From: Douglas Gilbert <[email protected]>
3.12-stable review patch. If anyone has any objections, please let me know.
===============
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.
>From what 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 <[email protected]>
Reviewed-by: Ewan Milne <[email protected]>
Signed-off-by: Martin K. Petersen <[email protected]>
Signed-off-by: Jiri Slaby <[email protected]>
---
drivers/scsi/sg.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/drivers/scsi/sg.c b/drivers/scsi/sg.c
index 0be16bf5f0cd..1f65e32db285 100644
--- a/drivers/scsi/sg.c
+++ b/drivers/scsi/sg.c
@@ -633,7 +633,8 @@ sg_write(struct file *filp, const char __user *buf, size_t
count, loff_t * ppos)
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;
--
2.8.1
