lkml.org 
[lkml]   [2016]   [Dec]   [5]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] kernel/sysctl: return -EINVAL if write invalid val to ulong type sysctl
On 2016/12/3 3:24, Eric W. Biederman wrote:

> Yisheng Xie <xieyisheng1@huawei.com> writes:
>
>> On 2016/12/1 5:33, Andrew Morton wrote:
>>> On Wed, 30 Nov 2016 18:30:52 +0800 Yisheng Xie <xieyisheng1@huawei.com> wrote:
>>>
>>>> I tried to echo an invalid value to an unsigned long type sysctl on
>>>> 4.9.0-rc6:
>>>> linux:~# cat /proc/sys/vm/user_reserve_kbytes
>>>> 131072
>>>> linux:~# echo -1 > /proc/sys/vm/user_reserve_kbytes
>>>> linux:~# cat /proc/sys/vm/user_reserve_kbytes
>>>> 131072
>>>>
>>>> The echo operation got error and the value do not write to
>>>> user_reserve_kbytes, however, user do not know it until checking
>>>> the value again.
>>>>
>>>> This patch return -EINVAL when write an invalid value to unsigned
>>>> long type sysctl to make user know what happened without
>>>> checking its value once more, just as what proc_douintvec do.
>>>
>>> hmpf.
>>>
>>> # echo 18446744073709551615 > /proc/sys/vm/user_reserve_kbytes
>>> # cat /proc/sys/vm/user_reserve_kbytes
>>> 18446744073709551615
>>>
>>> I think that when taking in an unsigned long the kernel should simply
>>> treat -1 as 0xffffffff (or 0xffffffffffffffff). It's natural and
>>> normal and everyone knows what it means?
>>>
>> Hi Andrew,
>> Thank you for your reply.
>> Do you means it should be like this:
>> # echo -1 > /proc/sys/vm/user_reserve_kbytes
>> # cat /proc/sys/vm/user_reserve_kbytes
>> 18446744073709551615
>>
>> I looks ok to me, however, I not sure whether other code in the kernel
>> will also use its complement if user write a negative number for an
>> unsigned long. Does anyone have other opinion ?
>
> Largely we need to be very careful with changing these functions as
> they have been around for a long time, and have a very diverse set of
> users.
>
> So while changes are possible a reasonable argument needs to be made
> that nothing in userspace cares.
>
> Eric
>

Hi Eric,

This patch is aimed to change the return value if write invalid value to
ulong type sysctl, just to keep the same as int type sysctl.

Thanks,
Xishi Qiu

> .
>



\
 
 \ /
  Last update: 2016-12-05 07:14    [W:0.047 / U:0.088 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site