[18/19] target/iscsi: Avoid that CDB parser bugs trigger a kernel crash
diff mbox

Message ID 20170504225102.8931-19-bart.vanassche@sandisk.com
State New, archived
Headers show

Commit Message

Bart Van Assche May 4, 2017, 10:51 p.m. UTC
If the code for parsing a CDB sets se_cmd.data_length to a value
that is lower than the size of the SCSI Data-Out buffer then a
buffer overflow occurs in the iSCSI target driver while receiving
the Data-Out buffer. Make the code for receiving that buffer more
robust by checking the bounds of the allocated iovec. This patch
fixes the following crash:

BUG: unable to handle kernel NULL pointer dereference at 00000000
00000014
RIP: 0010:iscsit_map_iovec+0x120/0x190 [iscsi_target_mod]
Call Trace:
 iscsit_get_rx_pdu+0x8a2/0xe00 [iscsi_target_mod]
 iscsi_target_rx_thread+0x6e/0xa0 [iscsi_target_mod]
 kthread+0x109/0x140

Signed-off-by: Bart Van Assche <bart.vanassche@sandisk.com>
Cc: Hannes Reinecke <hare@suse.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Andy Grover <agrover@redhat.com>
Cc: David Disseldorp <ddiss@suse.de>
---
 drivers/target/iscsi/iscsi_target.c | 40 +++++++++++++++++++++++++++++--------
 1 file changed, 32 insertions(+), 8 deletions(-)

Patch
diff mbox

diff --git a/drivers/target/iscsi/iscsi_target.c b/drivers/target/iscsi/iscsi_target.c
index ef1bb12ee61e..928696ef5148 100644
--- a/drivers/target/iscsi/iscsi_target.c
+++ b/drivers/target/iscsi/iscsi_target.c
@@ -575,7 +575,8 @@  iscsit_xmit_nondatain_pdu(struct iscsi_conn *conn, struct iscsi_cmd *cmd,
 	return 0;
 }
 
-static int iscsit_map_iovec(struct iscsi_cmd *, struct kvec *, u32, u32);
+static int iscsit_map_iovec(struct iscsi_cmd *, struct kvec *, u32 nvec,
+			    u32, u32);
 static void iscsit_unmap_iovec(struct iscsi_cmd *);
 static u32 iscsit_do_crypto_hash_sg(struct ahash_request *, struct iscsi_cmd *,
 				    u32, u32, u32, u8 *);
@@ -606,7 +607,8 @@  iscsit_xmit_datain_pdu(struct iscsi_conn *conn, struct iscsi_cmd *cmd,
 			 *header_digest);
 	}
 
-	iov_ret = iscsit_map_iovec(cmd, &cmd->iov_data[1],
+	iov_ret = iscsit_map_iovec(cmd, &cmd->iov_data[iov_count],
+				   cmd->orig_iov_data_count - (iov_count + 2),
 				   datain->offset, datain->length);
 	if (iov_ret < 0)
 		return -1;
@@ -892,10 +894,11 @@  EXPORT_SYMBOL(iscsit_reject_cmd);
 static int iscsit_map_iovec(
 	struct iscsi_cmd *cmd,
 	struct kvec *iov,
+	u32 nvec,
 	u32 data_offset,
 	u32 data_length)
 {
-	u32 i = 0;
+	u32 i = 0, orig_data_length = data_length;
 	struct scatterlist *sg;
 	unsigned int page_off;
 
@@ -906,7 +909,7 @@  static int iscsit_map_iovec(
 
 	if (ent >= cmd->se_cmd.t_data_nents) {
 		pr_err("Initial page entry out-of-bounds\n");
-		return -1;
+		goto overflow;
 	}
 
 	sg = &cmd->se_cmd.t_data_sg[ent];
@@ -916,7 +919,12 @@  static int iscsit_map_iovec(
 	cmd->first_data_sg_off = page_off;
 
 	while (data_length) {
-		u32 cur_len = min_t(u32, data_length, sg->length - page_off);
+		u32 cur_len;
+
+		if (WARN_ON_ONCE(!sg || i >= nvec))
+			goto overflow;
+
+		cur_len = min_t(u32, data_length, sg->length - page_off);
 
 		iov[i].iov_base = kmap(sg_page(sg)) + sg->offset + page_off;
 		iov[i].iov_len = cur_len;
@@ -930,6 +938,16 @@  static int iscsit_map_iovec(
 	cmd->kmapped_nents = i;
 
 	return i;
+
+overflow:
+	pr_err("offset %d + length %d overflow; %d/%d; sg-list:\n",
+	       data_offset, orig_data_length, i, nvec);
+	for_each_sg(cmd->se_cmd.t_data_sg, sg,
+		    cmd->se_cmd.t_data_nents, i) {
+		pr_err("[%d] off %d len %d\n",
+		       i, sg->offset, sg->length);
+	}
+	return -1;
 }
 
 static void iscsit_unmap_iovec(struct iscsi_cmd *cmd)
@@ -1577,8 +1595,8 @@  iscsit_get_dataout(struct iscsi_conn *conn, struct iscsi_cmd *cmd,
 	rx_size += payload_length;
 	iov = &cmd->iov_data[0];
 
-	iov_ret = iscsit_map_iovec(cmd, iov, be32_to_cpu(hdr->offset),
-				   payload_length);
+	iov_ret = iscsit_map_iovec(cmd, iov, cmd->orig_iov_data_count - 2,
+				   be32_to_cpu(hdr->offset), payload_length);
 	if (iov_ret < 0)
 		return -1;
 
@@ -1598,6 +1616,7 @@  iscsit_get_dataout(struct iscsi_conn *conn, struct iscsi_cmd *cmd,
 		rx_size += ISCSI_CRC_LEN;
 	}
 
+	WARN_ON_ONCE(iov_count >= cmd->orig_iov_data_count);
 	rx_got = rx_data(conn, &cmd->iov_data[0], iov_count, rx_size);
 
 	iscsit_unmap_iovec(cmd);
@@ -1863,6 +1882,7 @@  static int iscsit_handle_nop_out(struct iscsi_conn *conn, struct iscsi_cmd *cmd,
 			rx_size += ISCSI_CRC_LEN;
 		}
 
+		WARN_ON_ONCE(niov >= cmd->orig_iov_data_count);
 		rx_got = rx_data(conn, &cmd->iov_misc[0], niov, rx_size);
 		if (rx_got != rx_size) {
 			ret = -1;
@@ -2273,6 +2293,7 @@  iscsit_handle_text_cmd(struct iscsi_conn *conn, struct iscsi_cmd *cmd,
 			rx_size += ISCSI_CRC_LEN;
 		}
 
+		WARN_ON_ONCE(niov >= cmd->orig_iov_data_count);
 		rx_got = rx_data(conn, &iov[0], niov, rx_size);
 		if (rx_got != rx_size)
 			goto reject;
@@ -2585,7 +2606,9 @@  static int iscsit_handle_immediate_data(
 	struct iscsi_conn *conn = cmd->conn;
 	struct kvec *iov;
 
-	iov_ret = iscsit_map_iovec(cmd, cmd->iov_data, cmd->write_data_done, length);
+	iov_ret = iscsit_map_iovec(cmd, cmd->iov_data,
+				   cmd->orig_iov_data_count - 2,
+				   cmd->write_data_done, length);
 	if (iov_ret < 0)
 		return IMMEDIATE_DATA_CANNOT_RECOVER;
 
@@ -2606,6 +2629,7 @@  static int iscsit_handle_immediate_data(
 		rx_size += ISCSI_CRC_LEN;
 	}
 
+	WARN_ON_ONCE(iov_count >= cmd->orig_iov_data_count);
 	rx_got = rx_data(conn, &cmd->iov_data[0], iov_count, rx_size);
 
 	iscsit_unmap_iovec(cmd);