[PATCH][ext4-next] ext4: fix null pointer dereference on sbi

[Colin King]

From: Colin Ian King <colin.k...@canonical.com>

In the case of a kzalloc failure when allocating sbi we end up
with a null pointer dereference on sbi when assigning sbi->s_daxdev.
Fix this by moving the assignment of sbi->s_daxdev to after the
null pointer check of sbi.

Detected by CoverityScan CID#1455379 ("Dereference before null check")

Fixes: 5e405595e5bf ("ext4: perform dax_device lookup at mount")
Signed-off-by: Colin Ian King <colin.k...@canonical.com>
---
 fs/ext4/super.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 0e63fcd12c5b..71b9a667e1bc 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -3422,10 +3422,10 @@ static int ext4_fill_super(struct super_block *sb, void 
*data, int silent)
        unsigned int journal_ioprio = DEFAULT_JOURNAL_IOPRIO;
        ext4_group_t first_not_zeroed;
 
-       sbi->s_daxdev = dax_dev;
        if ((data && !orig_data) || !sbi)
                goto out_free_base;
 
+       sbi->s_daxdev = dax_dev;
        sbi->s_blockgroup_lock =
                kzalloc(sizeof(struct blockgroup_lock), GFP_KERNEL);
        if (!sbi->s_blockgroup_lock)
-- 
2.14.1