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

[Hannes Reinecke]

On 5/20/26 15:30, Michael Bommarito wrote:
> 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@xxxxxxxxxxxxxxx
> Assisted-by: Claude:claude-opus-4-7
> Signed-off-by: Michael Bommarito <michael.bommarito@xxxxxxxxx>
> ---
> 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(-)
Reviewed-by: Hannes Reinecke <hare@xxxxxxx>

Cheers,

Hannes
--
Dr. Hannes Reinecke                  Kernel Storage Architect
hare@xxxxxxx                                +49 911 74053 688
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