4.12-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Johannes Thumshirn <jthumsh...@suse.de>

commit f930c7043663188429cd9b254e9d761edfc101ce upstream.

Don't make any assumptions on the sg_io_hdr_t::dxfer_direction or the
sg_io_hdr_t::dxferp in order to determine if it is a valid request. The
only way we can check for bad requests is by checking if the length
exceeds 256M.

Signed-off-by: Johannes Thumshirn <jthumsh...@suse.de>
Fixes: 28676d869bbb (scsi: sg: check for valid direction before starting the
request)
Reported-by: Jason L Tibbitts III <ti...@math.uh.edu>
Tested-by: Jason L Tibbitts III <ti...@math.uh.edu>
Suggested-by: Doug Gilbert <dgilb...@interlog.com>
Cc: Doug Gilbert <dgilb...@interlog.com>
Reviewed-by: Hannes Reinecke <h...@suse.com>
Signed-off-by: Martin K. Petersen <martin.peter...@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>


---
 drivers/scsi/sg.c |   25 +------------------------
 1 file changed, 1 insertion(+), 24 deletions(-)

--- a/drivers/scsi/sg.c
+++ b/drivers/scsi/sg.c
@@ -751,29 +751,6 @@ sg_new_write(Sg_fd *sfp, struct file *fi
        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)
@@ -794,7 +771,7 @@ sg_common_write(Sg_fd * sfp, Sg_request
                        "sg_common_write:  scsi opcode=0x%02x, cmd_size=%d\n",
                        (int) cmnd[0], (int) hp->cmd_len));
 
-       if (!sg_is_valid_dxfer(hp))
+       if (hp->dxfer_len >= SZ_256M)
                return -EINVAL;
 
        k = sg_start_req(srp, cmnd);


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