[PATCH] nvme: host: core: fix NULL pointer dereference in nvme_pr_command

[Gustavo A. R. Silva]

_head_ pointer is being dereferenced when it is NULL.

Fix this by moving the code that dereferences such pointer after it has
been properly initialized in function nvme_get_ns_from_disk.

Addresses-Coverity-ID: 1461344
Fixes: 32acab3181c7 ("nvme: implement multipath access to nvme subsystems")
Signed-off-by: Gustavo A. R. Silva <garsi...@embeddedor.com>
---
 drivers/nvme/host/core.c | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
index 25da74d..9b9c324 100644
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -1452,16 +1452,16 @@ static int nvme_pr_command(struct block_device *bdev, 
u32 cdw10,
        put_unaligned_le64(key, &data[0]);
        put_unaligned_le64(sa_key, &data[8]);
 
-       memset(&c, 0, sizeof(c));
-       c.common.opcode = op;
-       c.common.nsid = cpu_to_le32(head->ns_id);
-       c.common.cdw10[0] = cpu_to_le32(cdw10);
-
        ns = nvme_get_ns_from_disk(bdev->bd_disk, &head, &srcu_idx);
-       if (unlikely(!ns))
+       if (unlikely(!ns)) {
                ret = -EWOULDBLOCK;
-       else
+       } else {
+               memset(&c, 0, sizeof(c));
+               c.common.opcode = op;
+               c.common.nsid = cpu_to_le32(head->ns_id);
+               c.common.cdw10[0] = cpu_to_le32(cdw10);
                ret = nvme_submit_sync_cmd(ns->queue, &c, data, 16);
+       }
        nvme_put_ns_from_disk(head, srcu_idx);
        return ret;
 }
-- 
2.7.4