Messages in this thread Patch in this message |  | | From | carlos.bilbao@kernel ... | | Subject | [PATCH v2] scsi: target: iscsi: reject invalid size Extended CDB AHS | | Date | Wed, 8 Apr 2026 19:42:53 -0700 |
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From: Carlos Bilbao <carlos.bilbao@kernel.org>
If ecdb_ahdr->ahslength is zero, two bugs follow:
kmalloc(be16_to_cpu(ecdb_ahdr->ahslength) + 15, ...)
allocates 15 bytes, but the immediately following memcpy writes ISCSI_CDB_SIZE (16) bytes into it, a one-byte heap overflow. Also:
memcpy(cdb + ISCSI_CDB_SIZE, ecdb_ahdr->ecdb, be16_to_cpu(ecdb_ahdr->ahslength) - 1);
(u16)0 - 1 promotes to (int)-1 which converts to SIZE_MAX as size_t, causing a massive out-of-bounds write.
Reject ahslength == 0 with ISCSI_REASON_PROTOCOL_ERROR before the kmalloc. Also reject ahslength values that exceed the actual AHS buffer advertised.
Changes in v2:
- Add bounds check: ahslength must not exceed (hdr->hlength * 4) - 3. - Replace opaque ahslength + 15 with explicit cdb_length variable.
Fixes: 8f1f7d297bce ("scsi: target: iscsi: Add support for extended CDB AHS") Signed-off-by: Carlos Bilbao (Lambda) <carlos.bilbao@kernel.org> --- drivers/target/iscsi/iscsi_target.c | 23 +++++++++++++++++++---- 1 file changed, 19 insertions(+), 4 deletions(-)
diff --git a/drivers/target/iscsi/iscsi_target.c b/drivers/target/iscsi/iscsi_target.c index e80449f6ce15..1a492965ebdf 100644 --- a/drivers/target/iscsi/iscsi_target.c +++ b/drivers/target/iscsi/iscsi_target.c @@ -1100,6 +1100,8 @@ int iscsit_setup_scsi_cmd(struct iscsit_conn *conn, struct iscsit_cmd *cmd, cdb = hdr->cdb; if (hdr->hlength) { + u16 ahslength; + ecdb_ahdr = (struct iscsi_ecdb_ahdr *) (hdr + 1); if (ecdb_ahdr->ahstype != ISCSI_AHSTYPE_CDB) { pr_err("Additional Header Segment type %d not supported!\n", @@ -1108,14 +1110,27 @@ int iscsit_setup_scsi_cmd(struct iscsit_conn *conn, struct iscsit_cmd *cmd, ISCSI_REASON_CMD_NOT_SUPPORTED, buf); } - cdb = kmalloc(be16_to_cpu(ecdb_ahdr->ahslength) + 15, - GFP_KERNEL); + ahslength = be16_to_cpu(ecdb_ahdr->ahslength); + if (!ahslength) { + pr_err("Extended CDB AHS with zero length, protocol error.\n"); + return iscsit_add_reject_cmd(cmd, + ISCSI_REASON_PROTOCOL_ERROR, buf); + } + if (ahslength > (hdr->hlength * 4) - 3) { + pr_err("Extended CDB AHS length %u exceeds available buffer.\n", + ahslength); + return iscsit_add_reject_cmd(cmd, + ISCSI_REASON_PROTOCOL_ERROR, buf); + } + + u16 cdb_length = ahslength - 1 + ISCSI_CDB_SIZE; + + cdb = kmalloc(cdb_length, GFP_KERNEL); if (cdb == NULL) return iscsit_add_reject_cmd(cmd, ISCSI_REASON_BOOKMARK_NO_RESOURCES, buf); memcpy(cdb, hdr->cdb, ISCSI_CDB_SIZE); - memcpy(cdb + ISCSI_CDB_SIZE, ecdb_ahdr->ecdb, - be16_to_cpu(ecdb_ahdr->ahslength) - 1); + memcpy(cdb + ISCSI_CDB_SIZE, ecdb_ahdr->ecdb, cdb_length - ISCSI_CDB_SIZE); } data_direction = (hdr->flags & ISCSI_FLAG_CMD_WRITE) ? DMA_TO_DEVICE : -- 2.43.0
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