Re: [syzbot] [block?] WARNING in blk_rq_map_user_iov

[Ricardo B. Marliere]

Flag iter as the data source if dxfer_direction is set to
SG_DXFER_TO_DEV or SG_DXFER_TO_FROM_DEV.

#syz test: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master

diff --git a/drivers/scsi/sg.c b/drivers/scsi/sg.c
index 0d8afffd1683..991c6554bef4 100644
--- a/drivers/scsi/sg.c
+++ b/drivers/scsi/sg.c
@@ -1737,8 +1737,13 @@ sg_start_req(Sg_request *srp, unsigned char *cmd)
        Sg_scatter_hold *rsv_schp = &sfp->reserve;
        struct request_queue *q = sfp->parentdp->device->request_queue;
        struct rq_map_data *md, map_data;
-       int rw = hp->dxfer_direction == SG_DXFER_TO_DEV ? ITER_SOURCE : ITER_DEST;
        struct scsi_cmnd *scmd;
+       int rw;
+       if (hp->dxfer_direction == SG_DXFER_TO_DEV ||
+           hp->dxfer_direction == SG_DXFER_TO_FROM_DEV)
+               rw = ITER_SOURCE;
+       else
+               rw = ITER_DEST;

        SCSI_LOG_TIMEOUT(4, sg_printk(KERN_INFO, sfp->parentdp,
                                      "sg_start_req: dxfer_len=%d\n",