From: Eric Dumazet edumazet@google.com
[ Upstream commit 4faeee0cf8a5d88d63cdbc3bab124fb0e6aed08c ]
Historically connect(AF_UNSPEC) has been abused by syzkaller and other fuzzers to trigger various bugs.
A recent one triggers a divide-by-zero [1], and Paolo Abeni was able to diagnose the issue.
tcp_recvmsg_locked() has tests about sk_state being not TCP_LISTEN and TCP REPAIR mode being not used.
Then later if socket lock is released in sk_wait_data(), another thread can call connect(AF_UNSPEC), then make this socket a TCP listener.
When recvmsg() is resumed, it can eventually call tcp_cleanup_rbuf() and attempt a divide by 0 in tcp_rcv_space_adjust() [1]
This patch adds a new socket field, counting number of threads blocked in sk_wait_event() and inet_wait_for_connect().
If this counter is not zero, tcp_disconnect() returns an error.
This patch adds code in blocking socket system calls, thus should not hurt performance of non blocking ones.
Note that we probably could revert commit 499350a5a6e7 ("tcp: initialize rcv_mss to TCP_MIN_MSS instead of 0") to restore original tcpi_rcv_mss meaning (was 0 if no payload was ever received on a socket)
[1] divide error: 0000 [#1] PREEMPT SMP KASAN CPU: 0 PID: 13832 Comm: syz-executor.5 Not tainted 6.3.0-rc4-syzkaller-00224-g00c7b5f4ddc5 #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/02/2023 RIP: 0010:tcp_rcv_space_adjust+0x36e/0x9d0 net/ipv4/tcp_input.c:740 Code: 00 00 00 00 fc ff df 4c 89 64 24 48 8b 44 24 04 44 89 f9 41 81 c7 80 03 00 00 c1 e1 04 44 29 f0 48 63 c9 48 01 e9 48 0f af c1 <49> f7 f6 48 8d 04 41 48 89 44 24 40 48 8b 44 24 30 48 c1 e8 03 48 RSP: 0018:ffffc900033af660 EFLAGS: 00010206 RAX: 4a66b76cbade2c48 RBX: ffff888076640cc0 RCX: 00000000c334e4ac RDX: 0000000000000000 RSI: dffffc0000000000 RDI: 0000000000000001 RBP: 00000000c324e86c R08: 0000000000000001 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000000 R12: ffff8880766417f8 R13: ffff888028fbb980 R14: 0000000000000000 R15: 0000000000010344 FS: 00007f5bffbfe700(0000) GS:ffff8880b9800000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000001b32f25000 CR3: 000000007ced0000 CR4: 00000000003506f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: <TASK> tcp_recvmsg_locked+0x100e/0x22e0 net/ipv4/tcp.c:2616 tcp_recvmsg+0x117/0x620 net/ipv4/tcp.c:2681 inet6_recvmsg+0x114/0x640 net/ipv6/af_inet6.c:670 sock_recvmsg_nosec net/socket.c:1017 [inline] sock_recvmsg+0xe2/0x160 net/socket.c:1038 ____sys_recvmsg+0x210/0x5a0 net/socket.c:2720 ___sys_recvmsg+0xf2/0x180 net/socket.c:2762 do_recvmmsg+0x25e/0x6e0 net/socket.c:2856 __sys_recvmmsg net/socket.c:2935 [inline] __do_sys_recvmmsg net/socket.c:2958 [inline] __se_sys_recvmmsg net/socket.c:2951 [inline] __x64_sys_recvmmsg+0x20f/0x260 net/socket.c:2951 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x39/0xb0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x63/0xcd RIP: 0033:0x7f5c0108c0f9 Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 f1 19 00 00 90 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 ff 73 01 c3 48 c7 c1 b8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007f5bffbfe168 EFLAGS: 00000246 ORIG_RAX: 000000000000012b RAX: ffffffffffffffda RBX: 00007f5c011ac050 RCX: 00007f5c0108c0f9 RDX: 0000000000000001 RSI: 0000000020000bc0 RDI: 0000000000000003 RBP: 00007f5c010e7b39 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000122 R11: 0000000000000246 R12: 0000000000000000 R13: 00007f5c012cfb1f R14: 00007f5bffbfe300 R15: 0000000000022000 </TASK>
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Reported-by: syzbot syzkaller@googlegroups.com Reported-by: Paolo Abeni pabeni@redhat.com Diagnosed-by: Paolo Abeni pabeni@redhat.com Signed-off-by: Eric Dumazet edumazet@google.com Tested-by: Paolo Abeni pabeni@redhat.com Link: https://lore.kernel.org/r/20230526163458.2880232-1-edumazet@google.com Signed-off-by: Jakub Kicinski kuba@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- include/net/sock.h | 4 ++++ net/ipv4/af_inet.c | 2 ++ net/ipv4/inet_connection_sock.c | 1 + net/ipv4/tcp.c | 6 ++++++ 4 files changed, 13 insertions(+)
diff --git a/include/net/sock.h b/include/net/sock.h index cfbd241935a30..c140c6f86e4b1 100644 --- a/include/net/sock.h +++ b/include/net/sock.h @@ -312,6 +312,7 @@ struct sock_common { * @sk_cgrp_data: cgroup data for this cgroup * @sk_memcg: this socket's memory cgroup association * @sk_write_pending: a write to stream socket waits to start + * @sk_wait_pending: number of threads blocked on this socket * @sk_state_change: callback to indicate change in the state of the sock * @sk_data_ready: callback to indicate there is data to be processed * @sk_write_space: callback to indicate there is bf sending space available @@ -392,6 +393,7 @@ struct sock { unsigned int sk_napi_id; #endif int sk_rcvbuf; + int sk_wait_pending;
struct sk_filter __rcu *sk_filter; union { @@ -1010,6 +1012,7 @@ static inline void sock_rps_reset_rxhash(struct sock *sk)
#define sk_wait_event(__sk, __timeo, __condition, __wait) \ ({ int __rc; \ + __sk->sk_wait_pending++; \ release_sock(__sk); \ __rc = __condition; \ if (!__rc) { \ @@ -1019,6 +1022,7 @@ static inline void sock_rps_reset_rxhash(struct sock *sk) } \ sched_annotate_sleep(); \ lock_sock(__sk); \ + __sk->sk_wait_pending--; \ __rc = __condition; \ __rc; \ }) diff --git a/net/ipv4/af_inet.c b/net/ipv4/af_inet.c index fb142ea730060..7c902a1efbbf6 100644 --- a/net/ipv4/af_inet.c +++ b/net/ipv4/af_inet.c @@ -578,6 +578,7 @@ static long inet_wait_for_connect(struct sock *sk, long timeo, int writebias)
add_wait_queue(sk_sleep(sk), &wait); sk->sk_write_pending += writebias; + sk->sk_wait_pending++;
/* Basic assumption: if someone sets sk->sk_err, he _must_ * change state of the socket from TCP_SYN_*. @@ -593,6 +594,7 @@ static long inet_wait_for_connect(struct sock *sk, long timeo, int writebias) } remove_wait_queue(sk_sleep(sk), &wait); sk->sk_write_pending -= writebias; + sk->sk_wait_pending--; return timeo; }
diff --git a/net/ipv4/inet_connection_sock.c b/net/ipv4/inet_connection_sock.c index 0f9085220ecf9..7392a744c677e 100644 --- a/net/ipv4/inet_connection_sock.c +++ b/net/ipv4/inet_connection_sock.c @@ -826,6 +826,7 @@ struct sock *inet_csk_clone_lock(const struct sock *sk, if (newsk) { struct inet_connection_sock *newicsk = inet_csk(newsk);
+ newsk->sk_wait_pending = 0; inet_sk_set_state(newsk, TCP_SYN_RECV); newicsk->icsk_bind_hash = NULL;
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c index b51e0a1e15b67..22218ad71409f 100644 --- a/net/ipv4/tcp.c +++ b/net/ipv4/tcp.c @@ -2568,6 +2568,12 @@ int tcp_disconnect(struct sock *sk, int flags) int old_state = sk->sk_state; u32 seq;
+ /* Deny disconnect if other threads are blocked in sk_wait_event() + * or inet_wait_for_connect(). + */ + if (sk->sk_wait_pending) + return -EBUSY; + if (old_state != TCP_CLOSE) tcp_set_state(sk, TCP_CLOSE);