From 4f5f648b4f5b008da04dcef644369b58d24ab9b6 Mon Sep 17 00:00:00 2001 From: Al Viro Date: Sun, 19 Feb 2017 07:15:27 +0000 Subject: Fix missing sanity check in /dev/sg [ Upstream commit 137d01df511b3afe1f05499aea05f3bafc0fb221 ] 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: stable@vger.kernel.org Signed-off-by: Linus Torvalds Signed-off-by: Sasha Levin --- drivers/scsi/sg.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/drivers/scsi/sg.c b/drivers/scsi/sg.c index 26bc4e9c7441..0cc067ce5715 100644 --- a/drivers/scsi/sg.c +++ b/drivers/scsi/sg.c @@ -1757,6 +1757,10 @@ 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); kfree(iov); -- cgit v1.2.3