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[128.10.127.250]) by smtp.googlemail.com with ESMTPSA id cs10-20020a056638470a00b0039d756fb908sm3547284jab.40.2023.01.18.17.35.43 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 18 Jan 2023 17:35:44 -0800 (PST) From: Sungwoo Kim Cc: daveti@purdue.edu, wuruoyu@me.com, benquike@gmail.com, Sungwoo Kim , Marcel Holtmann , Johan Hedberg , Luiz Augusto von Dentz , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , linux-bluetooth@vger.kernel.org (open list:BLUETOOTH SUBSYSTEM), netdev@vger.kernel.org (open list:NETWORKING [GENERAL]), linux-kernel@vger.kernel.org (open list) Subject: [PATCH] L2CAP: Fix null-ptr-deref in l2cap_sock_set_shutdown_cb Date: Wed, 18 Jan 2023 20:34:05 -0500 Message-Id: <20230119013405.3870506-1-iam@sung-woo.kim> X-Mailer: git-send-email 2.25.1 MIME-Version: 1.0 X-Spam-Status: No, score=-1.4 required=5.0 tests=BAYES_00, FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM,HEADER_FROM_DIFFERENT_DOMAINS, RCVD_IN_DNSWL_NONE,RCVD_IN_MSPIKE_H2,SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net To: unlisted-recipients:; (no To-header on input) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-getmail-retrieved-from-mailbox: =?utf-8?q?INBOX?= X-GMAIL-THRID: =?utf-8?q?1755413877926323450?= X-GMAIL-MSGID: =?utf-8?q?1755413877926323450?= The L2CAP socket shutdown invokes l2cap_sock_destruct without a lock on conn->chan_lock, assigning NULL to chan->data *just before* the l2cap_disconnect_req thread that accesses to chan->data. This patch prevent it by adding a null check for a workaround, instead of fixing a lock. This bug is found by FuzzBT, a modified Syzkaller by Sungwoo Kim(me). Ruoyu Wu(wuruoyu@me.com) and Hui Peng(benquike@gmail.com) has helped the FuzzBT project. Signed-off-by: Sungwoo Kim --- net/bluetooth/l2cap_sock.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff --git a/net/bluetooth/l2cap_sock.c b/net/bluetooth/l2cap_sock.c index ca8f07f35..350c7afdf 100644 --- a/net/bluetooth/l2cap_sock.c +++ b/net/bluetooth/l2cap_sock.c @@ -1681,9 +1681,11 @@ static void l2cap_sock_set_shutdown_cb(struct l2cap_chan *chan) { struct sock *sk = chan->data; - lock_sock(sk); - sk->sk_shutdown = SHUTDOWN_MASK; - release_sock(sk); + if (!sk) { + lock_sock(sk); + sk->sk_shutdown = SHUTDOWN_MASK; + release_sock(sk); + } } static long l2cap_sock_get_sndtimeo_cb(struct l2cap_chan *chan)