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| author | Eric Dumazet <eric.dumazet@gmail.com> | 2010-07-26 13:09:16 -0700 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2010-07-26 13:09:16 -0700 |
| commit | 1235f504aaba2ebeabc863fdb3ceac764a317d47 (patch) | |
| tree | 58969a45226b9d35bbfc7ecc3dab2823c117db39 | |
| parent | 7b5e078cf04ea5b8b7ccffaf9a3607097f5c2359 (diff) | |
| download | linux-1235f504aaba2ebeabc863fdb3ceac764a317d47.tar.gz linux-1235f504aaba2ebeabc863fdb3ceac764a317d47.tar.bz2 linux-1235f504aaba2ebeabc863fdb3ceac764a317d47.zip | |
netlink: netlink_recvmsg() fix
commit 1dacc76d0014
(net/compat/wext: send different messages to compat tasks)
introduced a race condition on netlink, in case MSG_PEEK is used.
An skb given by skb_recv_datagram() might be shared, we must copy it
before any modification, or risk fatal corruption.
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
| -rw-r--r-- | net/netlink/af_netlink.c | 22 |
1 files changed, 16 insertions, 6 deletions
diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c index 8648a9922aab..2cbf380377d5 100644 --- a/net/netlink/af_netlink.c +++ b/net/netlink/af_netlink.c @@ -1406,7 +1406,7 @@ static int netlink_recvmsg(struct kiocb *kiocb, struct socket *sock, struct netlink_sock *nlk = nlk_sk(sk); int noblock = flags&MSG_DONTWAIT; size_t copied; - struct sk_buff *skb, *frag __maybe_unused = NULL; + struct sk_buff *skb; int err; if (flags&MSG_OOB) @@ -1441,7 +1441,21 @@ static int netlink_recvmsg(struct kiocb *kiocb, struct socket *sock, kfree_skb(skb); skb = compskb; } else { - frag = skb_shinfo(skb)->frag_list; + /* + * Before setting frag_list to NULL, we must get a + * private copy of skb if shared (because of MSG_PEEK) + */ + if (skb_shared(skb)) { + struct sk_buff *nskb; + + nskb = pskb_copy(skb, GFP_KERNEL); + kfree_skb(skb); + skb = nskb; + err = -ENOMEM; + if (!skb) + goto out; + } + kfree_skb(skb_shinfo(skb)->frag_list); skb_shinfo(skb)->frag_list = NULL; } } @@ -1478,10 +1492,6 @@ static int netlink_recvmsg(struct kiocb *kiocb, struct socket *sock, if (flags & MSG_TRUNC) copied = skb->len; -#ifdef CONFIG_COMPAT_NETLINK_MESSAGES - skb_shinfo(skb)->frag_list = frag; -#endif - skb_free_datagram(sk, skb); if (nlk->cb && atomic_read(&sk->sk_rmem_alloc) <= sk->sk_rcvbuf / 2) |