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    Subject[PATCH 5.10 076/188] usbip: synchronize event handler with sysfs code paths
    Date
    From: Shuah Khan <skhan@linuxfoundation.org>

    commit 363eaa3a450abb4e63bd6e3ad79d1f7a0f717814 upstream.

    Fuzzing uncovered race condition between sysfs code paths in usbip
    drivers. Device connect/disconnect code paths initiated through
    sysfs interface are prone to races if disconnect happens during
    connect and vice versa.

    Use sysfs_lock to synchronize event handler with sysfs paths
    in usbip drivers.

    Cc: stable@vger.kernel.org
    Reported-and-tested-by: syzbot+a93fba6d384346a761e3@syzkaller.appspotmail.com
    Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>
    Link: https://lore.kernel.org/r/c5c8723d3f29dfe3d759cfaafa7dd16b0dfe2918.1616807117.git.skhan@linuxfoundation.org
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    drivers/usb/usbip/usbip_event.c | 2 ++
    1 file changed, 2 insertions(+)

    --- a/drivers/usb/usbip/usbip_event.c
    +++ b/drivers/usb/usbip/usbip_event.c
    @@ -70,6 +70,7 @@ static void event_handler(struct work_st
    while ((ud = get_event()) != NULL) {
    usbip_dbg_eh("pending event %lx\n", ud->event);

    + mutex_lock(&ud->sysfs_lock);
    /*
    * NOTE: shutdown must come first.
    * Shutdown the device.
    @@ -90,6 +91,7 @@ static void event_handler(struct work_st
    ud->eh_ops.unusable(ud);
    unset_event(ud, USBIP_EH_UNUSABLE);
    }
    + mutex_unlock(&ud->sysfs_lock);

    wake_up(&ud->eh_waitq);
    }

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