linux-kernel - how to get right euid?

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Message-ID: <78aa970c1001020516m3d2255fj38f02629e7d740c8@mail.gmail.com>
Date:	Sat, 2 Jan 2010 21:16:42 +0800
From:	Kevin Qu <rofail@...il.com>
To:	dhowells@...hat.com, linux-kernel@...r.kernel.org
Subject: how to get right euid?

I wrote a kernel module and it create a "file" in /proc.
The "file" permission is set to 644.
When check access permission, I use :

if( op == 4 || (op ==2 && current->euid == 0) )
        return 0;

But it does not work on 2.6.29,
so I changed it like below:

if( op & 0x4 || (op & 0x2 && current_euid() == 0) )
        return 0;

It works when read from the "file" in /proc,
but when write to it with sudo, like:

sudo echo "some thing" > /proc/my_file

It denied. (But it works when I su to superuser and do so.)

So I checked the current_euid(),
but it returns 1000 (not 0),Why?

Thanks for help.

Rofail Qu
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