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net: Unpublish sk from sk_reuseport_cb before call_rcu

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The "reuse->sock[]" array is shared by multiple sockets.  The going away
sk must unpublish itself from "reuse->sock[]" before making call_rcu()
call.  However, this unpublish-action is currently done after a grace
period and it may cause use-after-free.

The fix is to move reuseport_detach_sock() to sk_destruct().
Due to the above reason, any socket with sk_reuseport_cb has
to go through the rcu grace period before freeing it.

It is a rather old bug (~3 yrs).  The Fixes tag is not necessary
the right commit but it is the one that introduced the SOCK_RCU_FREE
logic and this fix is depending on it.

Fixes: a4298e4522 ("net: add SOCK_RCU_FREE socket flag")
Cc: Eric Dumazet <eric.dumazet@gmail.com>
Suggested-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Martin KaFai Lau 2019-09-27 16:00:31 -07:00 committed by David S. Miller
parent 0e141f757b
commit 8c7138b33e
1 changed files with 8 additions and 3 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

11
net/core/sock.c
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@ -1700,8 +1700,6 @@ static void __sk_destruct(struct rcu_head *head)
sk_filter_uncharge(sk, filter);
RCU_INIT_POINTER(sk->sk_filter, NULL);
}
if (rcu_access_pointer(sk->sk_reuseport_cb))
reuseport_detach_sock(sk);
sock_disable_timestamp(sk, SK_FLAGS_TIMESTAMP);
@ -1728,7 +1726,14 @@ static void __sk_destruct(struct rcu_head *head)
void sk_destruct(struct sock *sk)
{
if (sock_flag(sk, SOCK_RCU_FREE))
bool use_call_rcu = sock_flag(sk, SOCK_RCU_FREE);
if (rcu_access_pointer(sk->sk_reuseport_cb)) {
reuseport_detach_sock(sk);
use_call_rcu = true;
}
if (use_call_rcu)
call_rcu(&sk->sk_rcu, __sk_destruct);
else
__sk_destruct(&sk->sk_rcu);