nvmet: passthru: fix OOB reads when parsing ns id descriptor list

nvmet_passthru_override_id_descs() walks a namespace identification
descriptor list populated from the underlying passthru controller's
Identify response, which is device reported. The loop advanced pos by
device controlled amounts (sizeof(*cur) + nidl) without checking that
the next descriptor header actually fits inside the buffer, so a
malicious device could push pos to within a few bytes of the buffer end
and cause cur->nidl, cur->nidt or the reserved field to be read past the
allocation.

Additionally, when a CSI descriptor lands exactly at the last valid
header offset, cur + 1 points one byte past the end of the buffer.
The unconditional memcpy(&csi, cur + 1, NVME_NIDT_CSI_LEN) could read
that out-of-bounds byte and copy it back to the initiator via
nvmet_copy_to_sgl(), leaking adjacent heap memory.

Bounds check both the descriptor header and the CSI value before
dereferencing them.

Signed-off-by: Hari Mishal <harimishal1@gmail.com>
Signed-off-by: Keith Busch <kbusch@kernel.org>

drivers/nvme/target/passthru.c

@@ -53,13 +53,22 @@ static u16 nvmet_passthru_override_id_descs(struct nvmet_req *req)
 	for (pos = 0; pos < NVME_IDENTIFY_DATA_SIZE; pos += len) {
 		struct nvme_ns_id_desc *cur = data + pos;
 
+		if (pos + sizeof(*cur) > NVME_IDENTIFY_DATA_SIZE)
+			break;
+
 		if (cur->nidl == 0)
 			break;
+
 		if (cur->nidt == NVME_NIDT_CSI) {
+			if (pos + sizeof(*cur) + NVME_NIDT_CSI_LEN >
+						NVME_IDENTIFY_DATA_SIZE)
+				break;
+
 			memcpy(&csi, cur + 1, NVME_NIDT_CSI_LEN);
 			csi_seen = true;
 			break;
 		}
+
 		len = sizeof(struct nvme_ns_id_desc) + cur->nidl;
 	}