linux-kernel - Re: [PATCH 24/43] userns: Convert ptrace, kill, set_priority permission checks to work with kuids and kgids

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Date:	Fri, 20 Apr 2012 16:51:00 -0700
From:	ebiederm@...ssion.com (Eric W. Biederman)
To:	"Serge E. Hallyn" <serge@...lyn.com>
Cc:	linux-kernel@...r.kernel.org,
	Linux Containers <containers@...ts.linux-foundation.org>,
	Cyrill Gorcunov <gorcunov@...nvz.org>,
	linux-security-module@...r.kernel.org,
	Al Viro <viro@...IV.linux.org.uk>,
	linux-fsdevel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [PATCH 24/43] userns: Convert ptrace, kill, set_priority permission checks to work with kuids and kgids

"Serge E. Hallyn" <serge@...lyn.com> writes:

> Quoting Eric W. Beiderman (ebiederm@...ssion.com):
>> From: Eric W. Biederman <ebiederm@...ssion.com>
>> 
>> Update the permission checks to use the new uid_eq and gid_eq helpers
>> and remove the now unnecessary user_ns equality comparison.
>> 
>> Signed-off-by: Eric W. Biederman <ebiederm@...ssion.com>
>> ---

>> @@ -1389,10 +1388,8 @@ static int kill_as_cred_perm(const struct cred *cred,
>>  			     struct task_struct *target)
>>  {
>>  	const struct cred *pcred = __task_cred(target);
>> -	if (cred->user_ns != pcred->user_ns)
>> -		return 0;
>> -	if (cred->euid != pcred->suid && cred->euid != pcred->uid &&
>> -	    cred->uid  != pcred->suid && cred->uid  != pcred->uid)
>> +	if (uid_eq(cred->euid, pcred->suid) && uid_eq(cred->euid, pcred->uid) &&
>
> These should be !uid_eq() right?
>> +	    uid_eq(cred->uid,  pcred->suid) && uid_eq(cred->uid,
>pcred->uid))

Yes.

Thank you for catching this.  This kind of mistake is unfortunately much
to easy to make.

Eric
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