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.duma...@gmail.com>
Suggested-by: Eric Dumazet <eric.duma...@gmail.com>
Signed-off-by: Martin KaFai Lau <ka...@fb.com>
---
net/core/sock.c | 11 ++++++++---
1 file changed, 8 insertions(+), 3 deletions(-)
diff --git a/net/core/sock.c b/net/core/sock.c
index 07863edbe6fc..e23ec80a67bf 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -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);
--
2.17.1
