linux-kernel - [PATCH 4.5 127/128] btrfs: scrub: Set bbio to NULL before calling btrfs_map

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Date:	Sun,  5 Jun 2016 15:24:42 -0700
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org, Zhao Lei <zhaolei@...fujitsu.com>,
	David Sterba <dsterba@...e.com>
Subject: [PATCH 4.5 127/128] btrfs: scrub: Set bbio to NULL before calling btrfs_map_block

4.5-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Zhao Lei <zhaolei@...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@...fujitsu.com>
Signed-off-by: David Sterba <dsterba@...e.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 fs/btrfs/scrub.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/fs/btrfs/scrub.c
+++ b/fs/btrfs/scrub.c
@@ -2179,7 +2179,7 @@ static void scrub_missing_raid56_pages(s
 	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 @@ again:
 						       extent_len);
 
 			mapped_length = extent_len;
+			bbio = NULL;
 			ret = btrfs_map_block(fs_info, READ, extent_logical,
 					      &mapped_length, &bbio, 0);
 			if (!ret) {