linux-kernel - [PATCH 2/5] exec: Directly call security_bprm_set_creds from __do_execve

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Date:   Sat, 09 May 2020 14:41:17 -0500
From:   ebiederm@...ssion.com (Eric W. Biederman)
To:     <linux-kernel@...r.kernel.org>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Oleg Nesterov <oleg@...hat.com>, Jann Horn <jannh@...gle.com>,
        Kees Cook <keescook@...omium.org>,
        Greg Ungerer <gerg@...ux-m68k.org>,
        Rob Landley <rob@...dley.net>,
        Bernd Edlinger <bernd.edlinger@...mail.de>,
        <linux-fsdevel@...r.kernel.org>, Al Viro <viro@...IV.linux.org.uk>,
        Alexey Dobriyan <adobriyan@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Casey Schaufler <casey@...aufler-ca.com>,
        linux-security-module@...r.kernel.org,
        James Morris <jmorris@...ei.org>,
        "Serge E. Hallyn" <serge@...lyn.com>,
        Andy Lutomirski <luto@...capital.net>
Subject: [PATCH 2/5] exec: Directly call security_bprm_set_creds from __do_execve_file


Now that security_bprm_set_creds is no longer responsible for calling
cap_bprm_set_creds, security_bprm_set_creds only does something for
the primary file that is being executed (not any interpreters it may
have).  Therefore call security_bprm_set_creds from __do_execve_file,
instead of from prepare_binprm so that it is only called once, and
remove the now unnecessary called_set_creds field of struct binprm.

Signed-off-by: "Eric W. Biederman" <ebiederm@...ssion.com>
---
 fs/exec.c                  | 11 +++++------
 include/linux/binfmts.h    |  6 ------
 security/apparmor/domain.c |  3 ---
 security/selinux/hooks.c   |  2 --
 security/smack/smack_lsm.c |  3 ---
 security/tomoyo/tomoyo.c   |  6 ------
 6 files changed, 5 insertions(+), 26 deletions(-)

diff --git a/fs/exec.c b/fs/exec.c
index 765bfd51a546..635b5085050c 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -1635,12 +1635,6 @@ int prepare_binprm(struct linux_binprm *bprm)
 
 	bprm_fill_uid(bprm);
 
-	/* fill in binprm security blob */
-	retval = security_bprm_set_creds(bprm);
-	if (retval)
-		return retval;
-	bprm->called_set_creds = 1;
-
 	retval = cap_bprm_set_creds(bprm);
 	if (retval)
 		return retval;
@@ -1858,6 +1852,11 @@ static int __do_execve_file(int fd, struct filename *filename,
 	if (retval < 0)
 		goto out;
 
+	/* fill in binprm security blob */
+	retval = security_bprm_set_creds(bprm);
+	if (retval)
+		goto out;
+
 	retval = prepare_binprm(bprm);
 	if (retval < 0)
 		goto out;
diff --git a/include/linux/binfmts.h b/include/linux/binfmts.h
index 1b48e2154766..42f760acfc2c 100644
--- a/include/linux/binfmts.h
+++ b/include/linux/binfmts.h
@@ -26,12 +26,6 @@ struct linux_binprm {
 	unsigned long p; /* current top of mem */
 	unsigned long argmin; /* rlimit marker for copy_strings() */
 	unsigned int
-		/*
-		 * True after the bprm_set_creds hook has been called once
-		 * (multiple calls can be made via prepare_binprm() for
-		 * binfmt_script/misc).
-		 */
-		called_set_creds:1,
 		/*
 		 * True if most recent call to the commoncaps bprm_set_creds
 		 * hook (due to multiple prepare_binprm() calls from the
diff --git a/security/apparmor/domain.c b/security/apparmor/domain.c
index 6ceb74e0f789..61b9181a9e1f 100644
--- a/security/apparmor/domain.c
+++ b/security/apparmor/domain.c
@@ -875,9 +875,6 @@ int apparmor_bprm_set_creds(struct linux_binprm *bprm)
 		file_inode(bprm->file)->i_mode
 	};
 
-	if (bprm->called_set_creds)
-		return 0;
-
 	ctx = task_ctx(current);
 	AA_BUG(!cred_label(bprm->cred));
 	AA_BUG(!ctx);
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index 0b4e32161b77..ff3e1be53da5 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);
diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
index 8c61d175e195..bd1967730fec 100644
--- a/security/smack/smack_lsm.c
+++ b/security/smack/smack_lsm.c
@@ -904,9 +904,6 @@ static int smack_bprm_set_creds(struct linux_binprm *bprm)
 	struct superblock_smack *sbsp;
 	int rc;
 
-	if (bprm->called_set_creds)
-		return 0;
-
 	isp = smack_inode(inode);
 	if (isp->smk_task == NULL || isp->smk_task == bsp->smk_task)
 		return 0;
diff --git a/security/tomoyo/tomoyo.c b/security/tomoyo/tomoyo.c
index 716c92ec941a..d965ce80a7fb 100644
--- a/security/tomoyo/tomoyo.c
+++ b/security/tomoyo/tomoyo.c
@@ -71,12 +71,6 @@ static void tomoyo_bprm_committed_creds(struct linux_binprm *bprm)
  */
 static int tomoyo_bprm_set_creds(struct linux_binprm *bprm)
 {
-	/*
-	 * Do only if this function is called for the first time of an execve
-	 * operation.
-	 */
-	if (bprm->called_set_creds)
-		return 0;
 	/*
 	 * Load policy if /sbin/tomoyo-init exists and /sbin/init is requested
 	 * for the first time.
-- 
2.25.0