nvmet: nul-terminate the NQNs passed in the connect command

mainline inclusion
from mainline-v6.7-rc3
commit 1c22e0295a5eb571c27b53c7371f95699ef705ff
category: bugfix
bugzilla: https://gitee.com/src-openeuler/kernel/issues/I8H4UJ
CVE: CVE-2023-6121

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=1c22e0295a5eb571c27b53c7371f95699ef705ff



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The host and subsystem NQNs are passed in the connect command payload and
interpreted as nul-terminated strings.  Ensure they actually are
nul-terminated before using them.

Fixes: a07b4970 "nvmet: add a generic NVMe target")
Reported-by: Alon Zahavi <zahavi.alon@gmail.com>
Reviewed-by: Chaitanya Kulkarni <kch@nvidia.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Keith Busch <kbusch@kernel.org>
Signed-off-by: Cheng Yu <serein.chengyu@huawei.com>