linux-kernel - [PATCH 4.8 38/45] Dont feed anything but regular iovecs to blk_rq_map_user

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Date:   Fri,  9 Dec 2016 17:21:07 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Al Viro <viro@...IV.linux.org.uk>,
        Linus Torvalds <torvalds@...ux-foundation.org>
Subject: [PATCH 4.8 38/45] Dont feed anything but regular iovecs to blk_rq_map_user_iov

4.8-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Linus Torvalds <torvalds@...ux-foundation.org>

commit a0ac402cfcdc904f9772e1762b3fda112dcc56a0 upstream.

In theory we could map other things, but there's a reason that function
is called "user_iov".  Using anything else (like splice can do) just
confuses it.

Reported-and-tested-by: Johannes Thumshirn <jthumshirn@...e.de>
Cc: Al Viro <viro@...IV.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 block/blk-map.c |    4 ++++
 1 file changed, 4 insertions(+)

--- a/block/blk-map.c
+++ b/block/blk-map.c
@@ -118,6 +118,9 @@ int blk_rq_map_user_iov(struct request_q
 	struct iov_iter i;
 	int ret;
 
+	if (!iter_is_iovec(iter))
+		goto fail;
+
 	if (map_data)
 		copy = true;
 	else if (iov_iter_alignment(iter) & align)
@@ -140,6 +143,7 @@ int blk_rq_map_user_iov(struct request_q
 
 unmap_rq:
 	__blk_rq_unmap_user(bio);
+fail:
 	rq->bio = NULL;
 	return -EINVAL;
 }