scsi: sg: check for valid direction before starting the request

commit 28676d869bbb5257b5f14c0c95ad3af3a7019dd5 upstream.

Check for a valid direction before starting the request, otherwise we
risk running into an assertion in the scsi midlayer checking for valid
requests.

[mkp: fixed typo]

Signed-off-by: Johannes Thumshirn <jthumshirn@suse.de>
Link: http://www.spinics.net/lists/linux-scsi/msg104400.html
Reported-by: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: Hannes Reinecke <hare@suse.com>
Tested-by: Johannes Thumshirn <jthumshirn@suse.de>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

1 files changed, 34 insertions, 12 deletions

diff --git a/drivers/scsi/sg.c b/drivers/scsi/sg.c
index 8a2285cab151a..198e60a004a61 100644
--- a/drivers/scsi/sg.c
+++ b/drivers/scsi/sg.c
@@ -701,18 +701,14 @@ sg_write(struct file *filp, const char __user *buf, size_t count, loff_t * ppos)
 	 * is a non-zero input_size, so emit a warning.
 	 */
 	if (hp->dxfer_direction == SG_DXFER_TO_FROM_DEV) {
-		static char cmd[TASK_COMM_LEN];
-		if (strcmp(current->comm, cmd)) {
-			printk_ratelimited(KERN_WARNING
-					   "sg_write: data in/out %d/%d bytes "
-					   "for SCSI command 0x%x-- guessing "
-					   "data in;\n   program %s not setting "
-					   "count and/or reply_len properly\n",
-					   old_hdr.reply_len - (int)SZ_SG_HEADER,
-					   input_size, (unsigned int) cmnd[0],
-					   current->comm);
-			strcpy(cmd, current->comm);
-		}
+		printk_ratelimited(KERN_WARNING
+				   "sg_write: data in/out %d/%d bytes "
+				   "for SCSI command 0x%x-- guessing "
+				   "data in;\n   program %s not setting "
+				   "count and/or reply_len properly\n",
+				   old_hdr.reply_len - (int)SZ_SG_HEADER,
+				   input_size, (unsigned int) cmnd[0],
+				   current->comm);
 	}
 	k = sg_common_write(sfp, srp, cmnd, sfp->timeout, blocking);
 	return (k < 0) ? k : count;
@@ -790,6 +786,29 @@ sg_new_write(Sg_fd *sfp, struct file *file, const char __user *buf,
 	return count;
 }
 
+static bool sg_is_valid_dxfer(sg_io_hdr_t *hp)
+{
+	switch (hp->dxfer_direction) {
+	case SG_DXFER_NONE:
+		if (hp->dxferp || hp->dxfer_len > 0)
+			return false;
+		return true;
+	case SG_DXFER_TO_DEV:
+	case SG_DXFER_FROM_DEV:
+	case SG_DXFER_TO_FROM_DEV:
+		if (!hp->dxferp || hp->dxfer_len == 0)
+			return false;
+		return true;
+	case SG_DXFER_UNKNOWN:
+		if ((!hp->dxferp && hp->dxfer_len) ||
+		    (hp->dxferp && hp->dxfer_len == 0))
+			return false;
+		return true;
+	default:
+		return false;
+	}
+}
+
 static int
 sg_common_write(Sg_fd * sfp, Sg_request * srp,
 		unsigned char *cmnd, int timeout, int blocking)
@@ -809,6 +828,9 @@ sg_common_write(Sg_fd * sfp, Sg_request * srp,
 	SCSI_LOG_TIMEOUT(4, printk("sg_common_write:  scsi opcode=0x%02x, cmd_size=%d\n",
 			  (int) cmnd[0], (int) hp->cmd_len));
 
+	if (!sg_is_valid_dxfer(hp))
+		return -EINVAL;
+
 	k = sg_start_req(srp, cmnd);
 	if (k) {
 		SCSI_LOG_TIMEOUT(1, printk("sg_common_write: start_req err=%d\n", k));