linux-kernel - Re: [PATCH V1] fuse: Set fuse request error upon fuse abort connection

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Date:   Mon, 10 May 2021 13:22:23 +0530
From:   pragalla@...eaurora.org
To:     miklos@...redi.hu
Cc:     stummala@...eaurora.org, linux-kernel@...r.kernel.org,
        linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH V1] fuse: Set fuse request error upon fuse abort
 connection

Hi Miklos,

Did you get a chance to look on the below change ?
could you please review and provide your comments if any.

Thanks and Regards,
Pradeep

On 2021-04-16 19:49, Pradeep P V K wrote:
> There is a minor race in setting the fuse out request error
> between fuse_abort_conn() and fuse_dev_do_read() as explained
> below.
> 
> Thread-1			  Thread-2
> ========			  ========
> ->fuse_simple_request()           ->shutdown
>   ->__fuse_request_send()
>     ->queue_request()		->fuse_abort_conn()
> ->fuse_dev_do_read()                ->acquire(fpq->lock)
>   ->wait_for(fpq->lock) 	  ->set err to all req's in fpq->io
> 				  ->release(fpq->lock)
>   ->acquire(fpq->lock)
>   ->add req to fpq->io
> 
> The above scenario may cause Thread-1 request to add into
> fpq->io list after Thread-2 sets -ECONNABORTED err to all
> its requests in fpq->io list. This leaves Thread-1 request
> with unset err and this further misleads as a completed
> request without an err set upon request_end().
> 
> Handle this by setting the err appropriately.
> 
> Signed-off-by: Pradeep P V K <pragalla@...eaurora.org>
> ---
>  fs/fuse/dev.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c
> index a5ceccc..102c56f 100644
> --- a/fs/fuse/dev.c
> +++ b/fs/fuse/dev.c
> @@ -1283,6 +1283,7 @@ static ssize_t fuse_dev_do_read(struct fuse_dev
> *fud, struct file *file,
>  	clear_bit(FR_LOCKED, &req->flags);
>  	if (!fpq->connected) {
>  		err = fc->aborted ? -ECONNABORTED : -ENODEV;
> +		req->out.h.error = err;
>  		goto out_end;
>  	}
>  	if (err) {