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 D6D823AA19B; Wed, 23 Sep 2026 14:22:13 +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=1790173335; cv=none; b=Z1Xrlvs48BK6obe7Tx95ASo++HZlX0szEcnhH60/770xw09EnEBPWNGVfppefknLA62AhItYE1Zv7aeHf3loKoLk8FODuAxhkVDMeMFcIDqgYny5J9HaDJQFpQ5Okz6bNDBO2HcNp0+G6UsscKmAnXzPIfVpdYDsbrcrpDGi9B8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790173335; c=relaxed/simple; bh=Mq57Y13eowkDvg4h2pFbtqkkyz8Dizhg9pF3E0iDGss=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=qTd4d/5SzuCl6YkHkiDQIf+50AJETQuI7u5p5gGdcYyLk67beghhHXuP/2weohES1z5HYje32P3C5AtcxD3Qwk+aRO8GLgPmRx6z7PZlV3nSdysyz0kWCFuwGlK3oWZOcz2ue7aei+D2GECRe1uBoH0F+/XelATSI7HApQmQSxc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=I8khgkiA; 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="I8khgkiA" Received: by smtp.kernel.org (Postfix) with ESMTPSA id E299B1F000FF; Wed, 23 Sep 2026 14:22:12 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1790173333; bh=43Kl0VxwBJWk/qTx9ustmNg51EFt6Sy0279vfUq/Ob8=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=I8khgkiAkWkgwzusyByD2y+RlmVMGqDTNPeS8Me3rD1PLggCRrU4bk+ceUHU50CH3 rvhPb9kTJrSvJCaAXGbnTwyL6v5kzSMFGMOEpZE75T5yVkISph+7tEH4GUQdCfblQA 4EDzOiKHF24Lw5K4UzvMWvkDgtN0u8RM7fUGtEvA= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Jungwoo Lee , Wongi Lee , Eric Dumazet , Simon Horman , Jakub Kicinski , Sasha Levin Subject: [PATCH 7.2 212/438] net: lock the socket in sock_gettstamp() Date: Wed, 23 Sep 2026 16:03:53 +0200 Message-ID: <20260923140650.253571776@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260923140644.756254324@linuxfoundation.org> References: <20260923140644.756254324@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 7.2-stable review patch. If anyone has any objections, please let me know. ------------------ From: Eric Dumazet [ Upstream commit 9ed55f3dbef4f4adfe65eb03b0c35c53229a8490 ] sk->sk_flags must only be changed while holding the socket lock, because sock_set_flag() and sock_reset_flag() use non atomic operations (__set_bit() and __clear_bit()). sock_gettstamp() is one of the last places where a bit of sk->sk_flags is changed from a syscall without owning the socket lock, through sock_enable_timestamp(sk, SOCK_TIMESTAMP). sk_set_memalloc() and sk_clear_memalloc() also change sk->sk_flags without the socket lock, but their callers (nbd, iscsi_tcp, nvme-tcp, sunrpc, wireguard) need a careful audit, this will be addressed in a separate patch. Jungwoo Lee and Wongi Lee reported an UDP socket use-after-free caused by this bug: a SIOCGSTAMPNS_NEW ioctl racing with bind() can cancel the SOCK_RCU_FREE bit that udp_lib_get_port() just set, because both threads perform a read-modify-write on the same word. CPU 0 (bind) CPU 1 (SIOCGSTAMPNS_NEW) -------------------------------- ---------------------------- read sk_flags = F read sk_flags = F compute F | BIT(SOCK_RCU_FREE) compute F | BIT(SOCK_TIMESTAMP) store F | BIT(SOCK_RCU_FREE) sk_add_node_rcu(sk, ...) store F | BIT(SOCK_TIMESTAMP) After the lost update, SOCK_RCU_FREE is clear while the socket is visible to lockless UDP receive lookups. sk_destruct() then frees the socket immediately instead of waiting for a RCU grace period, while the receive path still holds a reference-less pointer to it: BUG: KASAN: slab-use-after-free in ipv4_pktinfo_prepare+0x30/0x410 Read of size 8 at addr ffff888008806610 by task exploit/207 CPU: 0 UID: 1000 PID: 207 Comm: exploit Not tainted 6.12.95+ #1 ipv4_pktinfo_prepare+0x30/0x410 udp_queue_rcv_one_skb+0x51c/0x1180 udp_unicast_rcv_skb+0x109/0x350 ip_protocol_deliver_rcu+0x14b/0x310 ip_local_deliver_finish+0x29d/0x390 ip_local_deliver+0x24d/0x2a0 Only grab the socket lock when SOCK_TIMESTAMP has to be set, to keep the common case lockless. Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Reported-by: Jungwoo Lee Reported-by: Wongi Lee Signed-off-by: Eric Dumazet Reviewed-by: Simon Horman Link: https://patch.msgid.link/20260915043055.3441600-1-edumazet@google.com Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin --- net/core/sock.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/net/core/sock.c b/net/core/sock.c index 1ad41904db25b..5c1a1d1950752 100644 --- a/net/core/sock.c +++ b/net/core/sock.c @@ -3908,7 +3908,14 @@ int sock_gettstamp(struct socket *sock, void __user *userstamp, struct sock *sk = sock->sk; struct timespec64 ts; - sock_enable_timestamp(sk, SOCK_TIMESTAMP); + /* sk->sk_flags must only be changed under the socket lock, + * because sock_set_flag() uses non atomic operations. + */ + if (!sock_flag(sk, SOCK_TIMESTAMP)) { + lock_sock(sk); + sock_enable_timestamp(sk, SOCK_TIMESTAMP); + release_sock(sk); + } ts = ktime_to_timespec64(sock_read_timestamp(sk)); if (ts.tv_sec == -1) return -ENOENT; -- 2.53.0