linux-kernel - [PATCH net] macvtap: fix recovery from gup errors

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Message-ID: <20130623142658.GA21141@redhat.com>
Date:	Sun, 23 Jun 2013 17:26:58 +0300
From:	"Michael S. Tsirkin" <mst@...hat.com>
To:	linux-kernel@...r.kernel.org
Cc:	"David S. Miller" <davem@...emloft.net>,
	Jason Wang <jasowang@...hat.com>,
	Eric Dumazet <edumazet@...gle.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	netdev@...r.kernel.org, Brad Hubbard <bhubbard@...hat.com>
Subject: [PATCH net] macvtap: fix recovery from gup errors

get user pages might fail partially in macvtap zero copy
mode. To recover we need to put all pages that we got,
but code used a wrong index resulting in double-free
errors.

Reported-by: Brad Hubbard <bhubbard@...hat.com>
Signed-off-by: Michael S. Tsirkin <mst@...hat.com>
---

Same as the tun patch really. Also stable material.

 drivers/net/macvtap.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/net/macvtap.c b/drivers/net/macvtap.c
index 59e9605..4ddd108 100644
--- a/drivers/net/macvtap.c
+++ b/drivers/net/macvtap.c
@@ -524,8 +524,9 @@ static int zerocopy_sg_from_iovec(struct sk_buff *skb, const struct iovec *from,
 			return -EMSGSIZE;
 		num_pages = get_user_pages_fast(base, size, 0, &page[i]);
 		if (num_pages != size) {
-			for (i = 0; i < num_pages; i++)
-				put_page(page[i]);
+			int j;
+			for (j = 0; j < num_pages; j++)
+				put_page(page[i + j]);
 			return -EFAULT;
 		}
 		truesize = size * PAGE_SIZE;
-- 
MST
--
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