[SCSI] BUG_ON() impossible condition in sg list counting

If blk_rq_map_sg wrote more than was allocated in the scatterlist,
BUG_ON() is probably the right thing to do.

[jejb: rejections fixed up]

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Acked-by: Jens Axboe <jens.axboe@oracle.com>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>

2 files changed, 6 insertions, 20 deletions

diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index b0c59ae63a2f..aa17e718666e 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -1104,7 +1104,6 @@ void scsi_io_completion(struct scsi_cmnd *cmd, unsigned int good_bytes)
  *
  * Returns:     0 on success
  *              BLKPREP_DEFER if the failure is retryable
- *              BLKPREP_KILL if the failure is fatal
  */
 static int scsi_init_io(struct scsi_cmnd *cmd)
 {
@@ -1138,17 +1137,9 @@ static int scsi_init_io(struct scsi_cmnd *cmd)
          * each segment.
          */
         count = blk_rq_map_sg(req->q, req, cmd->request_buffer);
-        if (likely(count <= cmd->use_sg)) {
-                cmd->use_sg = count;
-                return BLKPREP_OK;
-        }
-
-        printk(KERN_ERR "Incorrect number of segments after building list\n");
-        printk(KERN_ERR "counted %d, received %d\n", count, cmd->use_sg);
-        printk(KERN_ERR "req nr_sec %lu, cur_nr_sec %u\n", req->nr_sectors,
-                        req->current_nr_sectors);
-
-        return BLKPREP_KILL;
+        BUG_ON(count > cmd->use_sg);
+        cmd->use_sg = count;
+        return BLKPREP_OK;
 }
 
 static struct scsi_cmnd *scsi_get_cmd_from_req(struct scsi_device *sdev,
diff --git a/drivers/scsi/scsi_tgt_lib.c b/drivers/scsi/scsi_tgt_lib.c
index 241815e911e7..93ece8f4e5de 100644
--- a/drivers/scsi/scsi_tgt_lib.c
+++ b/drivers/scsi/scsi_tgt_lib.c
@@ -368,14 +368,9 @@ static int scsi_tgt_init_cmd(struct scsi_cmnd *cmd, gfp_t gfp_mask)
         dprintk("cmd %p cnt %d %lu\n", cmd, scsi_sg_count(cmd),
                 rq_data_dir(rq));
         count = blk_rq_map_sg(rq->q, rq, scsi_sglist(cmd));
-        if (likely(count <= scsi_sg_count(cmd))) {
-                cmd->use_sg = count;
-                return 0;
-        }
-
-        eprintk("cmd %p cnt %d\n", cmd, scsi_sg_count(cmd));
-        scsi_free_sgtable(cmd);
-        return -EINVAL;
+        BUG_ON(count > cmd->use_sg);
+        cmd->use_sg = count;
+        return 0;
 }
 
 /* TODO: test this crap and replace bio_map_user with new interface maybe */