zfcp: fix payload trace length for SAN request&response

commit 94db3725 upstream.

commit 2c55b750
("[SCSI] zfcp: Redesign of the debug tracing for SAN records.")
started to add FC_CT_HDR_LEN which made zfcp dump random data
out of bounds for RSPN GS responses because u.rspn.rsp
is the largest and last field in the union of struct zfcp_fc_req.
Other request/response types only happened to stay within bounds
due to the padding of the union or
due to the trace capping of u.gspn.rsp to ZFCP_DBF_SAN_MAX_PAYLOAD.

Timestamp      : ...
Area           : SAN
Subarea        : 00
Level          : 1
Exception      : -
CPU id         : ..
Caller         : ...
Record id      : 2
Tag            : fsscth2
Request id     : 0x...
Destination ID : 0x00fffffc
Payload short  : 01000000 fc020000 80020000 00000000
                 xxxxxxxx xxxxxxxx xxxxxxxx xxxxxxxx <===
                 00000000 00000000 00000000 00000000
Payload length : 32                                  <===

struct zfcp_fc_req {
    [0] struct zfcp_fsf_ct_els ct_els;
   [56] struct scatterlist sg_req;
   [96] struct scatterlist sg_rsp;
        union {
            struct {req; rsp;} adisc;    SIZE: 28+28=   56
            struct {req; rsp;} gid_pn;   SIZE: 24+20=   44
            struct {rspsg; req;} gpn_ft; SIZE: 40*4+20=180
            struct {req; rsp;} gspn;     SIZE: 20+273= 293
            struct {req; rsp;} rspn;     SIZE: 277+16= 293
  [136] } u;
}
SIZE: 432
Signed-off-by: Steffen Maier <maier@linux.vnet.ibm.com>
Fixes: 2c55b750 ("[SCSI] zfcp: Redesign of the debug tracing for SAN records.")
Reviewed-by: Alexey Ishchuk <aishchuk@linux.vnet.ibm.com>
Reviewed-by: Benjamin Block <bblock@linux.vnet.ibm.com>
Reviewed-by: Hannes Reinecke <hare@suse.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

drivers/s390/scsi/zfcp_dbf.c

@@ -389,7 +389,7 @@ void zfcp_dbf_san_req(char *tag, struct zfcp_fsf_req *fsf, u32 d_id)
 	struct zfcp_fsf_ct_els *ct_els = fsf->data;
 	u16 length;
 
-	length = (u16)(ct_els->req->length + FC_CT_HDR_LEN);
+	length = (u16)(ct_els->req->length);
 	zfcp_dbf_san(tag, dbf, sg_virt(ct_els->req), ZFCP_DBF_SAN_REQ, length,
 		     fsf->req_id, d_id);
 }
@@ -405,7 +405,7 @@ void zfcp_dbf_san_res(char *tag, struct zfcp_fsf_req *fsf)
 	struct zfcp_fsf_ct_els *ct_els = fsf->data;
 	u16 length;
 
-	length = (u16)(ct_els->resp->length + FC_CT_HDR_LEN);
+	length = (u16)(ct_els->resp->length);
 	zfcp_dbf_san(tag, dbf, sg_virt(ct_els->resp), ZFCP_DBF_SAN_RES, length,
 		     fsf->req_id, ct_els->d_id);
 }