| From | Ben Hutchings <> | Date | Wed, 27 Apr 2016 01:02:21 +0200 | Subject | [PATCH 3.16 086/217] sg: fix dxferp in from_to case |
| |
3.16.35-rc1 review patch. If anyone has any objections, please let me know.
------------------
From: Douglas Gilbert <dgilbert@interlog.com>
commit 5ecee0a3ee8d74b6950cb41e8989b0c2174568d4 upstream.
One of the strange things that the original sg driver did was let the user provide both a data-out buffer (it followed the sg_header+cdb) _and_ specify a reply length greater than zero. What happened was that the user data-out buffer was copied into some kernel buffers and then the mid level was told a read type operation would take place with the data from the device overwriting the same kernel buffers. The user would then read those kernel buffers back into the user space.
=46romwhat I can tell, the above action was broken by commit fad7f01e61bf ("sg: set dxferp to NULL for READ with the older SG interface") in 2008 and syzkaller found that out recently.
Make sure that a user space pointer is passed through when data follows the sg_header structure and command. Fix the abnormal case when a non-zero reply_len is also given.
Fixes: fad7f01e61bf737fe8a3740d803f000db57ecac6 Signed-off-by: Douglas Gilbert <dgilbert@interlog.com> Reviewed-by: Ewan Milne <emilne@redhat.com> Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com> Signed-off-by: Ben Hutchings <ben@decadent.org.uk> --- drivers/scsi/sg.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
--- a/drivers/scsi/sg.c +++ b/drivers/scsi/sg.c @@ -633,7 +633,8 @@ sg_write(struct file *filp, const char _ else hp->dxfer_direction = (mxsize > 0) ? SG_DXFER_FROM_DEV : SG_DXFER_NONE; hp->dxfer_len = mxsize; - if (hp->dxfer_direction == SG_DXFER_TO_DEV) + if ((hp->dxfer_direction == SG_DXFER_TO_DEV) || + (hp->dxfer_direction == SG_DXFER_TO_FROM_DEV)) hp->dxferp = (char __user *)buf + cmd_size; else hp->dxferp = NULL;
|