[PATCH v4] scsi: scsi_transport_fc: widen FPIN pname walker counter to u32

[Michael Bommarito <michael.bommarito@gmail.com>]

An adjacent Fibre Channel fabric actor that can deliver an FPIN ELS
frame to an lpfc or qla2xxx Linux initiator can trigger a non-return
in the generic FC transport. This is not a local userspace or IP
network path; the attacker must be able to inject fabric traffic, for
example as a compromised switch or fabric controller, or as a same-zone
N_Port on a fabric that permits source spoofing.

The Link-Integrity and Peer-Congestion FPIN walkers used a u8 loop
counter against the 32-bit on-wire pname_count field, and did not bound
pname_count by the descriptor body already validated by the TLV walker.
A pname_count of 256 therefore wraps the counter and keeps the loop
condition true indefinitely.

Factor the shared pname_list[] walk into one helper, widen the counter
to u32, and clamp pname_count against the entries that fit in the
descriptor body before iterating.

Fixes: 3dcfe0de5a97 ("scsi: fc: Parse FPIN packets and update statistics")
Cc: stable@vger.kernel.org
Assisted-by: Claude:claude-opus-4-7
Signed-off-by: Michael Bommarito <michael.bommarito@gmail.com>
---
Changes in v4:
- Use min() rather than min_t(u32, ...) for the pname_count clamp and
  fold away the temporary max_count variable, as David Laight suggested.

Changes in v3:
- State the fabric-adjacent threat model explicitly in the commit
  message and clarify that this is not local userspace or IP-network
  reachable.
- Use min_t(u32, ...) for the pname_count clamp, as Christoph suggested.
- Use FC_TLV_DESC_LENGTH_FROM_SZ() instead of open-coding the descriptor
  body length calculation.
- Factor the duplicate LI and peer-congestion pname walker into a common
  helper while preserving the LI-only host-stat update.

Changes in v2:
- Drop the redundant cover letter shipped with v1.  A single-patch send
  does not need one, and the v1 cover carried stale draft markers.

 drivers/scsi/scsi_transport_fc.c | 77 +++++++++++++++++---------------
 1 file changed, 41 insertions(+), 36 deletions(-)

diff --git a/drivers/scsi/scsi_transport_fc.c b/drivers/scsi/scsi_transport_fc.c
index dce95e361daf0..173ed6373f04b 100644
--- a/drivers/scsi/scsi_transport_fc.c
+++ b/drivers/scsi/scsi_transport_fc.c
@@ -737,6 +737,37 @@ fc_cn_stats_update(u16 event_type, struct fc_fpin_stats *stats)
 	}
 }
 
+static void
+fc_fpin_pname_stats_update(struct Scsi_Host *shost,
+			   struct fc_rport *attach_rport, u16 event_type,
+			   u32 desc_len, u32 fixed_len, u32 pname_count,
+			   __be64 *pname_list,
+			   void (*stats_update)(u16 event_type,
+						struct fc_fpin_stats *stats))
+{
+	u32 i;
+	struct fc_rport *rport;
+	u64 wwpn;
+
+	if (desc_len < fixed_len)
+		pname_count = 0;
+	else
+		pname_count = min(pname_count, (desc_len - fixed_len) /
+				   sizeof(pname_list[0]));
+
+	for (i = 0; i < pname_count; i++) {
+		wwpn = be64_to_cpu(pname_list[i]);
+		rport = fc_find_rport_by_wwpn(shost, wwpn);
+		if (rport &&
+		    (rport->roles & FC_PORT_ROLE_FCP_TARGET ||
+		     rport->roles & FC_PORT_ROLE_NVME_TARGET)) {
+			if (rport == attach_rport)
+				continue;
+			stats_update(event_type, &rport->fpin_stats);
+		}
+	}
+}
+
 /*
  * fc_fpin_li_stats_update - routine to update Link Integrity
  * event statistics.
@@ -747,13 +778,11 @@ fc_cn_stats_update(u16 event_type, struct fc_fpin_stats *stats)
 static void
 fc_fpin_li_stats_update(struct Scsi_Host *shost, struct fc_tlv_desc *tlv)
 {
-	u8 i;
 	struct fc_rport *rport = NULL;
 	struct fc_rport *attach_rport = NULL;
 	struct fc_host_attrs *fc_host = shost_to_fc_host(shost);
 	struct fc_fn_li_desc *li_desc = (struct fc_fn_li_desc *)tlv;
 	u16 event_type = be16_to_cpu(li_desc->event_type);
-	u64 wwpn;
 
 	rport = fc_find_rport_by_wwpn(shost,
 				      be64_to_cpu(li_desc->attached_wwpn));
@@ -764,22 +793,11 @@ fc_fpin_li_stats_update(struct Scsi_Host *shost, struct fc_tlv_desc *tlv)
 		fc_li_stats_update(event_type, &attach_rport->fpin_stats);
 	}
 
-	if (be32_to_cpu(li_desc->pname_count) > 0) {
-		for (i = 0;
-		    i < be32_to_cpu(li_desc->pname_count);
-		    i++) {
-			wwpn = be64_to_cpu(li_desc->pname_list[i]);
-			rport = fc_find_rport_by_wwpn(shost, wwpn);
-			if (rport &&
-			    (rport->roles & FC_PORT_ROLE_FCP_TARGET ||
-			    rport->roles & FC_PORT_ROLE_NVME_TARGET)) {
-				if (rport == attach_rport)
-					continue;
-				fc_li_stats_update(event_type,
-						   &rport->fpin_stats);
-			}
-		}
-	}
+	fc_fpin_pname_stats_update(shost, attach_rport, event_type,
+				   be32_to_cpu(li_desc->desc_len),
+				   FC_TLV_DESC_LENGTH_FROM_SZ(*li_desc),
+				   be32_to_cpu(li_desc->pname_count),
+				   li_desc->pname_list, fc_li_stats_update);
 
 	if (fc_host->port_name == be64_to_cpu(li_desc->attached_wwpn))
 		fc_li_stats_update(event_type, &fc_host->fpin_stats);
@@ -827,13 +845,11 @@ static void
 fc_fpin_peer_congn_stats_update(struct Scsi_Host *shost,
 				struct fc_tlv_desc *tlv)
 {
-	u8 i;
 	struct fc_rport *rport = NULL;
 	struct fc_rport *attach_rport = NULL;
 	struct fc_fn_peer_congn_desc *pc_desc =
 	    (struct fc_fn_peer_congn_desc *)tlv;
 	u16 event_type = be16_to_cpu(pc_desc->event_type);
-	u64 wwpn;
 
 	rport = fc_find_rport_by_wwpn(shost,
 				      be64_to_cpu(pc_desc->attached_wwpn));
@@ -844,22 +860,11 @@ fc_fpin_peer_congn_stats_update(struct Scsi_Host *shost,
 		fc_cn_stats_update(event_type, &attach_rport->fpin_stats);
 	}
 
-	if (be32_to_cpu(pc_desc->pname_count) > 0) {
-		for (i = 0;
-		    i < be32_to_cpu(pc_desc->pname_count);
-		    i++) {
-			wwpn = be64_to_cpu(pc_desc->pname_list[i]);
-			rport = fc_find_rport_by_wwpn(shost, wwpn);
-			if (rport &&
-			    (rport->roles & FC_PORT_ROLE_FCP_TARGET ||
-			     rport->roles & FC_PORT_ROLE_NVME_TARGET)) {
-				if (rport == attach_rport)
-					continue;
-				fc_cn_stats_update(event_type,
-						   &rport->fpin_stats);
-			}
-		}
-	}
+	fc_fpin_pname_stats_update(shost, attach_rport, event_type,
+				   be32_to_cpu(pc_desc->desc_len),
+				   FC_TLV_DESC_LENGTH_FROM_SZ(*pc_desc),
+				   be32_to_cpu(pc_desc->pname_count),
+				   pc_desc->pname_list, fc_cn_stats_update);
 }
 
 /*
-- 
2.53.0