[lkml]   [2017]   [Mar]   [10]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
Patch in this message
Subject[PATCH 3.2 154/199] Fix missing sanity check in /dev/sg
3.2.87-rc1 review patch.  If anyone has any objections, please let me know.


From: Al Viro <>

commit 137d01df511b3afe1f05499aea05f3bafc0fb221 upstream.

What happens is that a write to /dev/sg is given a request with non-zero
->iovec_count combined with zero ->dxfer_len. Or with ->dxferp pointing
to an array full of empty iovecs.

Having write permission to /dev/sg shouldn't be equivalent to the
ability to trigger BUG_ON() while holding spinlocks...

Found by Dmitry Vyukov and syzkaller.

[ The BUG_ON() got changed to a WARN_ON_ONCE(), but this fixes the
underlying issue. - Linus ]

Signed-off-by: Al Viro <>
Reported-by: Dmitry Vyukov <>
Reviewed-by: Christoph Hellwig <>
Signed-off-by: Linus Torvalds <>
[bwh: Backported to 3.2: we're not using iov_iter, but can check the
byte length after truncation]
Signed-off-by: Ben Hutchings <>
drivers/scsi/sg.c | 4 ++++
1 file changed, 4 insertions(+)

--- a/drivers/scsi/sg.c
+++ b/drivers/scsi/sg.c
@@ -1710,6 +1710,10 @@ static int sg_start_req(Sg_request *srp,
iov_count = iov_shorten(iov, iov_count, hp->dxfer_len);
len = hp->dxfer_len;
+ if (len == 0) {
+ kfree(iov);
+ return -EINVAL;
+ }

res = blk_rq_map_user_iov(q, rq, md, (struct sg_iovec *)iov,
 \ /
  Last update: 2017-03-10 13:09    [W:0.505 / U:0.040 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site