Merge tag 'selinux-pr-20190305' of git://git.kernel.org/pub/scm/linux/kernel/git/pcmoore/selinux

Pull SELinux updates from Paul Moore:
 "Nine SELinux patches for v5.1, all bug fixes.

  As far as I'm concerned, nothing really jumps out as risky or special
  to me, but each commit has a decent description so you can judge for
  yourself. As usual, everything passes the selinux-testsuite; please
  merge for v5.1"

* tag 'selinux-pr-20190305' of git://git.kernel.org/pub/scm/linux/kernel/git/pcmoore/selinux:
  selinux: fix avc audit messages
  selinux: replace BUG_ONs with WARN_ONs in avc.c
  selinux: log invalid contexts in AVCs
  selinux: replace some BUG_ON()s with a WARN_ON()
  selinux: inline some AVC functions used only once
  selinux: do not override context on context mounts
  selinux: never allow relabeling on context mounts
  selinux: stop passing MAY_NOT_BLOCK to the AVC upon follow_link
  selinux: avoid silent denials in permissive mode under RCU walk

security/selinux/hooks.c

@@ -490,16 +490,10 @@ static int may_context_mount_inode_relabel(u32 sid,
 	return rc;
 }
 
-static int selinux_is_sblabel_mnt(struct super_block *sb)
+static int selinux_is_genfs_special_handling(struct super_block *sb)
 {
-	struct superblock_security_struct *sbsec = sb->s_security;
-
-	return sbsec->behavior == SECURITY_FS_USE_XATTR ||
-		sbsec->behavior == SECURITY_FS_USE_TRANS ||
-		sbsec->behavior == SECURITY_FS_USE_TASK ||
-		sbsec->behavior == SECURITY_FS_USE_NATIVE ||
-		/* Special handling. Genfs but also in-core setxattr handler */
-		!strcmp(sb->s_type->name, "sysfs") ||
+	/* Special handling. Genfs but also in-core setxattr handler */
+	return	!strcmp(sb->s_type->name, "sysfs") ||
 		!strcmp(sb->s_type->name, "pstore") ||
 		!strcmp(sb->s_type->name, "debugfs") ||
 		!strcmp(sb->s_type->name, "tracefs") ||
@@ -509,6 +503,34 @@ static int selinux_is_sblabel_mnt(struct super_block *sb)
 		  !strcmp(sb->s_type->name, "cgroup2")));
 }
 
+static int selinux_is_sblabel_mnt(struct super_block *sb)
+{
+	struct superblock_security_struct *sbsec = sb->s_security;
+
+	/*
+	 * IMPORTANT: Double-check logic in this function when adding a new
+	 * SECURITY_FS_USE_* definition!
+	 */
+	BUILD_BUG_ON(SECURITY_FS_USE_MAX != 7);
+
+	switch (sbsec->behavior) {
+	case SECURITY_FS_USE_XATTR:
+	case SECURITY_FS_USE_TRANS:
+	case SECURITY_FS_USE_TASK:
+	case SECURITY_FS_USE_NATIVE:
+		return 1;
+
+	case SECURITY_FS_USE_GENFS:
+		return selinux_is_genfs_special_handling(sb);
+
+	/* Never allow relabeling on context mounts */
+	case SECURITY_FS_USE_MNTPOINT:
+	case SECURITY_FS_USE_NONE:
+	default:
+		return 0;
+	}
+}
+
 static int sb_finish_set_opts(struct super_block *sb)
 {
 	struct superblock_security_struct *sbsec = sb->s_security;
@@ -2881,9 +2903,8 @@ static int selinux_inode_follow_link(struct dentry *dentry, struct inode *inode,
 	if (IS_ERR(isec))
 		return PTR_ERR(isec);
 
-	return avc_has_perm_flags(&selinux_state,
-				  sid, isec->sid, isec->sclass, FILE__READ, &ad,
-				  rcu ? MAY_NOT_BLOCK : 0);
+	return avc_has_perm(&selinux_state,
+			    sid, isec->sid, isec->sclass, FILE__READ, &ad);
 }
 
 static noinline int audit_inode_permission(struct inode *inode,
@@ -2938,7 +2959,9 @@ static int selinux_inode_permission(struct inode *inode, int mask)
 		return PTR_ERR(isec);
 
 	rc = avc_has_perm_noaudit(&selinux_state,
-				  sid, isec->sid, isec->sclass, perms, 0, &avd);
+				  sid, isec->sid, isec->sclass, perms,
+				  (flags & MAY_NOT_BLOCK) ? AVC_NONBLOCKING : 0,
+				  &avd);
 	audited = avc_audit_required(perms, &avd, rc,
 				     from_access ? FILE__AUDIT_ACCESS : 0,
 				     &denied);
@@ -3197,12 +3220,16 @@ static int selinux_inode_setsecurity(struct inode *inode, const char *name,
 				     const void *value, size_t size, int flags)
 {
 	struct inode_security_struct *isec = inode_security_novalidate(inode);
+	struct superblock_security_struct *sbsec = inode->i_sb->s_security;
 	u32 newsid;
 	int rc;
 
 	if (strcmp(name, XATTR_SELINUX_SUFFIX))
 		return -EOPNOTSUPP;
 
+	if (!(sbsec->flags & SBLABEL_MNT))
+		return -EOPNOTSUPP;
+
 	if (!value || !size)
 		return -EACCES;
 
@@ -6236,7 +6263,10 @@ static void selinux_inode_invalidate_secctx(struct inode *inode)
  */
 static int selinux_inode_notifysecctx(struct inode *inode, void *ctx, u32 ctxlen)
 {
-	return selinux_inode_setsecurity(inode, XATTR_SELINUX_SUFFIX, ctx, ctxlen, 0);
+	int rc = selinux_inode_setsecurity(inode, XATTR_SELINUX_SUFFIX,
+					   ctx, ctxlen, 0);
+	/* Do not return error when suppressing label (SBLABEL_MNT not set). */
+	return rc == -EOPNOTSUPP ? 0 : rc;
 }
 
 /*