[RFC v1 1/4] nvmet-trace: avoid dereferencing pointer too early

[Daniel Wagner]

The first command issued from the host to the target is the fabrics
connect command. At this point, neither the target queue nor the
controller have been allocated. But we already try to trace this command
in nvmet_req_init.

Reported by KASAN.

Signed-off-by: Daniel Wagner <dwagner at suse.de>

---
 drivers/nvme/target/trace.c |  6 +++---
 drivers/nvme/target/trace.h | 24 +++++++++++++-----------
 2 files changed, 16 insertions(+), 14 deletions(-)

diff --git a/drivers/nvme/target/trace.h b/drivers/nvme/target/trace.h
index 6109b3806b12..6997bd7e45cf 100644
--- a/drivers/nvme/target/trace.h
+++ b/drivers/nvme/target/trace.h
@@ -32,18 +32,20 @@ const char *nvmet_trace_parse_fabrics_cmd(struct trace_seq *p, u8 fctype,
 	 nvmet_trace_parse_nvm_cmd(p, opcode, cdw10) :			\
 	 nvmet_trace_parse_admin_cmd(p, opcode, cdw10)))
 
-const char *nvmet_trace_ctrl_name(struct trace_seq *p, struct nvmet_ctrl *ctrl);
-#define __print_ctrl_name(ctrl)				\
-	nvmet_trace_ctrl_name(p, ctrl)
+const char *nvmet_trace_ctrl_id(struct trace_seq *p, u16 ctrl_id);
+#define __print_ctrl_id(ctrl_id)			\
+	nvmet_trace_ctrl_id(p, ctrl_id)
 
 const char *nvmet_trace_disk_name(struct trace_seq *p, char *name);
 #define __print_disk_name(name)				\
 	nvmet_trace_disk_name(p, name)
 
 #ifndef TRACE_HEADER_MULTI_READ
-static inline struct nvmet_ctrl *nvmet_req_to_ctrl(struct nvmet_req *req)
+static inline u16 nvmet_req_to_ctrl_id(struct nvmet_req *req)
 {
-	return req->sq->ctrl;
+	if (!req->sq || !req->sq->ctrl)
+		return 0;
+	return req->sq->ctrl->cntlid;
 }
 
 static inline void __assign_req_name(char *name, struct nvmet_req *req)
@@ -63,7 +65,7 @@ TRACE_EVENT(nvmet_req_init,
 	TP_ARGS(req, cmd),
 	TP_STRUCT__entry(
 		__field(struct nvme_command *, cmd)
-		__field(struct nvmet_ctrl *, ctrl)
+		__field(u16, ctrl_id)
 		__array(char, disk, DISK_NAME_LEN)
 		__field(int, qid)
 		__field(u16, cid)
@@ -76,7 +78,7 @@ TRACE_EVENT(nvmet_req_init,
 	),
 	TP_fast_assign(
 		__entry->cmd = cmd;
-		__entry->ctrl = nvmet_req_to_ctrl(req);
+		__entry->ctrl_id = nvmet_req_to_ctrl_id(req);
 		__assign_req_name(__entry->disk, req);
 		__entry->qid = req->sq->qid;
 		__entry->cid = cmd->common.command_id;
@@ -90,7 +92,7 @@ TRACE_EVENT(nvmet_req_init,
 	),
 	TP_printk("nvmet%s: %sqid=%d, cmdid=%u, nsid=%u, flags=%#x, "
 		  "meta=%#llx, cmd=(%s, %s)",
-		__print_ctrl_name(__entry->ctrl),
+		__print_ctrl_id(__entry->ctrl_id),
 		__print_disk_name(__entry->disk),
 		__entry->qid, __entry->cid, __entry->nsid,
 		__entry->flags, __entry->metadata,
@@ -104,7 +106,7 @@ TRACE_EVENT(nvmet_req_complete,
 	TP_PROTO(struct nvmet_req *req),
 	TP_ARGS(req),
 	TP_STRUCT__entry(
-		__field(struct nvmet_ctrl *, ctrl)
+		__field(u16, ctrl_id)
 		__array(char, disk, DISK_NAME_LEN)
 		__field(int, qid)
 		__field(int, cid)
@@ -112,7 +114,7 @@ TRACE_EVENT(nvmet_req_complete,
 		__field(u16, status)
 	),
 	TP_fast_assign(
-		__entry->ctrl = nvmet_req_to_ctrl(req);
+		__entry->ctrl_id = nvmet_req_to_ctrl_id(req);
 		__entry->qid = req->cq->qid;
 		__entry->cid = req->cqe->command_id;
 		__entry->result = le64_to_cpu(req->cqe->result.u64);
@@ -120,7 +122,7 @@ TRACE_EVENT(nvmet_req_complete,
 		__assign_req_name(__entry->disk, req);
 	),
 	TP_printk("nvmet%s: %sqid=%d, cmdid=%u, res=%#llx, status=%#x",
-		__print_ctrl_name(__entry->ctrl),
+		__print_ctrl_id(__entry->ctrl_id),
 		__print_disk_name(__entry->disk),
 		__entry->qid, __entry->cid, __entry->result, __entry->status)
 
-- 
2.41.0