[PATCH] nvmet-tcp: fix NULL pointer dereference in nvmet_execute_identify_nslist()

nvmet_execute_identify_nslist() handles the I/O Command Set Active
Namespace ID List (CNS 07h) with match_css set. The per-namespace
filter in the iteration loop tests req->ns->csi, but req->ns is NULL
for this command: nvmet_req_init() clears req->ns for every request,
and CNS 07h uses the NSID field only as a starting filter (min_nsid),
so no namespace is ever looked up. The intended value is the loop
variable ns->csi.

A remote host that sends an Identify command with CNS 07h to a
subsystem with at least one enabled namespace dereferences the NULL
req->ns (at offsetof(struct nvmet_ns, csi)) and crashes the target.
Use the loop variable ns instead.

Fixes: 61c9967cd634 ("nvmet: implement active command set ns list")
Assisted-by: Claude:claude-opus-4-8
Signed-off-by: Shivam Kumar <[email protected]>
Cc: [email protected]
---
 drivers/nvme/target/admin-cmd.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/nvme/target/admin-cmd.c b/drivers/nvme/target/admin-cmd.c
index 01b799e92ae6..ab6a0a98dd5d 100644
--- a/drivers/nvme/target/admin-cmd.c
+++ b/drivers/nvme/target/admin-cmd.c
@@ -958,7 +958,7 @@ static void nvmet_execute_identify_nslist(struct nvmet_req *req, bool match_css)
 	nvmet_for_each_enabled_ns(&ctrl->subsys->namespaces, idx, ns) {
 		if (ns->nsid <= min_nsid)
 			continue;
-		if (match_css && req->ns->csi != req->cmd->identify.csi)
+		if (match_css && ns->csi != req->cmd->identify.csi)
 			continue;
 		list[i++] = cpu_to_le32(ns->nsid);
 		if (i == buf_size / sizeof(__le32))
-- 
2.53.0