linux-kernel - [PATCH 3.18 04/29] 9p/virtio: fix off-by-one error in sg list bounds check

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Date:   Fri,  7 Sep 2018 23:10:25 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Yiwen Jiang <jiangyiwen@...wei.com>,
        Dan Carpenter <dan.carpenter@...cle.com>,
        Jun Piao <piaojun@...wei.com>,
        Dominique Martinet <dominique.martinet@....fr>
Subject: [PATCH 3.18 04/29] 9p/virtio: fix off-by-one error in sg list bounds check

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

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

From: jiangyiwen <jiangyiwen@...wei.com>

commit 23cba9cbde0bba05d772b335fe5f66aa82b9ad19 upstream.

Because the value of limit is VIRTQUEUE_NUM, if index is equal to
limit, it will cause sg array out of bounds, so correct the judgement
of BUG_ON.

Link: http://lkml.kernel.org/r/5B63D5F6.6080109@huawei.com
Signed-off-by: Yiwen Jiang <jiangyiwen@...wei.com>
Reported-By: Dan Carpenter <dan.carpenter@...cle.com>
Acked-by: Jun Piao <piaojun@...wei.com>
Cc: stable@...r.kernel.org
Signed-off-by: Dominique Martinet <dominique.martinet@....fr>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 net/9p/trans_virtio.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/net/9p/trans_virtio.c
+++ b/net/9p/trans_virtio.c
@@ -192,7 +192,7 @@ static int pack_sg_list(struct scatterli
 		s = rest_of_page(data);
 		if (s > count)
 			s = count;
-		BUG_ON(index > limit);
+		BUG_ON(index >= limit);
 		/* Make sure we don't terminate early. */
 		sg_unmark_end(&sg[index]);
 		sg_set_buf(&sg[index++], data, s);
@@ -238,6 +238,7 @@ pack_sg_list_p(struct scatterlist *sg, i
 		s = rest_of_page(data);
 		if (s > count)
 			s = count;
+		BUG_ON(index >= limit);
 		/* Make sure we don't terminate early. */
 		sg_unmark_end(&sg[index]);
 		sg_set_page(&sg[index++], pdata[i++], s, data_off);