access() system call

Pawel S. Veselov (vps@unicorn.niimm.spb.su)
Sun, 8 Feb 1998 23:38:18 +0300 (MSK)

Hello, All !

I found strange behavior for access() system call :

compiling and executing this program

------------------
#include <stdio.h>
#include <unistd.h>

void main(void)
{
setreuid(1224,0);
printf("reuid=%d,euid=%d\n",getuid(),geteuid());
if ((access("/vmlinuz",R_OK | W_OK))<0)
perror("access");
if ((chmod("/dev/ttyS0",0600))<0)
perror("chmod");
setreuid(0,1224);
printf("reuid=%d,euid=%d\n",getuid(),geteuid());
if ((access("/vmlinuz",R_OK | W_OK))<0)
perror("access");
if ((chmod("/dev/ttyS0",0600))<0)
perror("chmod");

}
------------------

gives following results :

------------------

[root@unicorn]/home/vps/c# ./tuid
reuid=1224,euid=0
access: Permission denied
reuid=0,euid=1224
chmod: Operation not permitted
[root@unicorn]/home/vps/c# ls -la /vmlinuz
-rw-r--r-- 1 root root 374386 Jan 24 01:29 /vmlinuz
[root@unicorn]/home/vps/c# ls -ls /dev/ttyS1
0 crw------- 1 uucp uucp 4, 65 Feb 8 22:37 /dev/ttyS1
[root@unicorn]/home/vps/c#

------------------

How can I read/write /vmlinuz but can't chmod() (I am not root) and why can
I chmod() but can't access r/w /vmlinux ( I am real root at this )

Any suggestions ?

Bye.

--
You know you have a small apartment when Rice Krispies echo.
		-- S. Rickly Christian



--
    With best of best regards, Pawel S. Veselov (aka Black Angel)
       internet : vps@unicorn.niimm.spb.su ( mail,finger,talk )
                 Web page : http://www.niimm.spb.su/~vps/
			    ICQ : 5252265


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