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[198.145.64.163]) by smtp.gmail.com with ESMTPSA id s13sm138380pfh.118.2020.05.19.11.10.13 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 19 May 2020 11:10:13 -0700 (PDT) Date: Tue, 19 May 2020 11:10:12 -0700 From: Kees Cook To: "Eric W. Biederman" Cc: linux-kernel@vger.kernel.org, Linus Torvalds , Oleg Nesterov , Jann Horn , Greg Ungerer , Rob Landley , Bernd Edlinger , linux-fsdevel@vger.kernel.org, Al Viro , Alexey Dobriyan , Andrew Morton , Casey Schaufler , linux-security-module@vger.kernel.org, James Morris , "Serge E. Hallyn" , Andy Lutomirski Subject: Re: [PATCH v2 2/8] exec: Factor security_bprm_creds_for_exec out of security_bprm_set_creds Message-ID: <202005191108.7A6E97831@keescook> References: <87h7wujhmz.fsf@x220.int.ebiederm.org> <87sgga6ze4.fsf@x220.int.ebiederm.org> <87v9l4zyla.fsf_-_@x220.int.ebiederm.org> <877dx822er.fsf_-_@x220.int.ebiederm.org> <87v9kszrzh.fsf_-_@x220.int.ebiederm.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87v9kszrzh.fsf_-_@x220.int.ebiederm.org> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, May 18, 2020 at 07:30:10PM -0500, Eric W. Biederman wrote: > > Today security_bprm_set_creds has several implementations: > apparmor_bprm_set_creds, cap_bprm_set_creds, selinux_bprm_set_creds, > smack_bprm_set_creds, and tomoyo_bprm_set_creds. > > Except for cap_bprm_set_creds they all test bprm->called_set_creds and > return immediately if it is true. The function cap_bprm_set_creds > ignores bprm->calld_sed_creds entirely. > > Create a new LSM hook security_bprm_creds_for_exec that is called just > before prepare_binprm in __do_execve_file, resulting in a LSM hook > that is called exactly once for the entire of exec. Modify the bits > of security_bprm_set_creds that only want to be called once per exec > into security_bprm_creds_for_exec, leaving only cap_bprm_set_creds > behind. > > Remove bprm->called_set_creds all of it's former users have been moved > to security_bprm_creds_for_exec. > > Add or upate comments a appropriate to bring them up to date and > to reflect this change. Yup, awesome. One nit below. Reviewed-by: Kees Cook > [...] > diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c > index 0b4e32161b77..718345dd76bb 100644 > --- a/security/selinux/hooks.c > +++ b/security/selinux/hooks.c > [...] > @@ -2297,8 +2297,6 @@ static int selinux_bprm_set_creds(struct linux_binprm *bprm) > > /* SELinux context only depends on initial program or script and not > * the script interpreter */ > - if (bprm->called_set_creds) > - return 0; > > old_tsec = selinux_cred(current_cred()); > new_tsec = selinux_cred(bprm->cred); As you've done in the other LSMs, I think this comment can be removed (or moved to the top of the function) too. -- Kees Cook