CVE-2026-74556

In the Linux kernel, the following vulnerability has been resolved:

scsi: libiscsi_tcp: Bound SCSI Response data segment to the connection buffer

iscsitcphdr_dissect() receives the data segment of several PDU types

into the fixed-size conn->data buffer, which is allocated for

ISCSIDEFMAXRECVSEGLEN (8192) bytes.  For the LOGINRSP, TEXT_RSP,

REJECT and ASYNC_EVENT opcodes the dissect path already rejects a PDU

whose DataSegmentLength exceeds that buffer.

The SCSI Command Response (ISCSIOPSCSICMDRSP) path also copies its

data segment (sense/response data) into conn->data via

iscsitcpdatarecvprep(), but it does so without the same check.  The

only upstream bound on in.datalen is conn->maxrecvdlength, the

initiator's advertised MaxRecvDataSegmentLength, which is commonly

negotiated well above 8192 (open-iscsi defaults to 262144).  A target

that returns a SCSI Response with a DataSegmentLength between 8193 and

maxrecvdlength therefore overflows the 8192-byte conn->data buffer.

Once the same bound applies, ISCSIOPSCSICMDRSP is handled exactly

like those responses: bound the data segment, receive it into conn->data

when present, and otherwise complete the PDU with no data.  Fold the

opcode into that case group rather than duplicating the check.