Commit fc752f1f authored by subashab@codeaurora.org's avatar subashab@codeaurora.org Committed by David S. Miller

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: default avatarSubash Abhinov Kasiviswanathan <subashab@codeaurora.org>
Cc: Eric Dumazet <edumazet@google.com>
Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 86f3cddb
...@@ -966,8 +966,11 @@ bool ping_rcv(struct sk_buff *skb) ...@@ -966,8 +966,11 @@ bool ping_rcv(struct sk_buff *skb)
sk = ping_lookup(net, skb, ntohs(icmph->un.echo.id)); sk = ping_lookup(net, skb, ntohs(icmph->un.echo.id));
if (sk != NULL) { if (sk != NULL) {
struct sk_buff *skb2 = skb_clone(skb, GFP_ATOMIC);
pr_debug("rcv on socket %p\n", sk); 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); sock_put(sk);
return true; return true;
} }
......
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