netdev - [PATCH] sock: fix /proc/net/sockstat underflow in sk_clone

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Message-Id: <20211114060222.3370-1-penguin-kernel@I-love.SAKURA.ne.jp>
Date:   Sun, 14 Nov 2021 15:02:22 +0900
From:   Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
To:     netdev@...r.kernel.org
Cc:     Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
Subject: [PATCH] sock: fix /proc/net/sockstat underflow in sk_clone_lock()

sk_clone_lock() needs to call get_net() and sock_inuse_inc() together, or
socket_seq_show() will underflow when __sk_free() from sk_free() from
sk_free_unlock_clone() is called.

Signed-off-by: Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
---
 net/core/sock.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/net/core/sock.c b/net/core/sock.c
index 8f2b2f2c0e7b..41e91d0f7061 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -2124,8 +2124,10 @@ struct sock *sk_clone_lock(const struct sock *sk, const gfp_t priority)
 	newsk->sk_prot_creator = prot;
 
 	/* SANITY */
-	if (likely(newsk->sk_net_refcnt))
+	if (likely(newsk->sk_net_refcnt)) {
 		get_net(sock_net(newsk));
+		sock_inuse_add(sock_net(newsk), 1);
+	}
 	sk_node_init(&newsk->sk_node);
 	sock_lock_init(newsk);
 	bh_lock_sock(newsk);
@@ -2197,8 +2199,6 @@ struct sock *sk_clone_lock(const struct sock *sk, const gfp_t priority)
 	newsk->sk_err_soft = 0;
 	newsk->sk_priority = 0;
 	newsk->sk_incoming_cpu = raw_smp_processor_id();
-	if (likely(newsk->sk_net_refcnt))
-		sock_inuse_add(sock_net(newsk), 1);
 
 	/* Before updating sk_refcnt, we must commit prior changes to memory
 	 * (Documentation/RCU/rculist_nulls.rst for details)
-- 
2.32.0