From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 9A7FF19049B; Thu, 2 Jul 2026 16:38:39 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783010320; cv=none; b=gJfXJpoPi0jMY4w9/3gBEy7aTsl0yZFmEkrjntH4JKBgbcv+y/pMaN1oBsKIZvh6DoYkbsld7YPD/vyeaT8OUlG+u6yOngFv280UThNFMrDF1TlaqqvGpZ5Hu16Cgh4PpZhQdSIIfZFGS0IVMhZxAQf/dLgVGAWnI8T3BEJ0L4s= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783010320; c=relaxed/simple; bh=kP3MDwXjF8rJ8CSS6I1009rImumTGg1BcZJyC8cppjI=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=o9x/RBlQ7wDyTWPV3B7ChqP/0IzVW+BpIb1O46w9GN2p6ksXYRuBPLA0l+mfOouGKoq8cF7cMCNSXjqHigqO+oBbQ6tkvQy6+w9Kthjlsz/Af2hDjLQF7oHbh81ASi3kuhCW4pS/fgVEbA13JgsOYPPbCi6hzWj/j8028JoVoKg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=SuO51oit; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="SuO51oit" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 15A931F000E9; Thu, 2 Jul 2026 16:38:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1783010319; bh=sqb5RYmoHD6RJ7GrYW5s2oIva1U2WXHCmfnD4+AtLFk=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=SuO51oitOi6qPe8qhahTClJPU3VbjU4PqU0d4h4K7yZvH/e6dLPz3v9kjq+tkyb6g 6VwEgA0j0xtZ6XGeMtGwBoUrC9v4Y6BeN8+UOOiUgurgQDnR2MVBwv+2HzxxO8CIPm b9+t3oovr8cTtjFoEH3f+ovFNwC3dcUWPssT8Ps0= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Sebastian Andrzej Siewior , Willem de Bruijn , Jason Xing , Eric Dumazet , Paolo Abeni , Heiko Stuebner , Sasha Levin Subject: [PATCH 6.12 020/204] net: Drop the lock in skb_may_tx_timestamp() Date: Thu, 2 Jul 2026 18:17:57 +0200 Message-ID: <20260702155119.088954900@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260702155118.667618796@linuxfoundation.org> References: <20260702155118.667618796@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.12-stable review patch. If anyone has any objections, please let me know. ------------------ From: Sebastian Andrzej Siewior [ Upstream commit 983512f3a87fd8dc4c94dfa6b596b6e57df5aad7 ] skb_may_tx_timestamp() may acquire sock::sk_callback_lock. The lock must not be taken in IRQ context, only softirq is okay. A few drivers receive the timestamp via a dedicated interrupt and complete the TX timestamp from that handler. This will lead to a deadlock if the lock is already write-locked on the same CPU. Taking the lock can be avoided. The socket (pointed by the skb) will remain valid until the skb is released. The ->sk_socket and ->file member will be set to NULL once the user closes the socket which may happen before the timestamp arrives. If we happen to observe the pointer while the socket is closing but before the pointer is set to NULL then we may use it because both pointer (and the file's cred member) are RCU freed. Drop the lock. Use READ_ONCE() to obtain the individual pointer. Add a matching WRITE_ONCE() where the pointer are cleared. Link: https://lore.kernel.org/all/20260205145104.iWinkXHv@linutronix.de Fixes: b245be1f4db1a ("net-timestamp: no-payload only sysctl") Signed-off-by: Sebastian Andrzej Siewior Reviewed-by: Willem de Bruijn Reviewed-by: Jason Xing Reviewed-by: Eric Dumazet Link: https://patch.msgid.link/20260220183858.N4ERjFW6@linutronix.de Signed-off-by: Paolo Abeni [adapted sk_set_socket() in include/net/sock.h to fix the conflict from not having commit 5d6b58c932ec ("net: lockless sock_i_ino()") and the additional previous changes required by it. It comes down to just now having the lines of if (sock) { WRITE_ONCE(sk->sk_uid, SOCK_INODE(sock)->i_uid); WRITE_ONCE(sk->sk_ino, SOCK_INODE(sock)->i_ino); } below the changed line. I've tested this on a device running an nfs-root and did some additional network stress-testing.] Signed-off-by: Heiko Stuebner Signed-off-by: Sasha Levin --- include/net/sock.h | 2 +- net/core/skbuff.c | 23 ++++++++++++++++++----- net/socket.c | 2 +- 3 files changed, 20 insertions(+), 7 deletions(-) diff --git a/include/net/sock.h b/include/net/sock.h index 0d77a87929f938..dffbaaa7fe493d 100644 --- a/include/net/sock.h +++ b/include/net/sock.h @@ -2040,7 +2040,7 @@ static inline int sk_rx_queue_get(const struct sock *sk) static inline void sk_set_socket(struct sock *sk, struct socket *sock) { - sk->sk_socket = sock; + WRITE_ONCE(sk->sk_socket, sock); } static inline wait_queue_head_t *sk_sleep(struct sock *sk) diff --git a/net/core/skbuff.c b/net/core/skbuff.c index 4be699bd3a17f7..fede3aa3ddbc10 100644 --- a/net/core/skbuff.c +++ b/net/core/skbuff.c @@ -5525,15 +5525,28 @@ static void __skb_complete_tx_timestamp(struct sk_buff *skb, static bool skb_may_tx_timestamp(struct sock *sk, bool tsonly) { - bool ret; + struct socket *sock; + struct file *file; + bool ret = false; if (likely(READ_ONCE(sysctl_tstamp_allow_data) || tsonly)) return true; - read_lock_bh(&sk->sk_callback_lock); - ret = sk->sk_socket && sk->sk_socket->file && - file_ns_capable(sk->sk_socket->file, &init_user_ns, CAP_NET_RAW); - read_unlock_bh(&sk->sk_callback_lock); + /* The sk pointer remains valid as long as the skb is. The sk_socket and + * file pointer may become NULL if the socket is closed. Both structures + * (including file->cred) are RCU freed which means they can be accessed + * within a RCU read section. + */ + rcu_read_lock(); + sock = READ_ONCE(sk->sk_socket); + if (!sock) + goto out; + file = READ_ONCE(sock->file); + if (!file) + goto out; + ret = file_ns_capable(file, &init_user_ns, CAP_NET_RAW); +out: + rcu_read_unlock(); return ret; } diff --git a/net/socket.c b/net/socket.c index 5c5dd9f6605a94..723bc3a1ba5cdd 100644 --- a/net/socket.c +++ b/net/socket.c @@ -652,7 +652,7 @@ static void __sock_release(struct socket *sock, struct inode *inode) iput(SOCK_INODE(sock)); return; } - sock->file = NULL; + WRITE_ONCE(sock->file, NULL); } /** -- 2.53.0