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

From: Luis Henriques
Date: Tue Jul 30 2013 - 05:33:08 EST -stable review patch. If anyone has any objections, please let me know.


From: "Michael S. Tsirkin" <mst@xxxxxxxxxx>

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

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

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;

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