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

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Date:	Fri, 13 Apr 2012 14:16:20 +1000 (EST)
From:	James Morris <jmorris@...ei.org>
To:	Will Drewry <wad@...omium.org>
cc:	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, luto@....edu, 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, 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 ?


- James
-- 
James Morris
<jmorris@...ei.org>
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