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 A617B40681A; Thu, 27 Aug 2026 10:38:46 +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=1787827127; cv=none; b=ba12gvsJ5iWWl8Y45cCxOG1eNDcokuNdgzCNcDKKt3wb0DSOnBt1KNWLpAqucN+hp1P6xh59UEl+Zpln6Zizg7UOGq3PQzqebS7/E1W7CsNf+idODFNRBrPpVZGuHcm/a0gOH5Zt8LP2uGpuAD08+ovnDkkap5mpQnhsdXrJv5Y= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787827127; c=relaxed/simple; bh=kpzBoAMi5QggTL5lNB84wb6f/X4wKnX7vzY1aZ287bo=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=i/pt7f34luX/+sQj0M1C7G6pyMP6wzmyJHS/sXflcklkguyz3LzjqDumN+kwb30dqZ+PNHGt7TPAVutVfED5CWGUxwgLxaqRs9T6ezcpn147hG+wMNznBZOOA5xzz/k34EwpxcGYtbRyZpnaemPjGkEHM/h281Y3cGIigrba+1U= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=fBNy4Mrn; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="fBNy4Mrn" Received: by smtp.kernel.org (Postfix) with ESMTPSA id A2D631F000E9; Thu, 27 Aug 2026 10:38:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1787827126; bh=r6z877gxLUjF1he0Whhgpdx8cqepvMD7a1r258OVDAE=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=fBNy4MrnnA1ynQhVv3YdZW09m0BES4DXEHnrrtkkj20FSFVf3vTTo08Aq4AuEiX0N mMOVetoPjV0ckoGv/vYgvmmesyYdGTORHIn5KeKPRk0ThB1mY8OLDZ4CybGmABo/U/ ih0+HyCMqtlKdVq7Xi1iaA/SlyQvD/vAZu+JayCy/K7JWAXRnE6n2QxxSF6uKwj2E+ NsPX09H4275jyHceu1ob6tDUXi2JFNkgIWNoNkjK4xW56crkBX9NbNwOgp/7uMypP7 8KICB0UykoMqXnGzWxMIsgPSz50ZNVzPfdOOoSocIq5fVjhyHtdYQ5xWlaEzszIW1c 9Jg/HFEpbxGGA== Message-ID: <1db6cf46-c3cf-49e2-ad97-752afdd78c00@kernel.org> Date: Thu, 27 Aug 2026 12:38:36 +0200 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Beta Subject: Re: [PATCH net v2 1/2] tcp: fix use-after-free in do_tcp_getsockopt(TCP_CONGESTION) To: "Cen Zhang (Microsoft)" Cc: kuniyu@google.com, horms@kernel.org, martineau@kernel.org, geliang@kernel.org, yhs@fb.com, kafai@fb.com, andriin@fb.com, ast@kernel.org, netdev@vger.kernel.org, mptcp@lists.linux.dev, bpf@vger.kernel.org, linux-kernel@vger.kernel.org, AutonomousCodeSecurity@microsoft.com, xmei5@asu.edu, tgopinath@linux.microsoft.com, kys@microsoft.com, stable@vger.kernel.org, edumazet@google.com, ncardwell@google.com, davem@davemloft.net, kuba@kernel.org, pabeni@redhat.com References: <20260826171344.4133-1-blbllhy@gmail.com> <20260826171344.4133-2-blbllhy@gmail.com> From: Matthieu Baerts Content-Language: fr Autocrypt: addr=matttbe@kernel.org; keydata= xsFNBFXj+ekBEADxVr99p2guPcqHFeI/JcFxls6KibzyZD5TQTyfuYlzEp7C7A9swoK5iCvf YBNdx5Xl74NLSgx6y/1NiMQGuKeu+2BmtnkiGxBNanfXcnl4L4Lzz+iXBvvbtCbynnnqDDqU c7SPFMpMesgpcu1xFt0F6bcxE+0ojRtSCZ5HDElKlHJNYtD1uwY4UYVGWUGCF/+cY1YLmtfb WdNb/SFo+Mp0HItfBC12qtDIXYvbfNUGVnA5jXeWMEyYhSNktLnpDL2gBUCsdbkov5VjiOX7 CRTkX0UgNWRjyFZwThaZADEvAOo12M5uSBk7h07yJ97gqvBtcx45IsJwfUJE4hy8qZqsA62A nTRflBvp647IXAiCcwWsEgE5AXKwA3aL6dcpVR17JXJ6nwHHnslVi8WesiqzUI9sbO/hXeXw TDSB+YhErbNOxvHqCzZEnGAAFf6ges26fRVyuU119AzO40sjdLV0l6LE7GshddyazWZf0iac nEhX9NKxGnuhMu5SXmo2poIQttJuYAvTVUNwQVEx/0yY5xmiuyqvXa+XT7NKJkOZSiAPlNt6 VffjgOP62S7M9wDShUghN3F7CPOrrRsOHWO/l6I/qJdUMW+MHSFYPfYiFXoLUZyPvNVCYSgs 3oQaFhHapq1f345XBtfG3fOYp1K2wTXd4ThFraTLl8PHxCn4ywARAQABzSRNYXR0aGlldSBC YWVydHMgPG1hdHR0YmVAa2VybmVsLm9yZz7CwZEEEwEIADsCGwMFCwkIBwIGFQoJCAsCBBYC AwECHgECF4AWIQToy4X3aHcFem4n93r2t4JPQmmgcwUCZUDpDAIZAQAKCRD2t4JPQmmgcz33 EACjROM3nj9FGclR5AlyPUbAq/txEX7E0EFQCDtdLPrjBcLAoaYJIQUV8IDCcPjZMJy2ADp7 /zSwYba2rE2C9vRgjXZJNt21mySvKnnkPbNQGkNRl3TZAinO1Ddq3fp2c/GmYaW1NWFSfOmw MvB5CJaN0UK5l0/drnaA6Hxsu62V5UnpvxWgexqDuo0wfpEeP1PEqMNzyiVPvJ8bJxgM8qoC cpXLp1Rq/jq7pbUycY8GeYw2j+FVZJHlhL0w0Zm9CFHThHxRAm1tsIPc+oTorx7haXP+nN0J iqBXVAxLK2KxrHtMygim50xk2QpUotWYfZpRRv8dMygEPIB3f1Vi5JMwP4M47NZNdpqVkHrm jvcNuLfDgf/vqUvuXs2eA2/BkIHcOuAAbsvreX1WX1rTHmx5ud3OhsWQQRVL2rt+0p1DpROI 3Ob8F78W5rKr4HYvjX2Inpy3WahAm7FzUY184OyfPO/2zadKCqg8n01mWA9PXxs84bFEV2mP VzC5j6K8U3RNA6cb9bpE5bzXut6T2gxj6j+7TsgMQFhbyH/tZgpDjWvAiPZHb3sV29t8XaOF BwzqiI2AEkiWMySiHwCCMsIH9WUH7r7vpwROko89Tk+InpEbiphPjd7qAkyJ+tNIEWd1+MlX ZPtOaFLVHhLQ3PLFLkrU3+Yi3tXqpvLE3gO3LM7BTQRV4/npARAA5+u/Sx1n9anIqcgHpA7l 5SUCP1e/qF7n5DK8LiM10gYglgY0XHOBi0S7vHppH8hrtpizx+7t5DBdPJgVtR6SilyK0/mp 9nWHDhc9rwU3KmHYgFFsnX58eEmZxz2qsIY8juFor5r7kpcM5dRR9aB+HjlOOJJgyDxcJTwM 1ey4L/79P72wuXRhMibN14SX6TZzf+/XIOrM6TsULVJEIv1+NdczQbs6pBTpEK/G2apME7vf mjTsZU26Ezn+LDMX16lHTmIJi7Hlh7eifCGGM+g/AlDV6aWKFS+sBbwy+YoS0Zc3Yz8zrdbi Kzn3kbKd+99//mysSVsHaekQYyVvO0KD2KPKBs1S/ImrBb6XecqxGy/y/3HWHdngGEY2v2IP Qox7mAPznyKyXEfG+0rrVseZSEssKmY01IsgwwbmN9ZcqUKYNhjv67WMX7tNwiVbSrGLZoqf Xlgw4aAdnIMQyTW8nE6hH/Iwqay4S2str4HZtWwyWLitk7N+e+vxuK5qto4AxtB7VdimvKUs x6kQO5F3YWcC3vCXCgPwyV8133+fIR2L81R1L1q3swaEuh95vWj6iskxeNWSTyFAVKYYVskG V+OTtB71P1XCnb6AJCW9cKpC25+zxQqD2Zy0dK3u2RuKErajKBa/YWzuSaKAOkneFxG3LJIv Hl7iqPF+JDCjB5sAEQEAAcLBXwQYAQIACQUCVeP56QIbDAAKCRD2t4JPQmmgc5VnD/9YgbCr HR1FbMbm7td54UrYvZV/i7m3dIQNXK2e+Cbv5PXf19ce3XluaE+wA8D+vnIW5mbAAiojt3Mb 6p0WJS3QzbObzHNgAp3zy/L4lXwc6WW5vnpWAzqXFHP8D9PTpqvBALbXqL06smP47JqbyQxj Xf7D2rrPeIqbYmVY9da1KzMOVf3gReazYa89zZSdVkMojfWsbq05zwYU+SCWS3NiyF6QghbW voxbFwX1i/0xRwJiX9NNbRj1huVKQuS4W7rbWA87TrVQPXUAdkyd7FRYICNW+0gddysIwPoa KrLfx3Ba6Rpx0JznbrVOtXlihjl4KV8mtOPjYDY9u+8x412xXnlGl6AC4HLu2F3ECkamY4G6 UxejX+E6vW6Xe4n7H+rEX5UFgPRdYkS1TA/X3nMen9bouxNsvIJv7C6adZmMHqu/2azX7S7I vrxxySzOw9GxjoVTuzWMKWpDGP8n71IFeOot8JuPZtJ8omz+DZel+WCNZMVdVNLPOd5frqOv mpz0VhFAlNTjU1Vy0CnuxX3AM51J8dpdNyG0S8rADh6C8AKCDOfUstpq28/6oTaQv7QZdge0 JY6dglzGKnCi/zsmp2+1w559frz4+IC7j/igvJGX4KDDKUs0mlld8J2u2sBXv7CGxdzQoHaz lzVbFe7fduHbABmYz9cefQpO7wDE/Q== Organization: NGI0 Core In-Reply-To: <20260826171344.4133-2-blbllhy@gmail.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Hi Cen, On 26/08/2026 19:13, Cen Zhang (Microsoft) wrote: > From: "Cen Zhang (Microsoft Security FORGE Labs)" > > do_tcp_getsockopt() reads icsk->icsk_ca_ops->name without holding > rcu_read_lock(). Since commit 0baf26b0fcd7 ("bpf: tcp: Support > tcp_congestion_ops in bpf"), icsk_ca_ops can point to dynamically > allocated BPF struct_ops memory that may be freed concurrently via > setsockopt(TCP_CONGESTION), leading to a use-after-free. > > BUG: KASAN: slab-use-after-free in _copy_to_user+0x37/0x60 > Read of size 16 at addr ffff888013505260 by task exploit/149 > _copy_to_user+0x37/0x60 > do_tcp_getsockopt+0x158a/0x2460 (net/ipv4/tcp.c:4585) > tcp_getsockopt+0x91/0xf0 > __sys_getsockopt+0xf7/0x170 > > Fix this by holding rcu_read_lock() around the ca_ops->name access, > using READ_ONCE() to load icsk_ca_ops, and copying the name to a > stack buffer before releasing the lock. Also annotate every explicit > icsk_ca_ops store with WRITE_ONCE() to fix the accompanying KCSAN > data-race issue. (...) > diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c > index b4237d0e994d..4918f48ba76d 100644 > --- a/net/ipv4/tcp.c > +++ b/net/ipv4/tcp.c > @@ -4577,16 +4577,24 @@ int do_tcp_getsockopt(struct sock *sk, int level, > val = !inet_csk_in_pingpong_mode(sk); > break; > > - case TCP_CONGESTION: > + case TCP_CONGESTION: { > + char ca_name[TCP_CA_NAME_MAX] = {}; > + > if (copy_from_sockptr(&len, optlen, sizeof(int))) > return -EFAULT; > len = min_t(unsigned int, len, TCP_CA_NAME_MAX); > if (copy_to_sockptr(optlen, &len, sizeof(int))) > return -EFAULT; > - if (copy_to_sockptr(optval, icsk->icsk_ca_ops->name, len)) > + > + rcu_read_lock(); > + ca_ops = READ_ONCE(icsk->icsk_ca_ops); It looks like you (or your assistant) forgot to declare ca_ops: const struct tcp_congestion_ops *ca_ops; Also, I *guess* a 'rcu_read_lock' is needed in mptcp_ca_reset() from net/mptcp/protocol.c, above the modification you did, to get the name, no? Apart from that, the modifications look good to me. Cheers, Matt -- Sponsored by the NGI0 Core fund.