[PATCH 4.4 027/114] radix-tree: fix radix_tree_iter_retry() for tagged iterators.

Greg Kroah-Hartman
2018-11-08T21:50:42Z

[ 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@virtuozzo.com
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;
}

--
2.17.1