From: Martin KaFai Lau kafai@fb.com
[ Upstream commit 8c7138b33e5c690c308b2a7085f6313fdcb3f616 ]
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: a4298e4522d6 ("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 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- net/core/sock.c | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-)
--- a/net/core/sock.c +++ b/net/core/sock.c @@ -1561,8 +1561,6 @@ static void __sk_destruct(struct rcu_hea 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);
@@ -1585,7 +1583,14 @@ static void __sk_destruct(struct rcu_hea
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);