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[144.76.156.219]) by smtp.gmail.com with ESMTPSA id u18-20020a5d6ad2000000b00313e90d1d0dsm8529221wrw.112.2023.06.27.06.25.14 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 27 Jun 2023 06:25:15 -0700 (PDT) From: Matthieu Baerts To: stable@vger.kernel.org, gregkh@linuxfoundation.org Cc: MPTCP Upstream , Paolo Abeni , Christoph Paasch , Matthieu Baerts , Jakub Kicinski Subject: [PATCH 5.15.y] mptcp: fix possible divide by zero in recvmsg() Date: Tue, 27 Jun 2023 15:25:10 +0200 Message-Id: <20230627132510.2265333-1-matthieu.baerts@tessares.net> X-Mailer: git-send-email 2.40.1 In-Reply-To: <2023062346-annoying-sublime-7ac7@gregkh> References: <2023062346-annoying-sublime-7ac7@gregkh> Precedence: bulk X-Mailing-List: mptcp@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=4696; i=matthieu.baerts@tessares.net; h=from:subject; bh=DkbpepONqDKmY96usy8COyoWYlTn2Z5Db2UF7nhNSYk=; b=owEBbQKS/ZANAwAIAfa3gk9CaaBzAcsmYgBkmuM2IVbLFaiVaMAlmqbsl2sUgfVbDL1uBcRoU MVfx9rajMeJAjMEAAEIAB0WIQToy4X3aHcFem4n93r2t4JPQmmgcwUCZJrjNgAKCRD2t4JPQmmg c0hYEADVFJvQcQJtltWqh8+pwNetjUTjfUEyh4eZyDurdpYm6TxV7mCENT3zvQivFvx3ZIpSvcD qa6uoKwv41HSrMOspeQm3iltBURIh4wVHXUYroqeDNbwi3spmTQZWhQSBHE3De2hLLo3zvjdxEt Mq8hmOZH5cIij4XeCeglogj1BK2w06wZ79FJowBbKaHDYTEwztIPPNnJY9+fwNEDRwfQh80clZU x6MkpGgKBePlNUNEEzAPdgYJSBpczpCXxxGDCxObzntN/dD68czz8FiIYWjWaVTL8tXX3lHqoXq 4Gm0rZ0lrlGEV9B+LnwWB3Znv9NbYOws1YN+MtmKUeS3dAScX8nCY77pz5q8Oqv7rKyFxcKMV2E EhJNaamL274rGpTyfBEfv4IUjaLHahP0fU7dHCWMcwkPeO/LKSK02dE8e3SZda/3tDALNd8jKVC WnRCffs+ym7WY/vpF92Ce126uDzMj6VQ4VAUUFpm0fFhG5POFPhdre5rmFMFrhU74eLXiAlbxyx YRJJFNmXE6wttGy9PlgDs80T9XXOuTlX69hOgYUJ2C0FD71kWNIXJlosFCExMosPSHyBwyjaQRH lxl18UYz75wqdhjClYRThmrKpzCxrpcIWJAfiB+3H7Hr82EnUSRHkiTHMEViARu/x8CNXSN8yD3 nwMYx/BTLD/IdqA== X-Developer-Key: i=matthieu.baerts@tessares.net; a=openpgp; fpr=E8CB85F76877057A6E27F77AF6B7824F4269A073 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" From: Paolo Abeni commit 0ad529d9fd2bfa3fc619552a8d2fb2f2ef0bce2e upstream. Christoph reported a divide by zero bug in mptcp_recvmsg(): divide error: 0000 [#1] PREEMPT SMP CPU: 1 PID: 19978 Comm: syz-executor.6 Not tainted 6.4.0-rc2-gffcc7899081b = #20 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.11.0-2.el7 04= /01/2014 RIP: 0010:__tcp_select_window+0x30e/0x420 net/ipv4/tcp_output.c:3018 Code: 11 ff 0f b7 cd c1 e9 0c b8 ff ff ff ff d3 e0 89 c1 f7 d1 01 cb 21 c3 = eb 17 e8 2e 83 11 ff 31 db eb 0e e8 25 83 11 ff 89 d8 99 7c 24 04 29 d= 3 65 48 8b 04 25 28 00 00 00 48 3b 44 24 10 75 60 RSP: 0018:ffffc90000a07a18 EFLAGS: 00010246 RAX: 000000000000ffd7 RBX: 000000000000ffd7 RCX: 0000000000040000 RDX: 0000000000000000 RSI: 000000000003ffff RDI: 0000000000040000 RBP: 000000000000ffd7 R08: ffffffff820cf297 R09: 0000000000000001 R10: 0000000000000000 R11: ffffffff8103d1a0 R12: 0000000000003f00 R13: 0000000000300000 R14: ffff888101cf3540 R15: 0000000000180000 FS: 00007f9af4c09640(0000) GS:ffff88813bd00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000001b33824000 CR3: 000000012f241001 CR4: 0000000000170ee0 Call Trace: __tcp_cleanup_rbuf+0x138/0x1d0 net/ipv4/tcp.c:1611 mptcp_recvmsg+0xcb8/0xdd0 net/mptcp/protocol.c:2034 inet_recvmsg+0x127/0x1f0 net/ipv4/af_inet.c:861 ____sys_recvmsg+0x269/0x2b0 net/socket.c:1019 ___sys_recvmsg+0xe6/0x260 net/socket.c:2764 do_recvmmsg+0x1a5/0x470 net/socket.c:2858 __do_sys_recvmmsg net/socket.c:2937 [inline] __se_sys_recvmmsg net/socket.c:2953 [inline] __x64_sys_recvmmsg+0xa6/0x130 net/socket.c:2953 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x47/0xa0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x72/0xdc RIP: 0033:0x7f9af58fc6a9 Code: 5c c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 = 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff f= f 73 01 c3 48 8b 0d 4f 37 0d 00 f7 d8 64 89 01 48 RSP: 002b:00007f9af4c08cd8 EFLAGS: 00000246 ORIG_RAX: 000000000000012b RAX: ffffffffffffffda RBX: 00000000006bc050 RCX: 00007f9af58fc6a9 RDX: 0000000000000001 RSI: 0000000020000140 RDI: 0000000000000004 RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000f00 R11: 0000000000000246 R12: 00000000006bc05c R13: fffffffffffffea8 R14: 00000000006bc050 R15: 000000000001fe40 mptcp_recvmsg is allowed to release the msk socket lock when blocking, and before re-acquiring it another thread could have switched the sock to TCP_LISTEN status - with a prior connect(AF_UNSPEC) - also clearing icsk_ack.rcv_mss. Address the issue preventing the disconnect if some other process is concurrently performing a blocking syscall on the same socket, alike commit 4faeee0cf8a5 ("tcp: deny tcp_disconnect() when threads are waiting"). Fixes: a6b118febbab ("mptcp: add receive buffer auto-tuning") Cc: stable@vger.kernel.org Reported-by: Christoph Paasch Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/404 Signed-off-by: Paolo Abeni Tested-by: Christoph Paasch Reviewed-by: Matthieu Baerts Signed-off-by: Matthieu Baerts Signed-off-by: Jakub Kicinski Signed-off-by: Matthieu Baerts --- Conflicting with 3e5014909b56 ("mptcp: cleanup MPJ subflow list handling") (and 7d803344fdc3 ("mptcp: fix deadlock in fastopen error path")). I took the new condition that I put first before doing any manipulation of the join list. Disconnect will be called later. Applied on top of d2efde0d1c2e ("Linux 5.15.119-rc1"). Signed-off-by: Matthieu Baerts --- net/mptcp/protocol.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c index b6a38af72e1b..f2977201f8fa 100644 --- a/net/mptcp/protocol.c +++ b/net/mptcp/protocol.c @@ -2807,6 +2807,12 @@ static int mptcp_disconnect(struct sock *sk, int fla= gs) struct mptcp_subflow_context *subflow; struct mptcp_sock *msk =3D mptcp_sk(sk); =20 + /* Deny disconnect if other threads are blocked in sk_wait_event() + * or inet_wait_for_connect(). + */ + if (sk->sk_wait_pending) + return -EBUSY; + mptcp_do_flush_join_list(msk); =20 mptcp_for_each_subflow(msk, subflow) { @@ -2845,6 +2851,7 @@ struct sock *mptcp_sk_clone(const struct sock *sk, inet_sk(nsk)->pinet6 =3D mptcp_inet6_sk(nsk); #endif =20 + nsk->sk_wait_pending =3D 0; __mptcp_init_sock(nsk); =20 msk =3D mptcp_sk(nsk); --=20 2.40.1