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Date: Tue, 1 Oct 2019 09:28:31 +0200
From: Stefano Garzarella <sgarzare@...hat.com>
To: Dexuan Cui <decui@...rosoft.com>
Cc: "davem@...emloft.net" <davem@...emloft.net>,
KY Srinivasan <kys@...rosoft.com>,
Haiyang Zhang <haiyangz@...rosoft.com>,
Stephen Hemminger <sthemmin@...rosoft.com>,
"sashal@...nel.org" <sashal@...nel.org>,
"stefanha@...hat.com" <stefanha@...hat.com>,
"gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
"arnd@...db.de" <arnd@...db.de>,
"deepa.kernel@...il.com" <deepa.kernel@...il.com>,
"ytht.net@...il.com" <ytht.net@...il.com>,
"tglx@...utronix.de" <tglx@...utronix.de>,
"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
"kvm@...r.kernel.org" <kvm@...r.kernel.org>,
"virtualization@...ts.linux-foundation.org"
<virtualization@...ts.linux-foundation.org>,
Michael Kelley <mikelley@...rosoft.com>,
"jhansen@...are.com" <jhansen@...are.com>
Subject: Re: [PATCH net v3] vsock: Fix a lockdep warning in __vsock_release()
On Mon, Sep 30, 2019 at 06:43:50PM +0000, Dexuan Cui wrote:
> Lockdep is unhappy if two locks from the same class are held.
>
> Fix the below warning for hyperv and virtio sockets (vmci socket code
> doesn't have the issue) by using lock_sock_nested() when __vsock_release()
> is called recursively:
>
> ============================================
> WARNING: possible recursive locking detected
> 5.3.0+ #1 Not tainted
> --------------------------------------------
> server/1795 is trying to acquire lock:
> ffff8880c5158990 (sk_lock-AF_VSOCK){+.+.}, at: hvs_release+0x10/0x120 [hv_sock]
>
> but task is already holding lock:
> ffff8880c5158150 (sk_lock-AF_VSOCK){+.+.}, at: __vsock_release+0x2e/0xf0 [vsock]
>
> other info that might help us debug this:
> Possible unsafe locking scenario:
>
> CPU0
> ----
> lock(sk_lock-AF_VSOCK);
> lock(sk_lock-AF_VSOCK);
>
> *** DEADLOCK ***
>
> May be due to missing lock nesting notation
>
> 2 locks held by server/1795:
> #0: ffff8880c5d05ff8 (&sb->s_type->i_mutex_key#10){+.+.}, at: __sock_release+0x2d/0xa0
> #1: ffff8880c5158150 (sk_lock-AF_VSOCK){+.+.}, at: __vsock_release+0x2e/0xf0 [vsock]
>
> stack backtrace:
> CPU: 5 PID: 1795 Comm: server Not tainted 5.3.0+ #1
> Call Trace:
> dump_stack+0x67/0x90
> __lock_acquire.cold.67+0xd2/0x20b
> lock_acquire+0xb5/0x1c0
> lock_sock_nested+0x6d/0x90
> hvs_release+0x10/0x120 [hv_sock]
> __vsock_release+0x24/0xf0 [vsock]
> __vsock_release+0xa0/0xf0 [vsock]
> vsock_release+0x12/0x30 [vsock]
> __sock_release+0x37/0xa0
> sock_close+0x14/0x20
> __fput+0xc1/0x250
> task_work_run+0x98/0xc0
> do_exit+0x344/0xc60
> do_group_exit+0x47/0xb0
> get_signal+0x15c/0xc50
> do_signal+0x30/0x720
> exit_to_usermode_loop+0x50/0xa0
> do_syscall_64+0x24e/0x270
> entry_SYSCALL_64_after_hwframe+0x49/0xbe
> RIP: 0033:0x7f4184e85f31
>
> Tested-by: Stefano Garzarella <sgarzare@...hat.com>
> Signed-off-by: Dexuan Cui <decui@...rosoft.com>
> ---
The patch LGTM and and functionally it's the same as the v2 that I tested, so:
Reviewed-by: Stefano Garzarella <sgarzare@...hat.com>
Thanks,
Stefano
>
> Changes in v2:
> Avoid the duplication of code in v1.
> Also fix virtio socket code.
>
>
> Changes in v3:
> Use "lock_sock_nested(sk, level);" -- suggested by Stefano.
> Add Stefano's Tested-by.
>
> net/vmw_vsock/af_vsock.c | 16 ++++++++++++----
> net/vmw_vsock/hyperv_transport.c | 2 +-
> net/vmw_vsock/virtio_transport_common.c | 2 +-
> 3 files changed, 14 insertions(+), 6 deletions(-)
>
> diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c
> index ab47bf3ab66e..2ab43b2bba31 100644
> --- a/net/vmw_vsock/af_vsock.c
> +++ b/net/vmw_vsock/af_vsock.c
> @@ -638,7 +638,7 @@ struct sock *__vsock_create(struct net *net,
> }
> EXPORT_SYMBOL_GPL(__vsock_create);
>
> -static void __vsock_release(struct sock *sk)
> +static void __vsock_release(struct sock *sk, int level)
> {
> if (sk) {
> struct sk_buff *skb;
> @@ -648,9 +648,17 @@ static void __vsock_release(struct sock *sk)
> vsk = vsock_sk(sk);
> pending = NULL; /* Compiler warning. */
>
> + /* The release call is supposed to use lock_sock_nested()
> + * rather than lock_sock(), if a sock lock should be acquired.
> + */
> transport->release(vsk);
>
> - lock_sock(sk);
> + /* When "level" is SINGLE_DEPTH_NESTING, use the nested
> + * version to avoid the warning "possible recursive locking
> + * detected". When "level" is 0, lock_sock_nested(sk, level)
> + * is the same as lock_sock(sk).
> + */
> + lock_sock_nested(sk, level);
> sock_orphan(sk);
> sk->sk_shutdown = SHUTDOWN_MASK;
>
> @@ -659,7 +667,7 @@ static void __vsock_release(struct sock *sk)
>
> /* Clean up any sockets that never were accepted. */
> while ((pending = vsock_dequeue_accept(sk)) != NULL) {
> - __vsock_release(pending);
> + __vsock_release(pending, SINGLE_DEPTH_NESTING);
> sock_put(pending);
> }
>
> @@ -708,7 +716,7 @@ EXPORT_SYMBOL_GPL(vsock_stream_has_space);
>
> static int vsock_release(struct socket *sock)
> {
> - __vsock_release(sock->sk);
> + __vsock_release(sock->sk, 0);
> sock->sk = NULL;
> sock->state = SS_FREE;
>
> diff --git a/net/vmw_vsock/hyperv_transport.c b/net/vmw_vsock/hyperv_transport.c
> index 261521d286d6..c443db7af8d4 100644
> --- a/net/vmw_vsock/hyperv_transport.c
> +++ b/net/vmw_vsock/hyperv_transport.c
> @@ -559,7 +559,7 @@ static void hvs_release(struct vsock_sock *vsk)
> struct sock *sk = sk_vsock(vsk);
> bool remove_sock;
>
> - lock_sock(sk);
> + lock_sock_nested(sk, SINGLE_DEPTH_NESTING);
> remove_sock = hvs_close_lock_held(vsk);
> release_sock(sk);
> if (remove_sock)
> diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c
> index 5bb70c692b1e..a666ef8fc54e 100644
> --- a/net/vmw_vsock/virtio_transport_common.c
> +++ b/net/vmw_vsock/virtio_transport_common.c
> @@ -820,7 +820,7 @@ void virtio_transport_release(struct vsock_sock *vsk)
> struct sock *sk = &vsk->sk;
> bool remove_sock = true;
>
> - lock_sock(sk);
> + lock_sock_nested(sk, SINGLE_DEPTH_NESTING);
> if (sk->sk_type == SOCK_STREAM)
> remove_sock = virtio_transport_close(vsk);
>
> --
> 2.19.1
>
--
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