diff options
authorAl Viro <>2017-02-19 07:15:27 +0000
committerLinus Torvalds <>2017-02-19 09:54:31 -0800
commit137d01df511b3afe1f05499aea05f3bafc0fb221 (patch)
parentfd3fc0b4d7305fa7246622dcc0dec69c42443f45 (diff)
Fix missing sanity check in /dev/sg
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 <> Cc: Signed-off-by: Linus Torvalds <>
1 files changed, 4 insertions, 0 deletions
diff --git a/drivers/scsi/sg.c b/drivers/scsi/sg.c
index dbe5b4b95df0..121de0aaa6ad 100644
--- a/drivers/scsi/sg.c
+++ b/drivers/scsi/sg.c
@@ -1753,6 +1753,10 @@ sg_start_req(Sg_request *srp, unsigned char *cmd)
return res;
iov_iter_truncate(&i, hp->dxfer_len);
+ if (!iov_iter_count(&i)) {
+ kfree(iov);
+ return -EINVAL;
+ }
res = blk_rq_map_user_iov(q, rq, md, &i, GFP_ATOMIC);