| From | Ben Hutchings <> | Date | Fri, 10 Mar 2017 11:46:23 +0000 | Subject | [PATCH 3.16 307/370] Fix missing sanity check in /dev/sg |
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3.16.42-rc1 review patch. If anyone has any objections, please let me know.
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From: Al Viro <viro@ZenIV.linux.org.uk>
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> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> [bwh: Backported to 3.16: we're not using iov_iter, but can check the byte length after truncation] Signed-off-by: Ben Hutchings <ben@decadent.org.uk> --- drivers/scsi/sg.c | 4 ++++ 1 file changed, 4 insertions(+)
--- a/drivers/scsi/sg.c +++ b/drivers/scsi/sg.c @@ -1716,6 +1716,10 @@ 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, iov_count,
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