[PATCH 3.16 084/129] btrfs: init csum_list before possible free

[Ben Hutchings]

3.16.70-rc1 review patch.  If anyone has any objections, please let me know.

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

From: Dan Robertson <dan@xxxxxxxxxxxxxxx>

commit e49be14b8d80e23bb7c53d78c21717a474ade76b upstream.

The scrub_ctx csum_list member must be initialized before scrub_free_ctx
is called. If the csum_list is not initialized beforehand, the
list_empty call in scrub_free_csums will result in a null deref if the
allocation fails in the for loop.

Fixes: a2de733c78fa ("btrfs: scrub")
Reviewed-by: Nikolay Borisov <nborisov@xxxxxxxx>
Signed-off-by: Dan Robertson <dan@xxxxxxxxxxxxxxx>
Reviewed-by: David Sterba <dsterba@xxxxxxxx>
Signed-off-by: David Sterba <dsterba@xxxxxxxx>
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
 fs/btrfs/scrub.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/fs/btrfs/scrub.c
+++ b/fs/btrfs/scrub.c
@@ -417,6 +417,7 @@ struct scrub_ctx *scrub_setup_ctx(struct
 	sctx->pages_per_rd_bio = pages_per_rd_bio;
 	sctx->curr = -1;
 	sctx->dev_root = dev->dev_root;
+	INIT_LIST_HEAD(&sctx->csum_list);
 	for (i = 0; i < SCRUB_BIOS_PER_SCTX; ++i) {
 		struct scrub_bio *sbio;
 
@@ -444,7 +445,6 @@ struct scrub_ctx *scrub_setup_ctx(struct
 	atomic_set(&sctx->workers_pending, 0);
 	atomic_set(&sctx->cancel_req, 0);
 	sctx->csum_size = btrfs_super_csum_size(fs_info->super_copy);
-	INIT_LIST_HEAD(&sctx->csum_list);
 
 	spin_lock_init(&sctx->list_lock);
 	spin_lock_init(&sctx->stat_lock);