 ext4_writepages+0x10be/0x2b20 fs/ext4/inode.c:2736 do_writepages+0x97/0x100 mm/page-writeback.c:2364 __filemap_fdatawrite_range+0x248/0x2e0 mm/filemap.c:300 filemap_write_and_wait_range+0x121/0x1b0 mm/filemap.c:490 ext4_sync_file+0x34d/0xdb0 fs/ext4/fsync.c:115 vfs_fsync_range+0x10a/0x250 fs/sync.c:195 vfs_fsync fs/sync.c:209 do_fsync+0x42/0x70 fs/sync.c:219 SYSC_fdatasync fs/sync.c:232 SyS_fdatasync+0x19/0x20 fs/sync.c:230 entry_SYSCALL_64_fastpath+0x23/0xc1 arch/x86/entry/entry_64.S:207
We must reset iterator's tags to bail out from radix_tree_next_slot() and go to the slow-path in radix_tree_next_chunk().
Fixes: 46437f9a554f ("radix-tree: fix race in gang lookup") Link: http://lkml.kernel.org/r/1468495196-10604-1-git-send-email-aryabinin@virtuoz... Signed-off-by: Andrey Ryabinin aryabinin@virtuozzo.com Reported-by: Dmitry Vyukov dvyukov@google.com Acked-by: Konstantin Khlebnikov koct9i@gmail.com Cc: Matthew Wilcox willy@linux.intel.com Cc: Hugh Dickins hughd@google.com Cc: Ross Zwisler ross.zwisler@linux.intel.com Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Linus Torvalds torvalds@linux-foundation.org Signed-off-by: Sasha Levin sashal@kernel.org --- include/linux/radix-tree.h | 1 + 1 file changed, 1 insertion(+)
diff --git a/include/linux/radix-tree.h b/include/linux/radix-tree.h index 5d5174b59802..673dee29a9b9 100644 --- a/include/linux/radix-tree.h +++ b/include/linux/radix-tree.h @@ -382,6 +382,7 @@ static inline __must_check void **radix_tree_iter_retry(struct radix_tree_iter *iter) { iter->next_index = iter->index; + iter->tags = 0; return NULL; }