From fc752f1f43c1c038a2c6ae58cc739ebb5953ccb0 Mon Sep 17 00:00:00 2001 From: "subashab@codeaurora.org" Date: Fri, 23 Jan 2015 22:26:02 +0000 Subject: [PATCH] ping: Fix race in free in receive path An exception is seen in ICMP ping receive path where the skb destructor sock_rfree() tries to access a freed socket. This happens because ping_rcv() releases socket reference with sock_put() and this internally frees up the socket. Later icmp_rcv() will try to free the skb and as part of this, skb destructor is called and which leads to a kernel panic as the socket is freed already in ping_rcv(). -->|exception -007|sk_mem_uncharge -007|sock_rfree -008|skb_release_head_state -009|skb_release_all -009|__kfree_skb -010|kfree_skb -011|icmp_rcv -012|ip_local_deliver_finish Fix this incorrect free by cloning this skb and processing this cloned skb instead. This patch was suggested by Eric Dumazet Signed-off-by: Subash Abhinov Kasiviswanathan Cc: Eric Dumazet Signed-off-by: Eric Dumazet Signed-off-by: David S. Miller --- net/ipv4/ping.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/net/ipv4/ping.c b/net/ipv4/ping.c index c0d82f7..2a3720f 100644 --- a/net/ipv4/ping.c +++ b/net/ipv4/ping.c @@ -966,8 +966,11 @@ bool ping_rcv(struct sk_buff *skb) sk = ping_lookup(net, skb, ntohs(icmph->un.echo.id)); if (sk != NULL) { + struct sk_buff *skb2 = skb_clone(skb, GFP_ATOMIC); + pr_debug("rcv on socket %p\n", sk); - ping_queue_rcv_skb(sk, skb_get(skb)); + if (skb2) + ping_queue_rcv_skb(sk, skb2); sock_put(sk); return true; } -- 2.7.4