tcp: deny tcp_disconnect() when threads are waiting

[ 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>

diff --git a/include/net/sock.h b/include/net/sock.h
index beb1b74..f11b98b 100644 (file)
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -333,6 +333,7 @@ struct sk_filter;
   *    @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_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
   *    @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


@@ -425,6 +426,7 @@ struct sock {
        unsigned int            sk_napi_id;
 #endif
        int                     sk_rcvbuf;
        unsigned int            sk_napi_id;
 #endif
        int                     sk_rcvbuf;

+       int                     sk_wait_pending;

 
        struct sk_filter __rcu  *sk_filter;
        union {
 
        struct sk_filter __rcu  *sk_filter;
        union {


@@ -1170,6 +1172,7 @@ static inline void sock_rps_reset_rxhash(struct sock *sk)
 
 #define sk_wait_event(__sk, __timeo, __condition, __wait)              \
        ({      int __rc;                                               \
 
 #define sk_wait_event(__sk, __timeo, __condition, __wait)              \
        ({      int __rc;                                               \

+               __sk->sk_wait_pending++;                                \

                release_sock(__sk);                                     \
                __rc = __condition;                                     \
                if (!__rc) {                                            \
                release_sock(__sk);                                     \
                __rc = __condition;                                     \
                if (!__rc) {                                            \


@@ -1179,6 +1182,7 @@ static inline void sock_rps_reset_rxhash(struct sock *sk)
                }                                                       \
                sched_annotate_sleep();                                 \
                lock_sock(__sk);                                        \
                }                                                       \
                sched_annotate_sleep();                                 \
                lock_sock(__sk);                                        \

+               __sk->sk_wait_pending--;                                \

                __rc = __condition;                                     \
                __rc;                                                   \
        })
                __rc = __condition;                                     \
                __rc;                                                   \
        })

diff --git a/net/ipv4/af_inet.c b/net/ipv4/af_inet.c
index 5fd0ff5..ebb737a 100644 (file)
--- a/net/ipv4/af_inet.c
+++ b/net/ipv4/af_inet.c
@@ -589,6 +589,7 @@ 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;
 
        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_*.
 
        /* Basic assumption: if someone sets sk->sk_err, he _must_
         * change state of the socket from TCP_SYN_*.


@@ -604,6 +605,7 @@ 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;
        }
        remove_wait_queue(sk_sleep(sk), &wait);
        sk->sk_write_pending -= writebias;

+       sk->sk_wait_pending--;

        return timeo;
 }
 
        return timeo;
 }
 

diff --git a/net/ipv4/inet_connection_sock.c b/net/ipv4/inet_connection_sock.c
index 916075e..8e35ea6 100644 (file)
--- a/net/ipv4/inet_connection_sock.c
+++ b/net/ipv4/inet_connection_sock.c
@@ -1143,6 +1143,7 @@ struct sock *inet_csk_clone_lock(const struct sock *sk,
        if (newsk) {
                struct inet_connection_sock *newicsk = inet_csk(newsk);
 
        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;
                newicsk->icsk_bind2_hash = NULL;
                inet_sk_set_state(newsk, TCP_SYN_RECV);
                newicsk->icsk_bind_hash = NULL;
                newicsk->icsk_bind2_hash = NULL;

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 021a8bf..c77b57d 100644 (file)
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -3079,6 +3079,12 @@ int tcp_disconnect(struct sock *sk, int flags)
        int old_state = sk->sk_state;
        u32 seq;
 
        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);
 
        if (old_state != TCP_CLOSE)
                tcp_set_state(sk, TCP_CLOSE);