btrfs: init csum_list before possible free

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")
CC: stable@vger.kernel.org # 3.0+
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Dan Robertson <dan@dlrobertson.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/fs/btrfs/scrub.c b/fs/btrfs/scrub.c
index 669bedfec4a9ab7be2fa3a1a5a82f924e8dd965b..a99588536c79e5fcbdbef4caf6a86852ea83205c 100644 (file)
--- a/fs/btrfs/scrub.c
+++ b/fs/btrfs/scrub.c
@@ -584,6 +584,7 @@ static noinline_for_stack struct scrub_ctx *scrub_setup_ctx(
        sctx->pages_per_rd_bio = SCRUB_PAGES_PER_RD_BIO;
        sctx->curr = -1;
        sctx->fs_info = fs_info;
+       INIT_LIST_HEAD(&sctx->csum_list);
        for (i = 0; i < SCRUB_BIOS_PER_SCTX; ++i) {
                struct scrub_bio *sbio;
 
@@ -608,7 +609,6 @@ static noinline_for_stack struct scrub_ctx *scrub_setup_ctx(
        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);