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Re: [PATCH] kernel/sysctl: return -EINVAL if write invalid val to ulong type sysctl

From Andrew Morton <akpm@linux-foundation.org>
Newsgroups linux.kernel
Subject Re: [PATCH] kernel/sysctl: return -EINVAL if write invalid val to ulong type sysctl
Date 2016-11-30 22:40 +0100
Message-ID <sJkLD-2XW-7@gated-at.bofh.it> (permalink)
References <sJasW-4VL-9@gated-at.bofh.it>
Organization linux.* mail to news gateway

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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?

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Thread

[PATCH] kernel/sysctl: return -EINVAL if write invalid val to ulong type sysctl Yisheng Xie <xieyisheng1@huawei.com> - 2016-11-30 11:40 +0100
  Re: [PATCH] kernel/sysctl: return -EINVAL if write invalid val to  ulong type sysctl Andrew Morton <akpm@linux-foundation.org> - 2016-11-30 22:40 +0100
    Re: [PATCH] kernel/sysctl: return -EINVAL if write invalid val to  ulong type sysctl Yisheng Xie <xieyisheng1@huawei.com> - 2016-12-02 08:00 +0100
      Re: [PATCH] kernel/sysctl: return -EINVAL if write invalid val to ulong type sysctl ebiederm@xmission.com (Eric W. Biederman) - 2016-12-02 20:30 +0100
        Re: [PATCH] kernel/sysctl: return -EINVAL if write invalid val to  ulong type sysctl Xishi Qiu <qiuxishi@huawei.com> - 2016-12-05 07:20 +0100
        Re: [PATCH] kernel/sysctl: return -EINVAL if write invalid val to  ulong type sysctl Yisheng Xie <xieyisheng1@huawei.com> - 2016-12-06 14:00 +0100

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