linux-kernel - Re: [PATCH v18 01/15] Add PR_{GET,SET}_NO_NEW_PRIVS to prevent execve from granting privs

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Message-ID: <CAObL_7ER32AesD6bHk591ss0hTFmp0bjVOKV9oEdhiFwCEVOBA@mail.gmail.com>
Date:	Thu, 12 Apr 2012 21:25:27 -0700
From:	Andrew Lutomirski <luto@....edu>
To:	James Morris <jmorris@...ei.org>
Cc:	Will Drewry <wad@...omium.org>, linux-kernel@...r.kernel.org,
	linux-man@...r.kernel.org, linux-security-module@...r.kernel.org,
	linux-arch@...r.kernel.org, linux-doc@...r.kernel.org,
	kernel-hardening@...ts.openwall.com, netdev@...r.kernel.org,
	x86@...nel.org, arnd@...db.de,
	"David S. Miller" <davem@...emloft.net>, hpa@...or.com,
	mingo@...hat.com, Oleg Nesterov <oleg@...hat.com>,
	peterz@...radead.org, rdunlap@...otime.net, mcgrathr@...omium.org,
	tglx@...utronix.de, Eric Paris <eparis@...hat.com>,
	Serge Hallyn <serge.hallyn@...onical.com>, djm@...drot.org,
	scarybeasts@...il.com, indan@....nu, pmoore@...hat.com,
	Andrew Morton <akpm@...ux-foundation.org>,
	Jonathan Corbet <corbet@....net>, eric.dumazet@...il.com,
	markus@...omium.org, coreyb@...ux.vnet.ibm.com,
	Kees Cook <keescook@...omium.org>,
	Andy Lutomirski <luto@...capital.net>,
	Stephen Smalley <sds@...ho.nsa.gov>
Subject: Re: [PATCH v18 01/15] Add PR_{GET,SET}_NO_NEW_PRIVS to prevent execve
 from granting privs

On Thu, Apr 12, 2012 at 9:16 PM, James Morris <jmorris@...ei.org> wrote:
> On Thu, 12 Apr 2012, Will Drewry wrote:
>> diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
>> index d85b793..0b06685 100644
>> --- a/security/selinux/hooks.c
>> +++ b/security/selinux/hooks.c
>> @@ -2016,6 +2016,13 @@ static int selinux_bprm_set_creds(struct linux_binprm *bprm)
>>               new_tsec->sid = old_tsec->exec_sid;
>>               /* Reset exec SID on execve. */
>>               new_tsec->exec_sid = 0;
>> +
>> +             /*
>> +              * Minimize confusion: if no_new_privs and a transition is
>> +              * explicitly requested, then fail the exec.
>> +              */
>> +             if (bprm->unsafe & LSM_UNSAFE_NO_NEW_PRIVS)
>> +                     return -EPERM;
>>       } else {
>>               /* Check for a default transition on this program. */
>>               rc = security_transition_sid(old_tsec->sid, isec->sid,
>> @@ -2029,7 +2036,8 @@ static int selinux_bprm_set_creds(struct linux_binprm *bprm)
>>       ad.selinux_audit_data = &sad;
>>       ad.u.path = bprm->file->f_path;
>>
>> -     if (bprm->file->f_path.mnt->mnt_flags & MNT_NOSUID)
>> +     if ((bprm->file->f_path.mnt->mnt_flags & MNT_NOSUID) ||
>> +         (bprm->unsafe & LSM_UNSAFE_NO_NEW_PRIVS))
>>               new_tsec->sid = old_tsec->sid;
>>
>>       if (new_tsec->sid == old_tsec->sid) {
>> --
>
> What about dynamic transitions in SELinux ?
>

What's a dynamic transition?

--Andy
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