* [PATCH v2] net: ax25: Fix deadlock caused by skb_recv_datagram in ax25_recvmsg
@ 2022-06-07 14:23 Duoming Zhou
2022-06-07 17:06 ` Eric Dumazet
0 siblings, 1 reply; 3+ messages in thread
From: Duoming Zhou @ 2022-06-07 14:23 UTC (permalink / raw)
To: linux-kernel
Cc: jreuter, ralf, davem, edumazet, kuba, pabeni, netdev, linux-hams,
thomas, Duoming Zhou
The skb_recv_datagram() in ax25_recvmsg() will hold lock_sock
and block until it receives a packet from the remote. If the client
doesn`t connect to server and calls read() directly, it will not
receive any packets forever. As a result, the deadlock will happen.
The fail log caused by deadlock is shown below:
[ 369.606973] INFO: task ax25_deadlock:157 blocked for more than 245 seconds.
[ 369.608919] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[ 369.613058] Call Trace:
[ 369.613315] <TASK>
[ 369.614072] __schedule+0x2f9/0xb20
[ 369.615029] schedule+0x49/0xb0
[ 369.615734] __lock_sock+0x92/0x100
[ 369.616763] ? destroy_sched_domains_rcu+0x20/0x20
[ 369.617941] lock_sock_nested+0x6e/0x70
[ 369.618809] ax25_bind+0xaa/0x210
[ 369.619736] __sys_bind+0xca/0xf0
[ 369.620039] ? do_futex+0xae/0x1b0
[ 369.620387] ? __x64_sys_futex+0x7c/0x1c0
[ 369.620601] ? fpregs_assert_state_consistent+0x19/0x40
[ 369.620613] __x64_sys_bind+0x11/0x20
[ 369.621791] do_syscall_64+0x3b/0x90
[ 369.622423] entry_SYSCALL_64_after_hwframe+0x46/0xb0
[ 369.623319] RIP: 0033:0x7f43c8aa8af7
[ 369.624301] RSP: 002b:00007f43c8197ef8 EFLAGS: 00000246 ORIG_RAX: 0000000000000031
[ 369.625756] RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f43c8aa8af7
[ 369.626724] RDX: 0000000000000010 RSI: 000055768e2021d0 RDI: 0000000000000005
[ 369.628569] RBP: 00007f43c8197f00 R08: 0000000000000011 R09: 00007f43c8198700
[ 369.630208] R10: 0000000000000000 R11: 0000000000000246 R12: 00007fff845e6afe
[ 369.632240] R13: 00007fff845e6aff R14: 00007f43c8197fc0 R15: 00007f43c8198700
This patch moves the skb_recv_datagram() before lock_sock() in order
that other functions that need lock_sock could be executed.
Suggested-by: Thomas Osterried <thomas@osterried.de>
Signed-off-by: Duoming Zhou <duoming@zju.edu.cn>
Reported-by: Thomas Habets <thomas@@habets.se>
---
Changes in v2:
- Make commit messages clearer.
net/ax25/af_ax25.c | 11 ++++++-----
1 file changed, 6 insertions(+), 5 deletions(-)
diff --git a/net/ax25/af_ax25.c b/net/ax25/af_ax25.c
index 95393bb2760..02cd6087512 100644
--- a/net/ax25/af_ax25.c
+++ b/net/ax25/af_ax25.c
@@ -1665,6 +1665,11 @@ static int ax25_recvmsg(struct socket *sock, struct msghdr *msg, size_t size,
int copied;
int err = 0;
+ /* Now we can treat all alike */
+ skb = skb_recv_datagram(sk, flags, &err);
+ if (!skb)
+ goto done;
+
lock_sock(sk);
/*
* This works for seqpacket too. The receiver has ordered the
@@ -1675,11 +1680,6 @@ static int ax25_recvmsg(struct socket *sock, struct msghdr *msg, size_t size,
goto out;
}
- /* Now we can treat all alike */
- skb = skb_recv_datagram(sk, flags, &err);
- if (skb == NULL)
- goto out;
-
if (!sk_to_ax25(sk)->pidincl)
skb_pull(skb, 1); /* Remove PID */
@@ -1725,6 +1725,7 @@ static int ax25_recvmsg(struct socket *sock, struct msghdr *msg, size_t size,
out:
release_sock(sk);
+done:
return err;
}
--
2.17.1
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH v2] net: ax25: Fix deadlock caused by skb_recv_datagram in ax25_recvmsg
2022-06-07 14:23 [PATCH v2] net: ax25: Fix deadlock caused by skb_recv_datagram in ax25_recvmsg Duoming Zhou
@ 2022-06-07 17:06 ` Eric Dumazet
2022-06-08 1:02 ` duoming
0 siblings, 1 reply; 3+ messages in thread
From: Eric Dumazet @ 2022-06-07 17:06 UTC (permalink / raw)
To: Duoming Zhou
Cc: LKML, jreuter, Ralf Baechle, David Miller, Jakub Kicinski,
Paolo Abeni, netdev, linux-hams, thomas
On Tue, Jun 7, 2022 at 7:24 AM Duoming Zhou <duoming@zju.edu.cn> wrote:
>
> The skb_recv_datagram() in ax25_recvmsg() will hold lock_sock
> and block until it receives a packet from the remote. If the client
> doesn`t connect to server and calls read() directly, it will not
> receive any packets forever. As a result, the deadlock will happen.
>
> The fail log caused by deadlock is shown below:
>
> [ 369.606973] INFO: task ax25_deadlock:157 blocked for more than 245 seconds.
> [ 369.608919] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> [ 369.613058] Call Trace:
> [ 369.613315] <TASK>
> [ 369.614072] __schedule+0x2f9/0xb20
> [ 369.615029] schedule+0x49/0xb0
> [ 369.615734] __lock_sock+0x92/0x100
> [ 369.616763] ? destroy_sched_domains_rcu+0x20/0x20
> [ 369.617941] lock_sock_nested+0x6e/0x70
> [ 369.618809] ax25_bind+0xaa/0x210
> [ 369.619736] __sys_bind+0xca/0xf0
> [ 369.620039] ? do_futex+0xae/0x1b0
> [ 369.620387] ? __x64_sys_futex+0x7c/0x1c0
> [ 369.620601] ? fpregs_assert_state_consistent+0x19/0x40
> [ 369.620613] __x64_sys_bind+0x11/0x20
> [ 369.621791] do_syscall_64+0x3b/0x90
> [ 369.622423] entry_SYSCALL_64_after_hwframe+0x46/0xb0
> [ 369.623319] RIP: 0033:0x7f43c8aa8af7
> [ 369.624301] RSP: 002b:00007f43c8197ef8 EFLAGS: 00000246 ORIG_RAX: 0000000000000031
> [ 369.625756] RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f43c8aa8af7
> [ 369.626724] RDX: 0000000000000010 RSI: 000055768e2021d0 RDI: 0000000000000005
> [ 369.628569] RBP: 00007f43c8197f00 R08: 0000000000000011 R09: 00007f43c8198700
> [ 369.630208] R10: 0000000000000000 R11: 0000000000000246 R12: 00007fff845e6afe
> [ 369.632240] R13: 00007fff845e6aff R14: 00007f43c8197fc0 R15: 00007f43c8198700
>
> This patch moves the skb_recv_datagram() before lock_sock() in order
> that other functions that need lock_sock could be executed.
>
> Suggested-by: Thomas Osterried <thomas@osterried.de>
> Signed-off-by: Duoming Zhou <duoming@zju.edu.cn>
> Reported-by: Thomas Habets <thomas@@habets.se>
> ---
> Changes in v2:
> - Make commit messages clearer.
>
> net/ax25/af_ax25.c | 11 ++++++-----
> 1 file changed, 6 insertions(+), 5 deletions(-)
>
> diff --git a/net/ax25/af_ax25.c b/net/ax25/af_ax25.c
> index 95393bb2760..02cd6087512 100644
> --- a/net/ax25/af_ax25.c
> +++ b/net/ax25/af_ax25.c
> @@ -1665,6 +1665,11 @@ static int ax25_recvmsg(struct socket *sock, struct msghdr *msg, size_t size,
> int copied;
> int err = 0;
>
> + /* Now we can treat all alike */
> + skb = skb_recv_datagram(sk, flags, &err);
> + if (!skb)
> + goto done;
> +
So at this point we have skb=something. This means that the following
branch will leak it.
if (sk->sk_type == SOCK_SEQPACKET && sk->sk_state != TCP_ESTABLISHED) {
err = -ENOTCONN;
goto out; // skb will be leaked
}
> /*
> * This works for seqpacket too. The receiver has ordered the
> @@ -1675,11 +1680,6 @@ static int ax25_recvmsg(struct socket *sock, struct msghdr *msg, size_t size,
> goto out;
> }
>
> - /* Now we can treat all alike */
> - skb = skb_recv_datagram(sk, flags, &err);
> - if (skb == NULL)
> - goto out;
> -
> if (!sk_to_ax25(sk)->pidincl)
> skb_pull(skb, 1); /* Remove PID */
>
> @@ -1725,6 +1725,7 @@ static int ax25_recvmsg(struct socket *sock, struct msghdr *msg, size_t size,
> out:
> release_sock(sk);
>
> +done:
> return err;
> }
>
> --
> 2.17.1
>
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH v2] net: ax25: Fix deadlock caused by skb_recv_datagram in ax25_recvmsg
2022-06-07 17:06 ` Eric Dumazet
@ 2022-06-08 1:02 ` duoming
0 siblings, 0 replies; 3+ messages in thread
From: duoming @ 2022-06-08 1:02 UTC (permalink / raw)
To: Eric Dumazet
Cc: LKML, jreuter, Ralf Baechle, David Miller, Jakub Kicinski,
Paolo Abeni, netdev, linux-hams, thomas
Hello,
On Tue, 7 Jun 2022 10:06:27 -0700 Eric Dumazet wrote:
> On Tue, Jun 7, 2022 at 7:24 AM Duoming Zhou <duoming@zju.edu.cn> wrote:
> >
> > The skb_recv_datagram() in ax25_recvmsg() will hold lock_sock
> > and block until it receives a packet from the remote. If the client
> > doesn`t connect to server and calls read() directly, it will not
> > receive any packets forever. As a result, the deadlock will happen.
> >
> > The fail log caused by deadlock is shown below:
> >
> > [ 369.606973] INFO: task ax25_deadlock:157 blocked for more than 245 seconds.
> > [ 369.608919] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> > [ 369.613058] Call Trace:
> > [ 369.613315] <TASK>
> > [ 369.614072] __schedule+0x2f9/0xb20
> > [ 369.615029] schedule+0x49/0xb0
> > [ 369.615734] __lock_sock+0x92/0x100
> > [ 369.616763] ? destroy_sched_domains_rcu+0x20/0x20
> > [ 369.617941] lock_sock_nested+0x6e/0x70
> > [ 369.618809] ax25_bind+0xaa/0x210
> > [ 369.619736] __sys_bind+0xca/0xf0
> > [ 369.620039] ? do_futex+0xae/0x1b0
> > [ 369.620387] ? __x64_sys_futex+0x7c/0x1c0
> > [ 369.620601] ? fpregs_assert_state_consistent+0x19/0x40
> > [ 369.620613] __x64_sys_bind+0x11/0x20
> > [ 369.621791] do_syscall_64+0x3b/0x90
> > [ 369.622423] entry_SYSCALL_64_after_hwframe+0x46/0xb0
> > [ 369.623319] RIP: 0033:0x7f43c8aa8af7
> > [ 369.624301] RSP: 002b:00007f43c8197ef8 EFLAGS: 00000246 ORIG_RAX: 0000000000000031
> > [ 369.625756] RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f43c8aa8af7
> > [ 369.626724] RDX: 0000000000000010 RSI: 000055768e2021d0 RDI: 0000000000000005
> > [ 369.628569] RBP: 00007f43c8197f00 R08: 0000000000000011 R09: 00007f43c8198700
> > [ 369.630208] R10: 0000000000000000 R11: 0000000000000246 R12: 00007fff845e6afe
> > [ 369.632240] R13: 00007fff845e6aff R14: 00007f43c8197fc0 R15: 00007f43c8198700
> >
> > This patch moves the skb_recv_datagram() before lock_sock() in order
> > that other functions that need lock_sock could be executed.
> >
> > Suggested-by: Thomas Osterried <thomas@osterried.de>
> > Signed-off-by: Duoming Zhou <duoming@zju.edu.cn>
> > Reported-by: Thomas Habets <thomas@@habets.se>
> > ---
> > Changes in v2:
> > - Make commit messages clearer.
> >
> > net/ax25/af_ax25.c | 11 ++++++-----
> > 1 file changed, 6 insertions(+), 5 deletions(-)
> >
> > diff --git a/net/ax25/af_ax25.c b/net/ax25/af_ax25.c
> > index 95393bb2760..02cd6087512 100644
> > --- a/net/ax25/af_ax25.c
> > +++ b/net/ax25/af_ax25.c
> > @@ -1665,6 +1665,11 @@ static int ax25_recvmsg(struct socket *sock, struct msghdr *msg, size_t size,
> > int copied;
> > int err = 0;
> >
> > + /* Now we can treat all alike */
> > + skb = skb_recv_datagram(sk, flags, &err);
> > + if (!skb)
> > + goto done;
> > +
>
> So at this point we have skb=something. This means that the following
> branch will leak it.
>
> if (sk->sk_type == SOCK_SEQPACKET && sk->sk_state != TCP_ESTABLISHED) {
> err = -ENOTCONN;
> goto out; // skb will be leaked
> }
>
Thank your for pointing out the problem!
I will add skb_free_datagram() before goto out in order to mitigate the memory leak.
if (sk->sk_type == SOCK_SEQPACKET && sk->sk_state != TCP_ESTABLISHED) {
err = -ENOTCONN;
+ skb_free_datagram(sk, skb);
goto out;
}
Best regards,
Duoming Zhou
^ permalink raw reply [flat|nested] 3+ messages in thread
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2022-06-07 14:23 [PATCH v2] net: ax25: Fix deadlock caused by skb_recv_datagram in ax25_recvmsg Duoming Zhou
2022-06-07 17:06 ` Eric Dumazet
2022-06-08 1:02 ` duoming
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