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

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

From: Dan Robertson <[email protected]>

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")
CC: [email protected] # 3.0+
Reviewed-by: Nikolay Borisov <[email protected]>
Signed-off-by: Dan Robertson <[email protected]>
Reviewed-by: David Sterba <[email protected]>
Signed-off-by: David Sterba <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>

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

--- a/fs/btrfs/scrub.c
+++ b/fs/btrfs/scrub.c
@@ -584,6 +584,7 @@ static noinline_for_stack struct scrub_c
        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_c
        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);


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