No Read Up No Write Down

[Mohammad zoroufi]

Dear All,
After switching on SELinux in MLS enforcing mode, I'd like to know how the
slogan of "no read up, no write

down" works.
I created some text files with the following descriptions
TestFile_S0        system_u:object_r:usr_t:s0
TestFile_S0C2   system_u:object_r:usr_t:s0:c2
TestFile_S1        system_u:object_r:usr_t:s1
TestFile_S2        system_u:object_r:usr_t:s2
TestFile_S2C11  system_u:object_r:usr_t:s2:c11
TestFile_S2C5    system_u:object_r:usr_t:s2:c5
TestFile_S3         system_u:object_r:usr_t:s3
TestFile_S3C14   system_u:object_r:usr_t:s3:c14
TestFile_S3C5     system_u:object_r:usr_t:s3:c5
After creating these text file, I went to create users having different
security clearance;
The clearance of each created user is listed bellow:

*Login Name    SELinux User        Role            MLS/MCS Range*
first                    x_first                xguest_r                s0
second               x_second           sysadm_r       s3-s3:c5.c15
third                   x_third               sysadm_r
s1:c3.c15-s3:c5.c10
forth                   x_forth               system_r
s1-s1:c0.c10
root                    root                   system_r
s0-s15:c0.c1023

having the clearance delegated for each user I expect user first have read
write access to TestFile_S0 and just
write access to all other files; user second have read access to files such
as TestFile_S0, TestFile_S0C2,
TestFile_S2, TestFile_S2C5, TestFile_S2C11 and only write access to
TestFile_S3, TestFile_S3C14.
when I switch to MLS enforcing mode I see something else.
These users have no permission to write to files they expect they have write
access to.
I'd like to know the where this problem originates
Moreover when user first wants to take a list of the directory contents only
TestFile_S0, TestFile_S1,
TestFile_S2 are listed not else; user second sees TestFile_S0, TestFile_S1,
TestFile2, TestFile3; users
third and root sees all files; user forth sees just TestFile_S0 not more.
I don't know why such lists are taken when I'd like to take a list.
Any comment is wellcome

Best Regards
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://listman.redhat.com/archives/fedora-selinux-list/attachments/20090423/e74ee4ad/attachment.htm>