From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-ot1-f70.google.com (mail-ot1-f70.google.com [209.85.210.70]) (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 BD2952DA74C for ; Thu, 2 Apr 2026 04:28:52 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.210.70 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1775104134; cv=none; b=fMyAp+cdyho1hh9N/JteTRF2woVMQIbCN8yPVqLXiQqmwsHC+hRgTttlvj8rcXbmRf3g7x2YjeCWZ1NsrUQMHp+hLg7vuEnobLb3u5NOIIR7z/Hu97PH/HPVdIauv0jZ/I4UUZpZcjdOo8ynrvduIbKt+ydkQEUrerkMde6GUPI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1775104134; c=relaxed/simple; bh=+KWFVI/d7l+f3MBrmwkMq6H5jNu8YP31kWl+VZdSdbg=; h=MIME-Version:Date:In-Reply-To:Message-ID:Subject:From:To: Content-Type; b=oHHO85VAwgPMrdjxkELkh9crzTFJSKPq3vSuweDqo15fIkCjLJErdTHEhdExdir/h1rOy6bBaPwnSrQd5tcClk+QN3jZYhAUMHS2Sgb/eM2R4y1RAY1gdDHJibLAXlXif0HN5aDzIp3QEXDhaLDkO/3UUoLQoJwQFB85NonAqhE= 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=209.85.210.70 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-ot1-f70.google.com with SMTP id 46e09a7af769-7d7c5b6c1c6so1080278a34.3 for ; Wed, 01 Apr 2026 21:28:52 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1775104131; x=1775708931; 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=Be574CEDJIqu1B6u+r0sXLedhD9VbH9M2Vug3vA/SIo=; b=Umfu2aA/4GJxj8pRxAcss7MRTjhAitf3iKReoE0J5Ry69viWFaKkx/NvRI9s2KGt6I RESHkSvUakY1XK8L2YzGTIx0ISiAOI/EV5eZCusFUzzsbz0X1fxrbw0Enz/u4GYPlppV F401aI/TvH/cddkR1p1rIKSiCP/kPWQhNIfmw2et9ANA1wSo1T1Bcpkh+agjAlrjG4Ft J18iH67s4TIHQ9q+38gBS0Si6eC50t/QbapTm/VDTz/wyRqFWU5778Did88FPpTgsktj rA56JagIDMxaeljv0X+0oMP8nqhkaIFdeBj8yqiZg5TNLeBYh9jTK9fMvUoBtI/TPrwW c3rg== X-Gm-Message-State: AOJu0YxEOg/JzxVac52IAoF2dsKJpmCvFJaOmXyOFVJRzU5y2ROrx7ye 0UbFvec58ymsZsxJ4vnI44863jIOKKGTbnVAgpaaeQVWiRpVA6/jLmb8O8VX01a3yK4OEZs3eog GL2joMv5oBGzU1GTd7ghSTn7C7VlJTsbLGNG51+Cg83Cr9Y+8SrxYz48stEU= Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Received: by 2002:a05:6820:2007:b0:67e:f5:9d70 with SMTP id 006d021491bc7-67fabd142e6mr3169983eaf.67.1775104131737; Wed, 01 Apr 2026 21:28:51 -0700 (PDT) Date: Wed, 01 Apr 2026 21:28:51 -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: <69cdf083.050a0220.182279.0000.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() around the sk_msg_recvmsg() path in udp_bpf_recvmsg(), consistent with tcp_bpf_recvmsg(). Also make udp_msg_wait_data() release lock_sock() before sleeping and reacquire it after waking, so it can be called with the socket lock held, consistent with how tcp_msg_wait_data() uses sk_wait_event() which does the same internally. 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 | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/net/ipv4/udp_bpf.c b/net/ipv4/udp_bpf.c index 9f33b07b1481..f924b255cee6 100644 --- a/net/ipv4/udp_bpf.c +++ b/net/ipv4/udp_bpf.c @@ -50,7 +50,9 @@ static int udp_msg_wait_data(struct sock *sk, struct sk_psock *psock, sk_set_bit(SOCKWQ_ASYNC_WAITDATA, sk); ret = udp_msg_has_data(sk, psock); if (!ret) { + release_sock(sk); wait_woken(&wait, TASK_INTERRUPTIBLE, timeo); + lock_sock(sk); ret = udp_msg_has_data(sk, psock); } sk_clear_bit(SOCKWQ_ASYNC_WAITDATA, sk); @@ -79,6 +81,7 @@ static int udp_bpf_recvmsg(struct sock *sk, struct msghdr *msg, size_t len, goto out; } + lock_sock(sk); msg_bytes_ready: copied = sk_msg_recvmsg(sk, psock, msg, len, flags); if (!copied) { @@ -90,12 +93,14 @@ static int udp_bpf_recvmsg(struct sock *sk, struct msghdr *msg, size_t len, 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