Patchwork [044/106] macvtap: fix recovery from gup errors

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Submitter Luis Henriques
Date July 30, 2013, 9:31 a.m.
Message ID <1375176725-5825-45-git-send-email-luis.henriques@canonical.com>
Download mbox | patch
Permalink /patch/263317/
State New
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Luis Henriques - July 30, 2013, 9:31 a.m.
3.5.7.18 -stable review patch.  If anyone has any objections, please let me know.

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

From: "Michael S. Tsirkin" <mst@redhat.com>

commit 4c7ab054ab4f5d63625508ed6f8a607184cae7c2 upstream.

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@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Acked-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>
---
 drivers/net/macvtap.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

Patch

diff --git a/drivers/net/macvtap.c b/drivers/net/macvtap.c
index 2ee56de..d566234 100644
--- a/drivers/net/macvtap.c
+++ b/drivers/net/macvtap.c
@@ -534,8 +534,10 @@  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;