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References: <20220927095813.v2.1.Ia168b651a69b253059f2bbaa60b98083e619545c@changeid>
In-Reply-To: <20220927095813.v2.1.Ia168b651a69b253059f2bbaa60b98083e619545c@changeid>
From:   Luiz Augusto von Dentz <luiz.dentz@gmail.com>
Date:   Wed, 28 Sep 2022 12:31:52 -0700
Message-ID: <CABBYNZJkzQfWu_xhtubn=030fi+XLGSx9wMamEMUg8Ly2jpPGg@mail.gmail.com>
Subject: Re: [PATCH v2] Bluetooth: Prevent double register of suspend
To:     Abhishek Pandit-Subedi <abhishekpandit@google.com>
Cc:     linux-bluetooth@vger.kernel.org,
        Abhishek Pandit-Subedi <abhishekpandit@chromium.org>,
        syzbot <syzkaller@googlegroups.com>,
        "David S. Miller" <davem@davemloft.net>,
        Eric Dumazet <edumazet@google.com>,
        Jakub Kicinski <kuba@kernel.org>,
        Johan Hedberg <johan.hedberg@gmail.com>,
        Marcel Holtmann <marcel@holtmann.org>,
        Paolo Abeni <pabeni@redhat.com>, linux-kernel@vger.kernel.org,
        netdev@vger.kernel.org
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

Hi Abhishek,

On Tue, Sep 27, 2022 at 9:58 AM Abhishek Pandit-Subedi
<abhishekpandit@google.com> wrote:
>
> From: Abhishek Pandit-Subedi <abhishekpandit@chromium.org>
>
> Suspend notifier should only be registered and unregistered once per
> hdev. Simplify this by only registering during driver registration and
> simply exiting early when HCI_USER_CHANNEL is set.
>
> Reported-by: syzbot <syzkaller@googlegroups.com>
> Fixes: 359ee4f834f5 (Bluetooth: Unregister suspend with userchannel)
> Signed-off-by: Abhishek Pandit-Subedi <abhishekpandit@chromium.org>
> ---
> This is fixing a syzbot reported warning. Tested in the following ways:
> * Normal start-up of driver with bluez.
> * Start/stop loop using HCI_USER_CHANNEL (sock path).
> * USB reset triggering hci_dev_unregister (driver path).
>
> ------------[ cut here ]------------
> double register detected
> WARNING: CPU: 0 PID: 2657 at kernel/notifier.c:27
> notifier_chain_register kernel/notifier.c:27 [inline]
> WARNING: CPU: 0 PID: 2657 at kernel/notifier.c:27
> notifier_chain_register+0x5c/0x124 kernel/notifier.c:22
> Modules linked in:
> CPU: 0 PID: 2657 Comm: syz-executor212 Not tainted
> 5.10.136-syzkaller-19376-g6f46a5fe0124 #0
>     8f0771607702f5ef7184d2ee33bd0acd70219fc4
>     Hardware name: Google Google Compute Engine/Google Compute Engine,
>     BIOS Google 07/22/2022
>     RIP: 0010:notifier_chain_register kernel/notifier.c:27 [inline]
>     RIP: 0010:notifier_chain_register+0x5c/0x124 kernel/notifier.c:22
>     Code: 6a 41 00 4c 8b 23 4d 85 e4 0f 84 88 00 00 00 e8 c2 1e 19 00 49
>     39 ec 75 18 e8 b8 1e 19 00 48 c7 c7 80 6d ca 84 e8 2c 68 48 03 <0f> 0b
>         e9 af 00 00 00 e8 a0 1e 19 00 48 8d 7d 10 48 89 f8 48 c1 e8
>         RSP: 0018:ffffc900009d7da8 EFLAGS: 00010286
>         RAX: 0000000000000000 RBX: ffff8881076fd1d8 RCX: 0000000000000000
>         RDX: 0000001810895100 RSI: ffff888110895100 RDI: fffff5200013afa7
>         RBP: ffff88811a4191d0 R08: ffffffff813b8ca1 R09: 0000000080000000
>         R10: 0000000000000000 R11: 0000000000000005 R12: ffff88811a4191d0
>         R13: dffffc0000000000 R14: 0000000000000000 R15: 0000000000000000
>         FS: 00005555571f5300(0000) GS:ffff8881f6c00000(0000)
>         knlGS:0000000000000000
>         CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>         CR2: 000078e3857f3075 CR3: 000000010d668000 CR4: 00000000003506f0
>         DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
>         DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
>         Call Trace:
>         blocking_notifier_chain_register+0x8c/0xa6 kernel/notifier.c:254
>         hci_register_suspend_notifier net/bluetooth/hci_core.c:2733
>         [inline]
>         hci_register_suspend_notifier+0x6b/0x7c
>         net/bluetooth/hci_core.c:2727
>         hci_sock_release+0x270/0x3cf net/bluetooth/hci_sock.c:889
>         __sock_release+0xcd/0x1de net/socket.c:597
>         sock_close+0x18/0x1c net/socket.c:1267
>         __fput+0x418/0x729 fs/file_table.c:281
>         task_work_run+0x12b/0x15b kernel/task_work.c:151
>         tracehook_notify_resume include/linux/tracehook.h:188 [inline]
>         exit_to_user_mode_loop kernel/entry/common.c:165 [inline]
>         exit_to_user_mode_prepare+0x8f/0x130 kernel/entry/common.c:192
>         syscall_exit_to_user_mode+0x172/0x1b2 kernel/entry/common.c:268
>         entry_SYSCALL_64_after_hwframe+0x61/0xc6
>         RIP: 0033:0x78e38575e1db
>         Code: 0f 05 48 3d 00 f0 ff ff 77 45 c3 0f 1f 40 00 48 83 ec 18 89
>         7c 24 0c e8 63 fc ff ff 8b 7c 24 0c 41 89 c0 b8 03 00 00 00 0f 05
>         <48> 3d 00 f0 ff ff 77 35 44 89 c7 89 44 24 0c e8 a1 fc ff ff 8b 44
>         RSP: 002b:00007ffffc20a0b0 EFLAGS: 00000293 ORIG_RAX:
>         0000000000000003
>         RAX: 0000000000000000 RBX: 0000000000000006 RCX: 000078e38575e1db
>         RDX: ffffffffffffffb8 RSI: 0000000020000000 RDI: 0000000000000005
>         RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000150
>         R10: 0000000000000000 R11: 0000000000000293 R12: 000000000000e155
>         R13: 00007ffffc20a140 R14: 00007ffffc20a130 R15: 00007ffffc20a0e8
>
> Changes in v2:
> - Removed suspend registration from hci_sock.
> - Exit hci_suspend_notifier early if user channel.
>
>  net/bluetooth/hci_core.c | 4 ++++
>  net/bluetooth/hci_sock.c | 3 ---
>  2 files changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/net/bluetooth/hci_core.c b/net/bluetooth/hci_core.c
> index 66c7cdba0d32..86ce2dd1c7fb 100644
> --- a/net/bluetooth/hci_core.c
> +++ b/net/bluetooth/hci_core.c
> @@ -2406,6 +2406,10 @@ static int hci_suspend_notifier(struct notifier_block *nb, unsigned long action,
>                 container_of(nb, struct hci_dev, suspend_notifier);
>         int ret = 0;
>
> +       /* Userspace has full control of this device. Do nothing. */
> +       if (hci_dev_test_flag(hdev, HCI_USER_CHANNEL))
> +               return NOTIFY_DONE;
> +
>         if (action == PM_SUSPEND_PREPARE)
>                 ret = hci_suspend_dev(hdev);
>         else if (action == PM_POST_SUSPEND)
> diff --git a/net/bluetooth/hci_sock.c b/net/bluetooth/hci_sock.c
> index b2a33a05c93e..06581223238c 100644
> --- a/net/bluetooth/hci_sock.c
> +++ b/net/bluetooth/hci_sock.c
> @@ -887,7 +887,6 @@ static int hci_sock_release(struct socket *sock)
>                          */
>                         hci_dev_do_close(hdev);
>                         hci_dev_clear_flag(hdev, HCI_USER_CHANNEL);
> -                       hci_register_suspend_notifier(hdev);
>                         mgmt_index_added(hdev);
>                 }
>
> @@ -1216,7 +1215,6 @@ static int hci_sock_bind(struct socket *sock, struct sockaddr *addr,
>                 }
>
>                 mgmt_index_removed(hdev);
> -               hci_unregister_suspend_notifier(hdev);
>
>                 err = hci_dev_open(hdev->id);
>                 if (err) {
> @@ -1231,7 +1229,6 @@ static int hci_sock_bind(struct socket *sock, struct sockaddr *addr,
>                                 err = 0;
>                         } else {
>                                 hci_dev_clear_flag(hdev, HCI_USER_CHANNEL);
> -                               hci_register_suspend_notifier(hdev);
>                                 mgmt_index_added(hdev);
>                                 hci_dev_put(hdev);
>                                 goto done;
> --
> 2.37.3.998.g577e59143f-goog
>

Looks like our CI got stuck for some reason, do you mind sending a v3
just to confirm nothing breaks with these changes?

-- 
Luiz Augusto von Dentz