[PATCH 20/21] btrfs: scrub: Set bbio to NULL before calling btrfs_map_block

David Sterba
2016-06-03T15:43:31Z

From: Zhao Lei <zhaolei@cn.fujitsu.com>

commit f1fee6534dcfbf468a159789aa202db2bce8c200 upstream.

We usually call btrfs_put_bbio() when btrfs_map_block() failed,
btrfs_put_bbio() works right whether bbio is a valid value, or NULL.

But there is a exception, in some case, btrfs_map_block() will return
fail without touching *bbio(keeping its original value), and if bbio
was not initialized yet, invalid memory accessing will happened.

Above case is in scrub_missing_raid56_pages(), and similar case in
scrub_raid56_parity().

Signed-off-by: Zhao Lei <zhaolei@cn.fujitsu.com>
Signed-off-by: David Sterba <dsterba@suse.com>
---
fs/btrfs/scrub.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/fs/btrfs/scrub.c b/fs/btrfs/scrub.c
index ee046f6fffe0..2b7986e9df03 100644
--- a/fs/btrfs/scrub.c
+++ b/fs/btrfs/scrub.c
@@ -2179,7 +2179,7 @@ static void scrub_missing_raid56_pages(struct scrub_block *sblock)
struct btrfs_fs_info *fs_info = sctx->dev_root->fs_info;
u64 length = sblock->page_count * PAGE_SIZE;
u64 logical = sblock->pagev[0]->logical;
- struct btrfs_bio *bbio;
+ struct btrfs_bio *bbio = NULL;
struct bio *bio;
struct btrfs_raid_bio *rbio;
int ret;
@@ -2980,6 +2980,7 @@ static noinline_for_stack int scrub_raid56_parity(struct scrub_ctx *sctx,
extent_len);

mapped_length = extent_len;
+ bbio = NULL;
ret = btrfs_map_block(fs_info, READ, extent_logical,
&mapped_length, &bbio, 0);
if (!ret) {
--
2.7.1