From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-oo1-f71.google.com (mail-oo1-f71.google.com [209.85.161.71]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 53EBB40DFC1 for ; Thu, 2 Apr 2026 02:16:52 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.161.71 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1775096213; cv=none; b=oatLsxblJO67lzy7GYq81Ehqfc7Ok0n9eurb26CFSNqv32sPRdU6Fy1vnWzRX+eiMQ1CUMvj1B19oVkISuBRAisPJ3lPmM1RCNWQlPo9OMoMR1Yk8urELZ07p6mhej1UsMcvIoYFqyaeyeKQTvc0RMtiAOaSAB3NrjEPukfxuS4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1775096213; c=relaxed/simple; bh=Ot17u0h7I6wEIs9wJQ2Vj/x7UijCiXmvimwbWMYN/u0=; h=MIME-Version:Date:In-Reply-To:Message-ID:Subject:From:To: Content-Type; b=QXgbBkE1QgPh1cXt8sVeu5x78bvZMYaESKXg6RgZiorZgq1dAXYSxE/l+0E5/U/7mwiVgsXBa09VhQm6HhlOlZOxtvsHaCzc9e+v7sltaTvTgX8EnTR/WRdhJCE3ydKIXrU/gWzdJngqjfKc+JEK1suuOlIlwSJjWvLmURMcFyo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=fail (p=none dis=none) header.from=syzkaller.appspotmail.com; spf=pass smtp.mailfrom=M3KW2WVRGUFZ5GODRSRYTGD7.apphosting.bounces.google.com; arc=none smtp.client-ip=209.85.161.71 Authentication-Results: smtp.subspace.kernel.org; dmarc=fail (p=none dis=none) header.from=syzkaller.appspotmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=M3KW2WVRGUFZ5GODRSRYTGD7.apphosting.bounces.google.com Received: by mail-oo1-f71.google.com with SMTP id 006d021491bc7-67df4623e1bso1871608eaf.0 for ; Wed, 01 Apr 2026 19:16:52 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1775096211; x=1775701011; h=to:from:subject:message-id:in-reply-to:date:mime-version :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=MUP6gxDOKcy8AjaIQK57yH9QBpYALZkxvmTB6yWirhM=; b=IPOFnXUtJaaA87vSM3sie18ypuH/NZB7aJnaoAcV+jW/lBS2NrQGVT4abzrbN40U5x UWgpoJBEMcqbOjmRAAyc8H5ENRLxd0R5NEyVaW663YAwK3nHBvEBQLBLhwjyZyrXTevW gssdguBciBrnIM/Zs7h3TXq4oCdaaVIFEyl32vzR57e8UoXZnVkWcBRV+33zMhBA5Jgz 14qEGVRyqcHNItQY4SWrdeLuLyz3AfKzhKI1CZs4q/3Iw+stJnL4Q8rR1rMYuNWokFNc pc+FFR1RMDXbIQjbKAR5PV3xYg0fLPGKtrct14h1q968GFNPZTJiYStjWbDwqQWAZhog RW6Q== X-Gm-Message-State: AOJu0Ywmi9z/7eboRWvSv5nWKyXFwRLrypJX/mcL1EpVsqEadF/tFeni xAerqXCg5YPttW0OhOPpQiI1WIbKxKFS7n5rrIbCwKK6KBTM0/ban17ofATtUUmn5ah7F+1IwR/ uujXhYYGUK8eTMN5f70cNFUuVIAjO3c9aniW/CqsN29i85UzJx7lsqEPb5PA= Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Received: by 2002:a05:6820:1888:b0:67e:34a0:a3e0 with SMTP id 006d021491bc7-67fabbd4e69mr3370312eaf.8.1775096211379; Wed, 01 Apr 2026 19:16:51 -0700 (PDT) Date: Wed, 01 Apr 2026 19:16:51 -0700 In-Reply-To: <69cdbd12.050a0220.70c3a.0007.GAE@google.com> X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <69cdd193.050a0220.25c253.047a.GAE@google.com> Subject: Forwarded: [PATCH] udp_bpf: fix use-after-free in udp_bpf_recvmsg() From: syzbot To: linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com Content-Type: text/plain; charset="UTF-8" For archival purposes, forwarding an incoming command email to linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com. *** Subject: [PATCH] udp_bpf: fix use-after-free in udp_bpf_recvmsg() Author: kartikey406@gmail.com #syz test: git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next.git main udp_bpf_recvmsg() calls sk_msg_recvmsg() without holding lock_sock(), unlike tcp_bpf_recvmsg() which properly acquires lock_sock() before calling __sk_msg_recvmsg(). This allows concurrent tasks to race inside sk_msg_recvmsg() on the same psock ingress queue, where one task can free msg_rx via kfree_sk_msg() while another task is still reading it via sk_msg_elem(), causing a slab-use-after-free. Fix this by adding lock_sock()/release_sock() pairs around the recvmsg path. Since udp_msg_wait_data() does not release lock_sock() internally before sleeping (unlike tcp_msg_wait_data()), we must release the socket lock manually before calling udp_msg_wait_data() and reacquire it after to avoid a deadlock with the ingress path delivering new data. Reported-by: syzbot+431f9a9e3f5227fbb904@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=431f9a9e3f5227fbb904 Fixes: 1f5be6b3b063 ("udp: Implement udp_bpf_recvmsg() for sockmap") Signed-off-by: Deepanshu Kartikey --- net/ipv4/udp_bpf.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/net/ipv4/udp_bpf.c b/net/ipv4/udp_bpf.c index 9f33b07b1481..5e6d82816103 100644 --- a/net/ipv4/udp_bpf.c +++ b/net/ipv4/udp_bpf.c @@ -74,7 +74,9 @@ static int udp_bpf_recvmsg(struct sock *sk, struct msghdr *msg, size_t len, if (unlikely(!psock)) return sk_udp_recvmsg(sk, msg, len, flags); + lock_sock(sk); if (!psock_has_data(psock)) { + release_sock(sk); ret = sk_udp_recvmsg(sk, msg, len, flags); goto out; } @@ -86,16 +88,20 @@ static int udp_bpf_recvmsg(struct sock *sk, struct msghdr *msg, size_t len, int data; timeo = sock_rcvtimeo(sk, flags & MSG_DONTWAIT); + release_sock(sk); data = udp_msg_wait_data(sk, psock, timeo); + lock_sock(sk); if (data) { if (psock_has_data(psock)) goto msg_bytes_ready; + release_sock(sk); ret = sk_udp_recvmsg(sk, msg, len, flags); goto out; } copied = -EAGAIN; } ret = copied; + release_sock(sk); out: sk_psock_put(sk, psock); return ret; -- 2.43.0