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SubjectRe: [PATCH, local root on 2.4, 2.6?] compute_creds race
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Andy Lutomirski <luto@stanford.edu> writes:

> Olaf Dietsche wrote:
>
>> Andy Lutomirski <luto@myrealbox.com> writes:
>>
>>>The setuid program is now running with uid=euid=500 but full permitted
>>>capabilities. There are two (or three) ways to effectively get local
>>>root now:
>> What about this slightly shorter fix?
>> diff -urN a/fs/exec.c b/fs/exec.c
>> --- a/fs/exec.c Fri Mar 12 01:19:06 2004
>> +++ b/fs/exec.c Sat Apr 10 10:54:20 2004
>> @@ -942,6 +942,9 @@
>> if(!capable(CAP_SETUID)) {
>> bprm->e_uid = current->uid;
>> bprm->e_gid = current->gid;
>> + cap_clear (bprm->cap_inheritable);
>> + cap_clear (bprm->cap_permitted);
>> + cap_clear (bprm->cap_effective);
>> }
>> }
>> }
>
> This makes the bprm_compute_creds hook even less sane than now
> (i.e. it assumes that all LSMs will work like the current capability
> modules). The hook should allow LSM to change this functionality
> without reintroducing the race. For example, it breaks my work on
> fixing capabilities.

This patch fixes the problem without moving and renaming huge amounts
of code. And the hook is still in place, so I don't see your problems.

If you look at the code - as seen in 2.4 and early 2.5 - that's (more
or less) the place where the fix should be.

Anyway, I don't really object against moving code around.

Regards, Olaf.
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