bsg: Fix sense buffer bug in SG_IO

When submitting requests via SG_IO, which does a sync io, a
bsg_command is not allocated. So an in-Kernel sense_buffer was not
set. However when calling blk_execute_rq() with no sense buffer
one is provided from the stack. Now bsg at blk_complete_sgv4_hdr_rq()
would check if rq->sense_len and a sense was requested by sg_io_v4
the rq->sense was copy_user() back, but by now it is already mangled
stack memory.

I have fixed that by forcing a sense_buffer when calling bsg_map_hdr().
The bsg_command->sense is provided in the write/read path like before,
and on-the-stack buffer is provided when doing SG_IO.

I have also fixed a dprintk message to print rq->errors in hex because
of the scsi bit-field use of this member. For other block devices it
does not matter anyway.

Signed-off-by: Boaz Harrosh <[e-mail]>
Acked-by: FUJITA Tomonori <[e-mail]>
Signed-off-by: Jens Axboe <[e-mail]>

block/bsg.c

···
  * map sg_io_v4 to a request.
  */
 static struct request *
-bsg_map_hdr(struct bsg_device *bd, struct sg_io_v4 *hdr, fmode_t has_write_perm)
+bsg_map_hdr(struct bsg_device *bd, struct sg_io_v4 *hdr, fmode_t has_write_perm,
+	    u8 *sense)
 {
 	struct request_queue *q = bd->queue;
 	struct request *rq, *next_rq = NULL;
···
 		if (ret)
 			goto out;
 	}
+
+	rq->sense = sense;
+	rq->sense_len = 0;
+
 	return rq;
 out:
 	if (rq->cmd != rq->__cmd)
···
 static void bsg_add_command(struct bsg_device *bd, struct request_queue *q,
 			    struct bsg_command *bc, struct request *rq)
 {
-	rq->sense = bc->sense;
-	rq->sense_len = 0;
-
 	/*
 	 * add bc command to busy queue and submit rq for io
 	 */
···
 {
 	int ret = 0;
 
-	dprintk("rq %p bio %p %u\n", rq, bio, rq->errors);
+	dprintk("rq %p bio %p 0x%x\n", rq, bio, rq->errors);
 	/*
 	 * fill in all the output members
 	 */
···
 		/*
 		 * get a request, fill in the blanks, and add to request queue
 		 */
-		rq = bsg_map_hdr(bd, &bc->hdr, has_write_perm);
+		rq = bsg_map_hdr(bd, &bc->hdr, has_write_perm, bc->sense);
 		if (IS_ERR(rq)) {
 			ret = PTR_ERR(rq);
 			rq = NULL;
···
 		struct request *rq;
 		struct bio *bio, *bidi_bio = NULL;
 		struct sg_io_v4 hdr;
+		u8 sense[SCSI_SENSE_BUFFERSIZE];
 
 		if (copy_from_user(&hdr, uarg, sizeof(hdr)))
 			return -EFAULT;
 
-		rq = bsg_map_hdr(bd, &hdr, file->f_mode & FMODE_WRITE);
+		rq = bsg_map_hdr(bd, &hdr, file->f_mode & FMODE_WRITE, sense);
 		if (IS_ERR(rq))
 			return PTR_ERR(rq);