suid bit behaviour modification in 2.6.0-test5

[Jean-pierre Cartal]

Hello,

I'm running a standard RH 9 installation upgraded to kernel 2.6.0-test5 
with rpms from http://people.redhat.com/arjanv/2.5/RPMS.kernel/.

I noticed that contrary to what was happening with 2.4.x kernel, suid 
root files don't loose their suid bit when they get overwritten by a 
normal user (see example below)

Is this the intended behaviour or a bug ?

Example :

[cartaljp@localhost test]$ uname -r
2.6.0-0.test5.1.38
[cartaljp@localhost test]$ id
uid=500(cartaljp) gid=500(cartaljp)
[cartaljp@localhost test]$ touch suid_test
[cartaljp@localhost test]$ ls -l
total 0
-rw-rw-r--    1 cartaljp cartaljp        0 Sep 19 07:55 suid_test
[cartaljp@localhost test]$ su -
Password:
[root@localhost test]# chown root ~cartaljp/test/suid_test
[root@localhost test]# chmod 4775 ~cartaljp/test/suid_test
[root@localhost test]# exit
[cartaljp@localhost test]$ ls -l
total 0
-rwsrwxr-x    1 root     cartaljp        0 Sep 19 07:55 suid_test
[cartaljp@localhost test]$ cp /bin/ls suid_test
[cartaljp@localhost test]$ ls -l
total 72
-rwsrwxr-x    1 root     cartaljp    67668 Sep 19 07:56 suid_test <- 
Suid bit is still set whereas with 2.4.x kernel it was reset.

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