SELinux: Abstract use of cred security blob

Don't use the cred->security pointer directly.
Provide a helper function that provides the security blob pointer.
Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
[kees: adjusted for ordered init series]
Signed-off-by: Kees Cook <keescook@chromium.org>

security/selinux/hooks.c

@@ -226,7 +226,7 @@ static inline u32 cred_sid(const struct cred *cred)
 {
 	const struct task_security_struct *tsec;
 
-	tsec = cred->security;
+	tsec = selinux_cred(cred);
 	return tsec->sid;
 }
 
@@ -498,7 +498,7 @@ static int may_context_mount_sb_relabel(u32 sid,
 			struct superblock_security_struct *sbsec,
 			const struct cred *cred)
 {
-	const struct task_security_struct *tsec = cred->security;
+	const struct task_security_struct *tsec = selinux_cred(cred);
 	int rc;
 
 	rc = avc_has_perm(&selinux_state,
@@ -517,7 +517,7 @@ static int may_context_mount_inode_relabel(u32 sid,
 			struct superblock_security_struct *sbsec,
 			const struct cred *cred)
 {
-	const struct task_security_struct *tsec = cred->security;
+	const struct task_security_struct *tsec = selinux_cred(cred);
 	int rc;
 	rc = avc_has_perm(&selinux_state,
 			  tsec->sid, sbsec->sid, SECCLASS_FILESYSTEM,
@@ -1803,7 +1803,7 @@ static int may_create(struct inode *dir,
 		      struct dentry *dentry,
 		      u16 tclass)
 {
-	const struct task_security_struct *tsec = current_security();
+	const struct task_security_struct *tsec = selinux_cred(current_cred());
 	struct inode_security_struct *dsec;
 	struct superblock_security_struct *sbsec;
 	u32 sid, newsid;
@@ -1825,7 +1825,7 @@ static int may_create(struct inode *dir,
 	if (rc)
 		return rc;
 
-	rc = selinux_determine_inode_label(current_security(), dir,
+	rc = selinux_determine_inode_label(selinux_cred(current_cred()), dir,
 					   &dentry->d_name, tclass, &newsid);
 	if (rc)
 		return rc;
@@ -2332,8 +2332,8 @@ static int selinux_bprm_set_creds(struct linux_binprm *bprm)
 	if (bprm->called_set_creds)
 		return 0;
 
-	old_tsec = current_security();
-	new_tsec = bprm->cred->security;
+	old_tsec = selinux_cred(current_cred());
+	new_tsec = selinux_cred(bprm->cred);
 	isec = inode_security(inode);
 
 	/* Default to the current task SID. */
@@ -2497,7 +2497,7 @@ static void selinux_bprm_committing_creds(struct linux_binprm *bprm)
 	struct rlimit *rlim, *initrlim;
 	int rc, i;
 
-	new_tsec = bprm->cred->security;
+	new_tsec = selinux_cred(bprm->cred);
 	if (new_tsec->sid == new_tsec->osid)
 		return;
 
@@ -2540,7 +2540,7 @@ static void selinux_bprm_committing_creds(struct linux_binprm *bprm)
  */
 static void selinux_bprm_committed_creds(struct linux_binprm *bprm)
 {
-	const struct task_security_struct *tsec = current_security();
+	const struct task_security_struct *tsec = selinux_cred(current_cred());
 	struct itimerval itimer;
 	u32 osid, sid;
 	int rc, i;
@@ -2777,7 +2777,7 @@ static int selinux_dentry_init_security(struct dentry *dentry, int mode,
 	u32 newsid;
 	int rc;
 
-	rc = selinux_determine_inode_label(current_security(),
+	rc = selinux_determine_inode_label(selinux_cred(current_cred()),
 					   d_inode(dentry->d_parent), name,
 					   inode_mode_to_security_class(mode),
 					   &newsid);
@@ -2797,14 +2797,14 @@ static int selinux_dentry_create_files_as(struct dentry *dentry, int mode,
 	int rc;
 	struct task_security_struct *tsec;
 
-	rc = selinux_determine_inode_label(old->security,
+	rc = selinux_determine_inode_label(selinux_cred(old),
 					   d_inode(dentry->d_parent), name,
 					   inode_mode_to_security_class(mode),
 					   &newsid);
 	if (rc)
 		return rc;
 
-	tsec = new->security;
+	tsec = selinux_cred(new);
 	tsec->create_sid = newsid;
 	return 0;
 }
@@ -2814,7 +2814,7 @@ static int selinux_inode_init_security(struct inode *inode, struct inode *dir,
 				       const char **name,
 				       void **value, size_t *len)
 {
-	const struct task_security_struct *tsec = current_security();
+	const struct task_security_struct *tsec = selinux_cred(current_cred());
 	struct superblock_security_struct *sbsec;
 	u32 newsid, clen;
 	int rc;
@@ -2824,7 +2824,7 @@ static int selinux_inode_init_security(struct inode *inode, struct inode *dir,
 
 	newsid = tsec->create_sid;
 
-	rc = selinux_determine_inode_label(current_security(),
+	rc = selinux_determine_inode_label(selinux_cred(current_cred()),
 		dir, qstr,
 		inode_mode_to_security_class(inode->i_mode),
 		&newsid);
@@ -3286,7 +3286,7 @@ static int selinux_inode_copy_up(struct dentry *src, struct cred **new)
 			return -ENOMEM;
 	}
 
-	tsec = new_creds->security;
+	tsec = selinux_cred(new_creds);
 	/* Get label from overlay inode and set it in create_sid */
 	selinux_inode_getsecid(d_inode(src), &sid);
 	tsec->create_sid = sid;
@@ -3706,7 +3706,7 @@ static int selinux_cred_alloc_blank(struct cred *cred, gfp_t gfp)
  */
 static void selinux_cred_free(struct cred *cred)
 {
-	struct task_security_struct *tsec = cred->security;
+	struct task_security_struct *tsec = selinux_cred(cred);
 
 	/*
 	 * cred->security == NULL if security_cred_alloc_blank() or
@@ -3726,7 +3726,7 @@ static int selinux_cred_prepare(struct cred *new, const struct cred *old,
 	const struct task_security_struct *old_tsec;
 	struct task_security_struct *tsec;
 
-	old_tsec = old->security;
+	old_tsec = selinux_cred(old);
 
 	tsec = kmemdup(old_tsec, sizeof(struct task_security_struct), gfp);
 	if (!tsec)
@@ -3741,8 +3741,8 @@ static int selinux_cred_prepare(struct cred *new, const struct cred *old,
  */
 static void selinux_cred_transfer(struct cred *new, const struct cred *old)
 {
-	const struct task_security_struct *old_tsec = old->security;
-	struct task_security_struct *tsec = new->security;
+	const struct task_security_struct *old_tsec = selinux_cred(old);
+	struct task_security_struct *tsec = selinux_cred(new);
 
 	*tsec = *old_tsec;
 }
@@ -3758,7 +3758,7 @@ static void selinux_cred_getsecid(const struct cred *c, u32 *secid)
  */
 static int selinux_kernel_act_as(struct cred *new, u32 secid)
 {
-	struct task_security_struct *tsec = new->security;
+	struct task_security_struct *tsec = selinux_cred(new);
 	u32 sid = current_sid();
 	int ret;
 
@@ -3783,7 +3783,7 @@ static int selinux_kernel_act_as(struct cred *new, u32 secid)
 static int selinux_kernel_create_files_as(struct cred *new, struct inode *inode)
 {
 	struct inode_security_struct *isec = inode_security(inode);
-	struct task_security_struct *tsec = new->security;
+	struct task_security_struct *tsec = selinux_cred(new);
 	u32 sid = current_sid();
 	int ret;
 
@@ -4332,7 +4332,7 @@ static int sock_has_perm(struct sock *sk, u32 perms)
 static int selinux_socket_create(int family, int type,
 				 int protocol, int kern)
 {
-	const struct task_security_struct *tsec = current_security();
+	const struct task_security_struct *tsec = selinux_cred(current_cred());
 	u32 newsid;
 	u16 secclass;
 	int rc;
@@ -4352,7 +4352,7 @@ static int selinux_socket_create(int family, int type,
 static int selinux_socket_post_create(struct socket *sock, int family,
 				      int type, int protocol, int kern)
 {
-	const struct task_security_struct *tsec = current_security();
+	const struct task_security_struct *tsec = selinux_cred(current_cred());
 	struct inode_security_struct *isec = inode_security_novalidate(SOCK_INODE(sock));
 	struct sk_security_struct *sksec;
 	u16 sclass = socket_type_to_security_class(family, type, protocol);
@@ -5233,7 +5233,7 @@ static int selinux_secmark_relabel_packet(u32 sid)
 	const struct task_security_struct *__tsec;
 	u32 tsid;
 
-	__tsec = current_security();
+	__tsec = selinux_cred(current_cred());
 	tsid = __tsec->sid;
 
 	return avc_has_perm(&selinux_state,
@@ -6170,7 +6170,7 @@ static int selinux_getprocattr(struct task_struct *p,
 	unsigned len;
 
 	rcu_read_lock();
-	__tsec = __task_cred(p)->security;
+	__tsec = selinux_cred(__task_cred(p));
 
 	if (current != p) {
 		error = avc_has_perm(&selinux_state,
@@ -6293,7 +6293,7 @@ static int selinux_setprocattr(const char *name, void *value, size_t size)
 	   operation.  See selinux_bprm_set_creds for the execve
 	   checks and may_create for the file creation checks. The
 	   operation will then fail if the context is not permitted. */
-	tsec = new->security;
+	tsec = selinux_cred(new);
 	if (!strcmp(name, "exec")) {
 		tsec->exec_sid = sid;
 	} else if (!strcmp(name, "fscreate")) {
@@ -6422,7 +6422,7 @@ static int selinux_key_alloc(struct key *k, const struct cred *cred,
 	if (!ksec)
 		return -ENOMEM;
 
-	tsec = cred->security;
+	tsec = selinux_cred(cred);
 	if (tsec->keycreate_sid)
 		ksec->sid = tsec->keycreate_sid;
 	else

security/selinux/include/objsec.h

@@ -158,4 +158,9 @@ struct bpf_security_struct {
 	u32 sid;  /*SID of bpf obj creater*/
 };
 
+static inline struct task_security_struct *selinux_cred(const struct cred *cred)
+{
+	return cred->security;
+}
+
 #endif /* _SELINUX_OBJSEC_H_ */

security/selinux/xfrm.c

@@ -79,7 +79,7 @@ static int selinux_xfrm_alloc_user(struct xfrm_sec_ctx **ctxp,
 				   gfp_t gfp)
 {
 	int rc;
-	const struct task_security_struct *tsec = current_security();
+	const struct task_security_struct *tsec = selinux_cred(current_cred());
 	struct xfrm_sec_ctx *ctx = NULL;
 	u32 str_len;
 
@@ -138,7 +138,7 @@ static void selinux_xfrm_free(struct xfrm_sec_ctx *ctx)
  */
 static int selinux_xfrm_delete(struct xfrm_sec_ctx *ctx)
 {
-	const struct task_security_struct *tsec = current_security();
+	const struct task_security_struct *tsec = selinux_cred(current_cred());
 
 	if (!ctx)
 		return 0;