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Subject: Re: [PATCH] fs: proc: fix error return code of
 proc_map_files_readdir()
To:     Alexey Dobriyan <adobriyan@gmail.com>,
        Eric Biggers <ebiggers@kernel.org>
Cc:     christian@brauner.io, ebiederm@xmission.com,
        akpm@linux-foundation.org, keescook@chromium.org,
        gladkov.alexey@gmail.com, walken@google.com,
        bernd.edlinger@hotmail.de, avagin@gmail.com, deller@gmx.de,
        linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org
References: <20210309095527.27969-1-baijiaju1990@gmail.com>
 <YEe+v+ywMrxgmj05@gmail.com> <YEfG54xMM7OtPEE5@localhost.localdomain>
From:   Jia-Ju Bai <baijiaju1990@gmail.com>
Message-ID: <86f9dae2-7bb1-4555-44a4-24045260916b@gmail.com>
Date:   Wed, 10 Mar 2021 09:11:50 +0800
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On 2021/3/10 3:05, Alexey Dobriyan wrote:
> On Tue, Mar 09, 2021 at 10:30:23AM -0800, Eric Biggers wrote:
>
>>> --- a/fs/proc/base.c
>>> +++ b/fs/proc/base.c
>>> @@ -2332,8 +2332,10 @@ proc_map_files_readdir(struct file *file, struct dir_context *ctx)
>>>   		goto out_put_task;
>>>   
>>>   	mm = get_task_mm(task);
>>> -	if (!mm)
>>> +	if (!mm) {
>>> +		ret = -ENOENT;
>>>   		goto out_put_task;
>>> +	}
>>>   
>>>   	ret = mmap_read_lock_killable(mm);
>> Is there something in particular that makes you think that returning ENOENT is
>> the correct behavior in this case?  Try 'ls /proc/$pid/map_files' where pid is a
>> kernel thread; it's an empty directory, which is probably intentional.  Your
>> patch would change reading the directory to fail with ENOENT.
> Yes. 0 from readdir means "no more stuff", not an error.

Thanks for your reply and explanation.
I am sorry for the false report...


Best wishes,
Jia-Ju Bai