From: Al Viro Date: Sun, 19 Feb 2017 07:15:27 +0000 (+0000) Subject: Fix missing sanity check in /dev/sg X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=137d01df511b3afe1f05499aea05f3bafc0fb221;p=GitHub%2Fmoto-9609%2Fandroid_kernel_motorola_exynos9610.git 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: stable@vger.kernel.org Signed-off-by: Linus Torvalds --- 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); kfree(iov);