zpl_inode.c: Fix SMACK interoperability

 closes: #11646

 ref: #11646 (comment)
 ref: cschaufler/smack-next#1

  SMACK needs to have the ZFS dentry security field setup before SMACK's
    d_instantiate() hook is called as it requires functioning
    '__vfs_getxattr()' calls to properly set the labels.

  Fixes:
  1) file instantiation properly setting the object label to the
     subject's label
  2) proper file labelling in a transmutable directory

  Functions Updated:
  1) zpl_create()
  2) zpl_mknod()
  3) zpl_mkdir()
  4) zpl_symlink()

Signed-off-by: TerraTech <[email protected]>

Author: TerraTech

include/os/linux/zfs/sys/zpl.h

@@ -52,6 +52,7 @@ extern const struct file_operations zpl_dir_file_operations;
 
 /* zpl_super.c */
 extern void zpl_prune_sb(int64_t nr_to_scan, void *arg);
+extern void zpl_inode_destroy(struct inode *ip);
 
 extern const struct super_operations zpl_super_operations;
 extern const struct export_operations zpl_export_operations;

module/os/linux/zfs/zpl_inode.c

@@ -149,14 +149,16 @@ zpl_create(struct inode *dir, struct dentry *dentry, umode_t mode, bool flag)
 	error = -zfs_create(ITOZ(dir), dname(dentry), vap, 0,
 	    mode, &zp, cr, 0, NULL);
 	if (error == 0) {
-		d_instantiate(dentry, ZTOI(zp));
-
 		error = zpl_xattr_security_init(ZTOI(zp), dir, &dentry->d_name);
 		if (error == 0)
 			error = zpl_init_acl(ZTOI(zp), dir);
 
-		if (error)
+		if (error) {
 			(void) zfs_remove(ITOZ(dir), dname(dentry), cr, 0);
+			zpl_inode_destroy(ZTOI(zp));
+		} else {
+			d_instantiate(dentry, ZTOI(zp));
+		}
 	}
 
 	spl_fstrans_unmark(cookie);
@@ -198,14 +200,16 @@ zpl_mknod(struct inode *dir, struct dentry *dentry, umode_t mode,
 	error = -zfs_create(ITOZ(dir), dname(dentry), vap, 0,
 	    mode, &zp, cr, 0, NULL);
 	if (error == 0) {
-		d_instantiate(dentry, ZTOI(zp));
-
 		error = zpl_xattr_security_init(ZTOI(zp), dir, &dentry->d_name);
 		if (error == 0)
 			error = zpl_init_acl(ZTOI(zp), dir);
 
-		if (error)
+		if (error) {
 			(void) zfs_remove(ITOZ(dir), dname(dentry), cr, 0);
+			zpl_inode_destroy(ZTOI(zp));
+		} else {
+			d_instantiate(dentry, ZTOI(zp));
+		}
 	}
 
 	spl_fstrans_unmark(cookie);
@@ -308,14 +312,16 @@ zpl_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)
 	cookie = spl_fstrans_mark();
 	error = -zfs_mkdir(ITOZ(dir), dname(dentry), vap, &zp, cr, 0, NULL);
 	if (error == 0) {
-		d_instantiate(dentry, ZTOI(zp));
-
 		error = zpl_xattr_security_init(ZTOI(zp), dir, &dentry->d_name);
 		if (error == 0)
 			error = zpl_init_acl(ZTOI(zp), dir);
 
-		if (error)
+		if (error) {
 			(void) zfs_rmdir(ITOZ(dir), dname(dentry), NULL, cr, 0);
+			zpl_inode_destroy(ZTOI(zp));
+		} else {
+			d_instantiate(dentry, ZTOI(zp));
+		}
 	}
 
 	spl_fstrans_unmark(cookie);
@@ -488,11 +494,13 @@ zpl_symlink(struct inode *dir, struct dentry *dentry, const char *name)
 	error = -zfs_symlink(ITOZ(dir), dname(dentry), vap,
 	    (char *)name, &zp, cr, 0);
 	if (error == 0) {
-		d_instantiate(dentry, ZTOI(zp));
-
 		error = zpl_xattr_security_init(ZTOI(zp), dir, &dentry->d_name);
-		if (error)
+		if (error) {
 			(void) zfs_remove(ITOZ(dir), dname(dentry), cr, 0);
+			zpl_inode_destroy(ZTOI(zp));
+		} else {
+			d_instantiate(dentry, ZTOI(zp));
+		}
 	}
 
 	spl_fstrans_unmark(cookie);

module/os/linux/zfs/zpl_super.c

@@ -41,7 +41,7 @@ zpl_inode_alloc(struct super_block *sb)
 	return (ip);
 }
 
-static void
+void
 zpl_inode_destroy(struct inode *ip)
 {
 	ASSERT(atomic_read(&ip->i_count) == 0);