Re: [PATCH] usb: gadget: f_fs: initialize reset_work at allocation time

["Peter Chen (CIX)" <peter.chen@kernel.org>]

On 26-06-09 15:36:34, Tyler Baker wrote:
> ffs_fs_kill_sb() unconditionally calls cancel_work_sync() on
> ffs->reset_work when a functionfs instance is unmounted:
> 
> 	ffs_data_reset(ffs);
> 	cancel_work_sync(&ffs->reset_work);
> 
> However ffs->reset_work is only ever initialized via INIT_WORK() in
> ffs_func_set_alt() and ffs_func_disable(), and only on the
> FFS_DEACTIVATED path. That state is reached solely by ffs_data_closed()
> when the instance is mounted with the "no_disconnect" option, so for the
> common case (no "no_disconnect", or mounted and unmounted without ever
> being deactivated) reset_work is never initialized.
> 
> ffs_data_new() allocates the ffs_data with kzalloc_obj() and does not
> initialize reset_work, and ffs_data_reset()/ffs_data_clear() do not touch
> it either, so reset_work.func is left NULL. cancel_work_sync() on such a
> work then trips the WARN_ON(!work->func) guard in __flush_work():
> 
>   WARNING: kernel/workqueue.c:4301 at __flush_work+0x330/0x360, CPU#3: umount
>   Call trace:
>    __flush_work
>    cancel_work_sync
>    ffs_fs_kill_sb [usb_f_fs]
>    deactivate_locked_super
>    deactivate_super
>    cleanup_mnt
>    __cleanup_mnt
>    task_work_run
>    exit_to_user_mode_loop
>    el0_svc
> 
> On older kernels cancel_work_sync() on a zero-initialized work struct was
> a silent no-op, which hid the missing initialization.
> 
> Initialize reset_work once in ffs_data_new() so it is always valid for
> the lifetime of the ffs_data, and drop the now-redundant INIT_WORK()
> calls from the two deactivation paths.
> 
> Fixes: 18d6b32fca38 ("usb: gadget: f_fs: add "no_disconnect" mode")
> Cc: stable@vger.kernel.org
> Signed-off-by: Tyler Baker <tyler.baker@oss.qualcomm.com>
> Cc: Loic Poulain <loic.poulain@oss.qualcomm.com>
> Cc: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
> Cc: Srinivas Kandagatla <srinivas.kandagatla@oss.qualcomm.com>

Reviewed-by: Peter Chen <peter.chen@kernel.org>

Peter
> ---
>  drivers/usb/gadget/function/f_fs.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/usb/gadget/function/f_fs.c b/drivers/usb/gadget/function/f_fs.c
> index 75912ce6ab55..1ee21e29ef73 100644
> --- a/drivers/usb/gadget/function/f_fs.c
> +++ b/drivers/usb/gadget/function/f_fs.c
> @@ -288,6 +288,7 @@ static int ffs_acquire_dev(const char *dev_name, struct ffs_data *ffs_data);
>  static void ffs_release_dev(struct ffs_dev *ffs_dev);
>  static int ffs_ready(struct ffs_data *ffs);
>  static void ffs_closed(struct ffs_data *ffs);
> +static void ffs_reset_work(struct work_struct *work);
>  
>  /* Misc helper functions ****************************************************/
>  
> @@ -2221,6 +2222,7 @@ static struct ffs_data *ffs_data_new(const char *dev_name)
>  	init_waitqueue_head(&ffs->ev.waitq);
>  	init_waitqueue_head(&ffs->wait);
>  	init_completion(&ffs->ep0req_completion);
> +	INIT_WORK(&ffs->reset_work, ffs_reset_work);
>  
>  	/* XXX REVISIT need to update it in some places, or do we? */
>  	ffs->ev.can_stall = 1;
> @@ -3775,7 +3777,6 @@ static int ffs_func_set_alt(struct usb_function *f,
>  	if (ffs->state == FFS_DEACTIVATED) {
>  		ffs->state = FFS_CLOSING;
>  		spin_unlock_irqrestore(&ffs->eps_lock, flags);
> -		INIT_WORK(&ffs->reset_work, ffs_reset_work);
>  		schedule_work(&ffs->reset_work);
>  		return -ENODEV;
>  	}
> @@ -3806,7 +3807,6 @@ static void ffs_func_disable(struct usb_function *f)
>  	if (ffs->state == FFS_DEACTIVATED) {
>  		ffs->state = FFS_CLOSING;
>  		spin_unlock_irqrestore(&ffs->eps_lock, flags);
> -		INIT_WORK(&ffs->reset_work, ffs_reset_work);
>  		schedule_work(&ffs->reset_work);
>  		return;
>  	}
> -- 
> 2.43.0
> 
> 

-- 

Best regards,
Peter