nvmet: fix space padding in serial number

[ Upstream commit c7399698 ]

Commit 42de82a8 previously attempted to fix this, and it did
correctly pad the MN and FR fields with spaces, but the SN field still
contains 0 bytes.  The current code fills out the first 16 bytes with
hex2bin, leaving the last 4 bytes zeroed.  Rather than adding a lot of
error-prone math to avoid overwriting SN twice, just set the whole thing
to spaces up front (it's only 20 bytes).

Fixes: 42de82a8 ("nvmet: don't report 0-bytes in serial number")
Signed-off-by: Daniel Verkamp <daniel.verkamp@intel.com>
Reviewed-by: Martin Wilck <mwilck@suse.com>
Signed-off-by: Keith Busch <keith.busch@intel.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <sashal@kernel.org>

drivers/nvme/target/admin-cmd.c

@@ -192,6 +192,7 @@ static void nvmet_execute_identify_ctrl(struct nvmet_req *req)
 	id->vid = 0;
 	id->ssvid = 0;
 
+	memset(id->sn, ' ', sizeof(id->sn));
 	bin2hex(id->sn, &ctrl->subsys->serial,
 		min(sizeof(ctrl->subsys->serial), sizeof(id->sn) / 2));
 	copy_and_pad(id->mn, sizeof(id->mn), model, sizeof(model) - 1);