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[81.185.169.240]) by smtp.gmail.com with ESMTPSA id r11sm60497627wre.14.2019.07.24.23.19.52 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 24 Jul 2019 23:19:53 -0700 (PDT) Subject: Re: [PATCH 4.4 stable net] net: tcp: Fix use-after-free in tcp_write_xmit To: maowenan , Eric Dumazet , davem@davemloft.net, gregkh@linuxfoundation.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org References: <20190724091715.137033-1-maowenan@huawei.com> <2e09f4d1-8a47-27e9-60f9-63d3b19a98ec@gmail.com> <13ffa2fe-d064-9786-bc52-e4281d26ed1d@huawei.com> <44f0ba0d-fd19-d44b-9c5c-686e2f8ef988@gmail.com> <9a8d6a5a-9a9d-9cb5-caa9-5c12ba04a43c@huawei.com> From: Eric Dumazet Message-ID: <510109e3-101f-517c-22b4-921432f04fe5@gmail.com> Date: Thu, 25 Jul 2019 08:19:52 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.7.2 MIME-Version: 1.0 In-Reply-To: <9a8d6a5a-9a9d-9cb5-caa9-5c12ba04a43c@huawei.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On 7/25/19 6:29 AM, maowenan wrote: > >>>>> Syzkaller reproducer(): >>>>> r0 = socket$packet(0x11, 0x3, 0x300) >>>>> r1 = socket$inet_tcp(0x2, 0x1, 0x0) >>>>> bind$inet(r1, &(0x7f0000000300)={0x2, 0x4e21, @multicast1}, 0x10) >>>>> connect$inet(r1, &(0x7f0000000140)={0x2, 0x1000004e21, @loopback}, 0x10) >>>>> recvmmsg(r1, &(0x7f0000001e40)=[{{0x0, 0x0, &(0x7f0000000100)=[{&(0x7f00000005c0)=""/88, 0x58}], 0x1}}], 0x1, 0x40000000, 0x0) >>>>> sendto$inet(r1, &(0x7f0000000000)="e2f7ad5b661c761edf", 0x9, 0x8080, 0x0, 0x0) >>>>> r2 = fcntl$dupfd(r1, 0x0, r0) >>>>> connect$unix(r2, &(0x7f00000001c0)=@file={0x0, './file0\x00'}, 0x6e) >>>>> >> >> It does call tcp_disconnect(), by one of the connect() call. > > yes, __inet_stream_connect will call tcp_disconnect when sa_family == AF_UNSPEC, in c repro if it > passes sa_family with AF_INET it won't call disconnect, and then sk_send_head won't be NULL when tcp_connect. > Look again at the Syzkaller reproducer() It definitely uses tcp_disconnect() Do not be fooled by connect$unix(), this is a connect() call really, with AF_UNSPEC