libiscsi: fix potential buffer overrun in __iscsi_conn_send_pdu

This patches fixes a potential buffer overrun in __iscsi_conn_send_pdu.
This function is used by iscsi drivers and userspace to send iscsi PDUs/
commands. For login commands, we have a set buffer size. For all other
commands we do not support data buffers.

This was reported by Dan Carpenter here:
http://www.spinics.net/lists/linux-scsi/msg66838.html

Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Mike Christie <michaelc@cs.wisc.edu>
Reviewed-by: Sagi Grimberg <sagig@mellanox.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>

1 files changed, 10 insertions, 0 deletions

diff --git a/drivers/scsi/libiscsi.c b/drivers/scsi/libiscsi.c
index ea025e4806b6..191b59793519 100644
--- a/drivers/scsi/libiscsi.c
+++ b/drivers/scsi/libiscsi.c
@@ -717,11 +717,21 @@ __iscsi_conn_send_pdu(struct iscsi_conn *conn, struct iscsi_hdr *hdr,
                         return NULL;
                 }
 
+                if (data_size > ISCSI_DEF_MAX_RECV_SEG_LEN) {
+                        iscsi_conn_printk(KERN_ERR, conn, "Invalid buffer len of %u for login task. Max len is %u\n", data_size, ISCSI_DEF_MAX_RECV_SEG_LEN);
+                        return NULL;
+                }
+
                 task = conn->login_task;
         } else {
                 if (session->state != ISCSI_STATE_LOGGED_IN)
                         return NULL;
 
+                if (data_size != 0) {
+                        iscsi_conn_printk(KERN_ERR, conn, "Can not send data buffer of len %u for op 0x%x\n", data_size, opcode);
+                        return NULL;
+                }
+
                 BUG_ON(conn->c_stage == ISCSI_CONN_INITIAL_STAGE);
                 BUG_ON(conn->c_stage == ISCSI_CONN_STOPPED);