| From cf8364f162c53020b0ea09987e0ab308c7c5a5da Mon Sep 17 00:00:00 2001 |
| From: Al Viro <viro@ZenIV.linux.org.uk> |
| Date: Sun, 19 Feb 2017 07:15:27 +0000 |
| Subject: [PATCH] Fix missing sanity check in /dev/sg |
| |
| 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 <viro@zeniv.linux.org.uk> |
| Reported-by: Dmitry Vyukov <dvyukov@google.com> |
| Reviewed-by: Christoph Hellwig <hch@lst.de> |
| Cc: stable@vger.kernel.org |
| Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
| Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com> |
| |
| diff --git a/drivers/scsi/sg.c b/drivers/scsi/sg.c |
| index a1c29b0afb22..dedcff9cabb5 100644 |
| --- a/drivers/scsi/sg.c |
| +++ b/drivers/scsi/sg.c |
| @@ -1763,6 +1763,10 @@ 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); |
| -- |
| 2.12.0 |
| |
