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Commit fbb1fb4a authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller
Browse files

net: defer call to cgroup_sk_alloc() 



sk_clone_lock() might run while TCP/DCCP listener already vanished.

In order to prevent use after free, it is better to defer cgroup_sk_alloc()
to the point we know both parent and child exist, and from process context.

Fixes: e994b2f0 ("tcp: do not lock listener to process SYN packets")
Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 9f1c2674

kernel/cgroup/cgroup.c

+0 −11
Original line number Diff line number Diff line
@@ -5709,17 +5709,6 @@ void cgroup_sk_alloc(struct sock_cgroup_data *skcd) 
	if (cgroup_sk_alloc_disabled)

		return;



	/* Socket clone path */

	if (skcd->val) {

		/*

		 * We might be cloning a socket which is left in an empty

		 * cgroup and the cgroup might have already been rmdir'd.

		 * Don't use cgroup_get_live().

		 */

		cgroup_get(sock_cgroup_ptr(skcd));

		return;

	}



	rcu_read_lock();



	while (true) {

net/core/sock.c

+1 −2
Original line number Diff line number Diff line
@@ -1680,6 +1680,7 @@ struct sock *sk_clone_lock(const struct sock *sk, const gfp_t priority) 


		/* sk->sk_memcg will be populated at accept() time */

		newsk->sk_memcg = NULL;

		memset(&newsk->sk_cgrp_data, 0, sizeof(newsk->sk_cgrp_data));



		atomic_set(&newsk->sk_drops, 0);

		newsk->sk_send_head	= NULL;
@@ -1718,8 +1719,6 @@ struct sock *sk_clone_lock(const struct sock *sk, const gfp_t priority) 
		newsk->sk_incoming_cpu = raw_smp_processor_id();

		atomic64_set(&newsk->sk_cookie, 0);



		cgroup_sk_alloc(&newsk->sk_cgrp_data);



		/*

		 * Before updating sk_refcnt, we must commit prior changes to memory

		 * (Documentation/RCU/rculist_nulls.txt for details)

net/ipv4/inet_connection_sock.c

+5 −0
Original line number Diff line number Diff line
@@ -26,6 +26,8 @@ 
#include <net/tcp.h>

#include <net/sock_reuseport.h>

#include <net/addrconf.h>

#include <net/cls_cgroup.h>

#include <net/netprio_cgroup.h>



#ifdef INET_CSK_DEBUG

const char inet_csk_timer_bug_msg[] = "inet_csk BUG: unknown timer value\n";
@@ -476,6 +478,9 @@ struct sock *inet_csk_accept(struct sock *sk, int flags, int *err, bool kern) 
		spin_unlock_bh(&queue->fastopenq.lock);

	}

	mem_cgroup_sk_alloc(newsk);

	cgroup_sk_alloc(&newsk->sk_cgrp_data);

	sock_update_classid(&newsk->sk_cgrp_data);

	sock_update_netprioidx(&newsk->sk_cgrp_data);

out:

	release_sock(sk);

	if (req)