linux-kernel - Re: epoll_create(0) becomes not to fail (Re: issue with epoll system call)

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Message-ID: <feaf5ed90905121758o161c204dncafa46cebdd9c24b@mail.gmail.com>
Date:	Wed, 13 May 2009 09:58:27 +0900
From:	Hiroyuki Machida <Hiroyuki.Mach@...il.com>
To:	rohit verma <rohit.170309@...il.com>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: epoll_create(0) becomes not to fail (Re: issue with epoll system 
	call)

Hi
I think it's better to read, before submitting report/patch

http://kernelnewbies.org/FoundBug
http://kernelnewbies.org/UpstreamMerge/SubmittingPatches

----
Hiroyuki Machida



On Tue, May 12, 2009 at 3:54 PM, rohit verma <rohit.170309@...il.com> wrote:
> hi,
>
> I have created a patch for epoll_create syscall as shown below. Plz
> have a check and
> get back to me.
>
> diff a/fs/eventpoll.c   b/fs/eventpoll.c
>
>
>
> --- eventpoll_orig.c    2009-05-12 12:07:27.000000000 +0530
> +++ eventpoll.c 2009-05-12 12:10:14.000000000 +0530
> @@ -1136,7 +1136,7 @@
>  SYSCALL_DEFINE1(epoll_create, int, size)
>  {
> -       if (size < 0)
> +       if (size <= 0)
>                 return -EINVAL;
>         return sys_epoll_create1(0);
>
>
>
> Since there might be some formatting problems, i'm also attaching the
> patch in this
> mail.
>
> Regards,
> Rohit
>
>
>
> On Fri, May 8, 2009 at 1:19 PM, Hiroyuki Machida
> <Hiroyuki.Mach@...il.com> wrote:
>>
>> Hi  Verma,
>>
>> I think your point is right. but descriptions looks not straight forward.
>> And title of the message is very confusable.
>> I think descriptions like following would be easy to understand, and
>> you should attach a your signed-off patch to fix the bug.
>>
>>
>> Thanks,
>> Hiro
>>
>> ----
>>
>> The following patch changed behavior of epoll_create(0);
>>
>> http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commitdiff;h=9fe5ad9c8cef9ad5873d8ee55d1cf00d9b607df0;hp=e38b36f325153eaadd1c2a7abc5762079233e540
>>
>>
>> Before applying the patch,
>> sys_epoll_create2(int size, int flags)
>> returned -EINVAL,  with size=0;
>>
>> But,  if-condtion which is introduced in sys_epoll_create() by this patch,
>> looks to fail to consider case of size==0 as follows;
>>
>>  asmlinkage long sys_epoll_create(int size)
>>  {
>> -       return sys_epoll_create2(size, 0);
>> +       if (size < 0)
>> +               return -EINVAL;
>> +
>> +       return sys_epoll_create1(0);
>>  }
>>
>>
>> ---
>> Hiroyuki Machida
>>
>>
>>
>> On Thu, May 7, 2009 at 4:10 PM, rohit verma <rohit.170309@...il.com> wrote:
>> > hi all,
>> >
>> > The man pages of epoll_create says - "Since Linux 2.6.8, the size
>> > argument is unused.  (The kernel dynamically sizes the required data
>> > structures without needing this initial hint.)" .
>> >
>> > Also, it says that the syscall returns EINVAL , when size is not
>> > positive. (i.e For, any value greater than 0, the kernel dynamically
>> > sizes the required data stuctures). When size is zero or less than
>> > zero, it has to return with error as EINVAL.
>> >
>> > the link:  http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commitdiff;h=9fe5ad9c8cef9ad5873d8ee55d1cf00d9b607df0;hp=e38b36f325153eaadd1c2a7abc5762079233e540
>> >
>> > shows the latest patch of the epoll syscall. here , the syscall says:
>> >
>> > asmlinkage long sys_epoll_create(int size)
>> > {
>> > - return sys_epoll_create2(size,0);
>> > + if (size < 0)
>> > +  return -EINVAL;
>> > +
>> > +return sys_epoll_create1(0);
>> > }
>> >
>> > So if size = 0, it returns success which might not be the expected
>> > result. So i feel that the condition check should be
>> > " if (size <= 0) ". could u please check on this and reply me..
>> >
>> > Thank you,
>> >
>> > Regards,
>> > rohit
>> > --
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>> >
>
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