netdev - [PATCH net 2/2] macvtap: limit head length of skb allocated

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <1384250577-20330-2-git-send-email-jasowang@redhat.com>
Date:	Tue, 12 Nov 2013 18:02:57 +0800
From:	Jason Wang <jasowang@...hat.com>
To:	davem@...emloft.net, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, mst@...hat.com, stefanha@...hat.com
Cc:	Jason Wang <jasowang@...hat.com>
Subject: [PATCH net 2/2] macvtap: limit head length of skb allocated

We currently use hdr_len as a hint of head length which is advertised by
guest. But when guest advertise a very big value, it can lead to an 64K+
allocating of kmalloc() which has a very high possibility of failure when host
memory is fragmented or under heavy stress. The huge hdr_len also reduce the
effect of zerocopy or even disable if a gso skb is linearized in guest.

To solves those issues, this patch introduces an upper limit (PAGE_SIZE) of the
head, which guarantees an order 0 allocation each time.

Cc: Stefan Hajnoczi <stefanha@...hat.com>
Cc: Michael S. Tsirkin <mst@...hat.com>
Signed-off-by: Jason Wang <jasowang@...hat.com>
---
The patch was needed for stable.
---
 drivers/net/macvtap.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/net/macvtap.c b/drivers/net/macvtap.c
index 9dccb1e..7ee6f9d 100644
--- a/drivers/net/macvtap.c
+++ b/drivers/net/macvtap.c
@@ -523,6 +523,11 @@ static inline struct sk_buff *macvtap_alloc_skb(struct sock *sk, size_t prepad,
 						int noblock, int *err)
 {
 	struct sk_buff *skb;
+	int good_linear = SKB_MAX_HEAD(prepad);
+
+	/* Don't use huge linear part */
+	if (linear > good_linear)
+		linear = good_linear;
 
 	/* Under a page?  Don't bother with paged skb. */
 	if (prepad + len < PAGE_SIZE || !linear)
-- 
1.8.3.2

--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html