From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 C702D481FDF; Sat, 28 Feb 2026 17:40:48 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772300448; cv=none; b=NOZlPL5c2GbhwpWr3j4KqG+iOlvwuBCLDMleOJSkcc3XbT8MTdMO/ZQdHs8Bwhomc59kaoHGvuHp+6esffqJVKzeynXJjeGydGbTvi9KLJsdumIdDC+AKKZb5T/YdL0pDPAOJMkkfq79h5JxWvyx+ZN77orebdkYNc5reyl3vk8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772300448; c=relaxed/simple; bh=WOkoccIId5DHJYPfVCdMPRT4pu4rdCeXh9/NXk9vzHI=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=eS7HTK3dnvAUIFUvXluJzj0/XDS8c7kcmwwZG58YP+GRNoU3DCR2bluZtaEe+HfS6LbCpmXhV2BeddOZlA/h4Wi76kcMW/FG7nTu7fux/y3SgskWu4/GLpQthYDoK85Mc+yuB5SEy505hC2ojw93EE6Qi6+ueCG7OnMLrMEPbe8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=tULBAGzt; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="tULBAGzt" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9724CC19423; Sat, 28 Feb 2026 17:40:47 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1772300448; bh=WOkoccIId5DHJYPfVCdMPRT4pu4rdCeXh9/NXk9vzHI=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=tULBAGztr4Df3fRxinhCgylnYVdGc2/kj/kAMrw77GsKPtIA7Z8KhpRDQ2WeOHGC4 gTFL1tfimJND04ChbYxdOFJSy2p1KII+H1BDKO/R7ld/Sic5sgiF8UYiS7CFQ4j3U5 Zy9n8yJehAzcKV0JCiuHdfIMtIhQjqdaBFXOql903tYxpl6J2bxiBspJC/sv4ezVBM KaS876BoMSPKU/wHq8nSfxlwDpD2M2u5e1/0bshi16y4bGljq33nYrkxf5FAS1KEQV RzCHNpcv7Fkv8F1bYldaBlKZ1nkwaHfgTo7KlG6zTnK76+K5Bqrcr+USJ/Hw034Rzd Tb706/NKXO/PA== From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Sebastian Andrzej Siewior , Willem de Bruijn , Jason Xing , Eric Dumazet , Paolo Abeni , Sasha Levin Subject: [PATCH 6.19 488/844] net: Drop the lock in skb_may_tx_timestamp() Date: Sat, 28 Feb 2026 12:26:41 -0500 Message-ID: <20260228173244.1509663-489-sashal@kernel.org> X-Mailer: git-send-email 2.51.0 In-Reply-To: <20260228173244.1509663-1-sashal@kernel.org> References: <20260228173244.1509663-1-sashal@kernel.org> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit 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 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 aafe8bdb2c0f9..ff65c3a67efa2 100644 --- a/include/net/sock.h +++ b/include/net/sock.h @@ -2089,7 +2089,7 @@ 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); if (sock) { WRITE_ONCE(sk->sk_uid, SOCK_INODE(sock)->i_uid); WRITE_ONCE(sk->sk_ino, SOCK_INODE(sock)->i_ino); diff --git a/net/core/skbuff.c b/net/core/skbuff.c index fa6209f45de9c..79dc6d6900cd3 100644 --- a/net/core/skbuff.c +++ b/net/core/skbuff.c @@ -5555,15 +5555,28 @@ 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(tsonly || READ_ONCE(sock_net(sk)->core.sysctl_tstamp_allow_data))) 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 136b98c54fb37..05952188127f5 100644 --- a/net/socket.c +++ b/net/socket.c @@ -674,7 +674,7 @@ static void __sock_release(struct socket *sock, struct inode *inode) iput(SOCK_INODE(sock)); return; } - sock->file = NULL; + WRITE_ONCE(sock->file, NULL); } /** -- 2.51.0