kernel.git/net/mptcp/protocol.h, branch linux-6.4.y

mptcp: fix disconnect vs accept race

2023-08-16T16:32:17Z

commit 511b90e39250135a7f900f1c3afbce25543018a2 upstream. Despite commit 0ad529d9fd2b ("mptcp: fix possible divide by zero in recvmsg()"), the mptcp protocol is still prone to a race between disconnect() (or shutdown) and accept. The root cause is that the mentioned commit checks the msk-level flag, but mptcp_stream_accept() does acquire the msk-level lock, as it can rely directly on the first subflow lock. As reported by Christoph than can lead to a race where an msk socket is accepted after that mptcp_subflow_queue_clean() releases the listener socket lock and just before it takes destructive actions leading to the following splat: BUG: kernel NULL pointer dereference, address: 0000000000000012 PGD 5a4ca067 P4D 5a4ca067 PUD 37d4c067 PMD 0 Oops: 0000 [#1] PREEMPT SMP CPU: 2 PID: 10955 Comm: syz-executor.5 Not tainted 6.5.0-rc1-gdc7b257ee5dd #37 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.11.0-2.el7 04/01/2014 RIP: 0010:mptcp_stream_accept+0x1ee/0x2f0 include/net/inet_sock.h:330 Code: 0a 09 00 48 8b 1b 4c 39 e3 74 07 e8 bc 7c 7f fe eb a1 e8 b5 7c 7f fe 4c 8b 6c 24 08 eb 05 e8 a9 7c 7f fe 49 8b 85 d8 09 00 00 <0f> b6 40 12 88 44 24 07 0f b6 6c 24 07 bf 07 00 00 00 89 ee e8 89 RSP: 0018:ffffc90000d07dc0 EFLAGS: 00010293 RAX: 0000000000000000 RBX: ffff888037e8d020 RCX: ffff88803b093300 RDX: 0000000000000000 RSI: ffffffff833822c5 RDI: ffffffff8333896a RBP: 0000607f82031520 R08: ffff88803b093300 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000003e83 R12: ffff888037e8d020 R13: ffff888037e8c680 R14: ffff888009af7900 R15: ffff888009af6880 FS: 00007fc26d708640(0000) GS:ffff88807dd00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000000000012 CR3: 0000000066bc5001 CR4: 0000000000370ee0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: do_accept+0x1ae/0x260 net/socket.c:1872 __sys_accept4+0x9b/0x110 net/socket.c:1913 __do_sys_accept4 net/socket.c:1954 [inline] __se_sys_accept4 net/socket.c:1951 [inline] __x64_sys_accept4+0x20/0x30 net/socket.c:1951 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+0x6e/0xd8 Address the issue by temporary removing the pending request socket from the accept queue, so that racing accept() can't touch them. After depleting the msk - the ssk still exists, as plain TCP sockets, re-insert them into the accept queue, so that later inet_csk_listen_stop() will complete the tcp socket disposal. Fixes: 2a6a870e44dd ("mptcp: stops worker on unaccepted sockets at listener close") Cc: stable@vger.kernel.org Reported-by: Christoph Paasch Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/423 Signed-off-by: Paolo Abeni Reviewed-by: Matthieu Baerts Signed-off-by: Matthieu Baerts Link: https://lore.kernel.org/r/20230803-upstream-net-20230803-misc-fixes-6-5-v1-4-6671b1ab11cc@tessares.net Signed-off-by: Jakub Kicinski Signed-off-by: Greg Kroah-Hartman

mptcp: drop legacy code around RX EOF

2023-06-22T05:44:54Z

Thanks to the previous patch -- "mptcp: consolidate fallback and non fallback state machine" -- we can finally drop the "temporary hack" used to detect rx eof. Signed-off-by: Paolo Abeni Reviewed-by: Mat Martineau Signed-off-by: Matthieu Baerts Signed-off-by: Jakub Kicinski

mptcp: only send RM_ADDR in nl_cmd_remove

2023-06-05T14:15:57Z

The specifications from [1] about the "REMOVE" command say: Announce that an address has been lost to the peer It was then only supposed to send a RM_ADDR and not trying to delete associated subflows. A new helper mptcp_pm_remove_addrs() is then introduced to do just that, compared to mptcp_pm_remove_addrs_and_subflows() also removing subflows. To delete a subflow, the userspace daemon can use the "SUB_DESTROY" command, see mptcp_nl_cmd_sf_destroy(). Fixes: d9a4594edabf ("mptcp: netlink: Add MPTCP_PM_CMD_REMOVE") Link: https://github.com/multipath-tcp/mptcp/blob/mptcp_v0.96/include/uapi/linux/mptcp.h [1] Cc: stable@vger.kernel.org Reviewed-by: Matthieu Baerts Signed-off-by: Geliang Tang Signed-off-by: Mat Martineau Signed-off-by: David S. Miller

mptcp: consolidate passive msk socket initialization

2023-06-01T17:04:04Z

When the msk socket is cloned at MPC handshake time, a few fields are initialized in a racy way outside mptcp_sk_clone() and the msk socket lock. The above is due historical reasons: before commit a88d0092b24b ("mptcp: simplify subflow_syn_recv_sock()") as the first subflow socket carrying all the needed date was not available yet at msk creation time We can now refactor the code moving the missing initialization bit under the socket lock, removing the init race and avoiding some code duplication. This will also simplify the next patch, as all msk->first write access are now under the msk socket lock. Fixes: 0397c6d85f9c ("mptcp: keep unaccepted MPC subflow into join list") Reviewed-by: Mat Martineau Signed-off-by: Paolo Abeni Signed-off-by: Mat Martineau Signed-off-by: Jakub Kicinski

mptcp: add annotations around msk->subflow accesses

2023-06-01T17:04:04Z

The MPTCP can access the first subflow socket in a few spots outside the socket lock scope. That is actually safe, as MPTCP will delete the socket itself only after the msk sock close(). Still the such accesses causes a few KCSAN splats, as reported by Christoph. Silence the harmless warning adding a few annotation around the relevant accesses. Fixes: 71ba088ce0aa ("mptcp: cleanup accept and poll") Reported-by: Christoph Paasch Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/402 Reviewed-by: Mat Martineau Signed-off-by: Paolo Abeni Signed-off-by: Mat Martineau Signed-off-by: Jakub Kicinski

mptcp: fix connect timeout handling

2023-06-01T17:04:04Z

Ondrej reported a functional issue WRT timeout handling on connect with a nice reproducer. The problem is that the current mptcp connect waits for both the MPTCP socket level timeout, and the first subflow socket timeout. The latter is not influenced/touched by the exposed setsockopt(). Overall the above makes the SO_SNDTIMEO a no-op on connect. Since mptcp_connect is invoked via inet_stream_connect and the latter properly handle the MPTCP level timeout, we can address the issue making the nested subflow level connect always unblocking. This also allow simplifying a bit the code, dropping an ugly hack to handle the fastopen and custom proto_ops connect. The issues predates the blamed commit below, but the current resolution requires the infrastructure introduced there. Fixes: 54f1944ed6d2 ("mptcp: factor out mptcp_connect()") Reported-by: Ondrej Mosnacek Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/399 Cc: stable@vger.kernel.org Reviewed-by: Mat Martineau Signed-off-by: Paolo Abeni Signed-off-by: Mat Martineau Signed-off-by: Jakub Kicinski

Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net

2023-04-20T23:29:51Z

Adjacent changes: net/mptcp/protocol.h 63740448a32e ("mptcp: fix accept vs worker race") 2a6a870e44dd ("mptcp: stops worker on unaccepted sockets at listener close") ddb1a072f858 ("mptcp: move first subflow allocation at mpc access time") Signed-off-by: Jakub Kicinski

mptcp: fix accept vs worker race

2023-04-19T08:08:37Z

The mptcp worker and mptcp_accept() can race, as reported by Christoph: refcount_t: addition on 0; use-after-free. WARNING: CPU: 1 PID: 14351 at lib/refcount.c:25 refcount_warn_saturate+0x105/0x1b0 lib/refcount.c:25 Modules linked in: CPU: 1 PID: 14351 Comm: syz-executor.2 Not tainted 6.3.0-rc1-gde5e8fd0123c #11 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.11.0-2.el7 04/01/2014 RIP: 0010:refcount_warn_saturate+0x105/0x1b0 lib/refcount.c:25 Code: 02 31 ff 89 de e8 1b f0 a7 ff 84 db 0f 85 6e ff ff ff e8 3e f5 a7 ff 48 c7 c7 d8 c7 34 83 c6 05 6d 2d 0f 02 01 e8 cb 3d 90 ff <0f> 0b e9 4f ff ff ff e8 1f f5 a7 ff 0f b6 1d 54 2d 0f 02 31 ff 89 RSP: 0018:ffffc90000a47bf8 EFLAGS: 00010282 RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000 RDX: ffff88802eae98c0 RSI: ffffffff81097d4f RDI: 0000000000000001 RBP: ffff88802e712180 R08: 0000000000000001 R09: 0000000000000000 R10: 0000000000000001 R11: ffff88802eaea148 R12: ffff88802e712100 R13: ffff88802e712a88 R14: ffff888005cb93a8 R15: ffff88802e712a88 FS: 0000000000000000(0000) GS:ffff88803ed00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f277fd89120 CR3: 0000000035486002 CR4: 0000000000370ee0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: __refcount_add include/linux/refcount.h:199 [inline] __refcount_inc include/linux/refcount.h:250 [inline] refcount_inc include/linux/refcount.h:267 [inline] sock_hold include/net/sock.h:775 [inline] __mptcp_close+0x4c6/0x4d0 net/mptcp/protocol.c:3051 mptcp_close+0x24/0xe0 net/mptcp/protocol.c:3072 inet_release+0x56/0xa0 net/ipv4/af_inet.c:429 __sock_release+0x51/0xf0 net/socket.c:653 sock_close+0x18/0x20 net/socket.c:1395 __fput+0x113/0x430 fs/file_table.c:321 task_work_run+0x96/0x100 kernel/task_work.c:179 exit_task_work include/linux/task_work.h:38 [inline] do_exit+0x4fc/0x10c0 kernel/exit.c:869 do_group_exit+0x51/0xf0 kernel/exit.c:1019 get_signal+0x12b0/0x1390 kernel/signal.c:2859 arch_do_signal_or_restart+0x25/0x260 arch/x86/kernel/signal.c:306 exit_to_user_mode_loop kernel/entry/common.c:168 [inline] exit_to_user_mode_prepare+0x131/0x1a0 kernel/entry/common.c:203 __syscall_exit_to_user_mode_work kernel/entry/common.c:285 [inline] syscall_exit_to_user_mode+0x19/0x40 kernel/entry/common.c:296 do_syscall_64+0x46/0x90 arch/x86/entry/common.c:86 entry_SYSCALL_64_after_hwframe+0x72/0xdc RIP: 0033:0x7fec4b4926a9 Code: Unable to access opcode bytes at 0x7fec4b49267f. RSP: 002b:00007fec49f9dd78 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca RAX: fffffffffffffe00 RBX: 00000000006bc058 RCX: 00007fec4b4926a9 RDX: 0000000000000000 RSI: 0000000000000080 RDI: 00000000006bc058 RBP: 00000000006bc050 R08: 00000000007df998 R09: 00000000007df998 R10: 0000000000000000 R11: 0000000000000246 R12: 00000000006bc05c R13: fffffffffffffea8 R14: 000000000000000b R15: 000000000001fe40 The root cause is that the worker can force fallback to TCP the first mptcp subflow, actually deleting the unaccepted msk socket. We can explicitly prevent the race delaying the unaccepted msk deletion at listener shutdown time. In case the closed subflow is later accepted, just drop the mptcp context and let the user-space deal with the paired mptcp socket. Fixes: b6985b9b8295 ("mptcp: use the workqueue to destroy unaccepted sockets") Cc: stable@vger.kernel.org Reported-by: Christoph Paasch Link: https://github.com/multipath-tcp/mptcp_net-next/issues/375 Signed-off-by: Paolo Abeni Reviewed-by: Matthieu Baerts Tested-by: Christoph Paasch Signed-off-by: Matthieu Baerts Signed-off-by: David S. Miller

mptcp: stops worker on unaccepted sockets at listener close

2023-04-19T08:08:36Z

This is a partial revert of the blamed commit, with a relevant change: mptcp_subflow_queue_clean() now just change the msk socket status and stop the worker, so that the UaF issue addressed by the blamed commit is not re-introduced. The above prevents the mptcp worker from running concurrently with inet_csk_listen_stop(), as such race would trigger a warning, as reported by Christoph: RSP: 002b:00007f784fe09cd8 EFLAGS: 00000246 ORIG_RAX: 000000000000002e WARNING: CPU: 0 PID: 25807 at net/ipv4/inet_connection_sock.c:1387 inet_csk_listen_stop+0x664/0x870 net/ipv4/inet_connection_sock.c:1387 RAX: ffffffffffffffda RBX: 00000000006bc050 RCX: 00007f7850afd6a9 RDX: 0000000000000000 RSI: 0000000020000340 RDI: 0000000000000004 Modules linked in: RBP: 0000000000000002 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 00000000006bc05c R13: fffffffffffffea8 R14: 00000000006bc050 R15: 000000000001fe40 CPU: 0 PID: 25807 Comm: syz-executor.7 Not tainted 6.2.0-g778e54711659 #7 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.11.0-2.el7 04/01/2014 RIP: 0010:inet_csk_listen_stop+0x664/0x870 net/ipv4/inet_connection_sock.c:1387 RAX: 0000000000000000 RBX: ffff888100dfbd40 RCX: 0000000000000000 RDX: ffff8881363aab80 RSI: ffffffff81c494f4 RDI: 0000000000000005 RBP: ffff888126dad080 R08: 0000000000000005 R09: 0000000000000000 R10: 0000000000000001 R11: 0000000000000000 R12: ffff888100dfe040 R13: 0000000000000001 R14: 0000000000000000 R15: ffff888100dfbdd8 FS: 00007f7850a2c800(0000) GS:ffff88813bc00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000001b32d26000 CR3: 000000012fdd8006 CR4: 0000000000770ef0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 PKRU: 55555554 Call Trace: __tcp_close+0x5b2/0x620 net/ipv4/tcp.c:2875 __mptcp_close_ssk+0x145/0x3d0 net/mptcp/protocol.c:2427 mptcp_destroy_common+0x8a/0x1c0 net/mptcp/protocol.c:3277 mptcp_destroy+0x41/0x60 net/mptcp/protocol.c:3304 __mptcp_destroy_sock+0x56/0x140 net/mptcp/protocol.c:2965 __mptcp_close+0x38f/0x4a0 net/mptcp/protocol.c:3057 mptcp_close+0x24/0xe0 net/mptcp/protocol.c:3072 inet_release+0x53/0xa0 net/ipv4/af_inet.c:429 __sock_release+0x4e/0xf0 net/socket.c:651 sock_close+0x15/0x20 net/socket.c:1393 __fput+0xff/0x420 fs/file_table.c:321 task_work_run+0x8b/0xe0 kernel/task_work.c:179 resume_user_mode_work include/linux/resume_user_mode.h:49 [inline] exit_to_user_mode_loop kernel/entry/common.c:171 [inline] exit_to_user_mode_prepare+0x113/0x120 kernel/entry/common.c:203 __syscall_exit_to_user_mode_work kernel/entry/common.c:285 [inline] syscall_exit_to_user_mode+0x1d/0x40 kernel/entry/common.c:296 do_syscall_64+0x46/0x90 arch/x86/entry/common.c:86 entry_SYSCALL_64_after_hwframe+0x72/0xdc RIP: 0033:0x7f7850af70dc RAX: 0000000000000000 RBX: 0000000000000004 RCX: 00007f7850af70dc RDX: 00007f7850a2c800 RSI: 0000000000000002 RDI: 0000000000000003 RBP: 00000000006bd980 R08: 0000000000000000 R09: 00000000000018a0 R10: 00000000316338a4 R11: 0000000000000293 R12: 0000000000211e31 R13: 00000000006bc05c R14: 00007f785062c000 R15: 0000000000211af0 Fixes: 0a3f4f1f9c27 ("mptcp: fix UaF in listener shutdown") Cc: stable@vger.kernel.org Reported-by: Christoph Paasch Link: https://github.com/multipath-tcp/mptcp_net-next/issues/371 Signed-off-by: Paolo Abeni Reviewed-by: Matthieu Baerts Signed-off-by: Matthieu Baerts Signed-off-by: David S. Miller

mptcp: make userspace_pm_append_new_local_addr static

2023-04-17T07:25:33Z

mptcp_userspace_pm_append_new_local_addr() has always exclusively been used in pm_userspace.c since its introduction in commit 4638de5aefe5 ("mptcp: handle local addrs announced by userspace PMs"). So make it static. Signed-off-by: Geliang Tang Reviewed-by: Matthieu Baerts Signed-off-by: Matthieu Baerts Signed-off-by: David S. Miller