hfsplus: honor setgid flag on directories

When creating a file inside a directory that has the setgid flag set, give
the new file the group ID of the parent, and also the setgid flag if it is
a directory itself.

Link: http://lkml.kernel.org/r/20171204192705.GA6101@debian.home
Signed-off-by: Ernesto A. Fernandez <ernesto.mnd.fernandez@gmail.com>
Reviewed-by: Vyacheslav Dubeyko <slava@dubeyko.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/hfsplus/dir.c

@@ -444,7 +444,7 @@ static int hfsplus_symlink(struct inode *dir, struct dentry *dentry,
 	int res = -ENOMEM;
 
 	mutex_lock(&sbi->vh_mutex);
-	inode = hfsplus_new_inode(dir->i_sb, S_IFLNK | S_IRWXUGO);
+	inode = hfsplus_new_inode(dir->i_sb, dir, S_IFLNK | S_IRWXUGO);
 	if (!inode)
 		goto out;
 
@@ -486,7 +486,7 @@ static int hfsplus_mknod(struct inode *dir, struct dentry *dentry,
 	int res = -ENOMEM;
 
 	mutex_lock(&sbi->vh_mutex);
-	inode = hfsplus_new_inode(dir->i_sb, mode);
+	inode = hfsplus_new_inode(dir->i_sb, dir, mode);
 	if (!inode)
 		goto out;
 

fs/hfsplus/hfsplus_fs.h

@@ -478,7 +478,8 @@ extern const struct address_space_operations hfsplus_aops;
 extern const struct address_space_operations hfsplus_btree_aops;
 extern const struct dentry_operations hfsplus_dentry_operations;
 
-struct inode *hfsplus_new_inode(struct super_block *sb, umode_t mode);
+struct inode *hfsplus_new_inode(struct super_block *sb, struct inode *dir,
+				umode_t mode);
 void hfsplus_delete_inode(struct inode *inode);
 void hfsplus_inode_read_fork(struct inode *inode,
 			     struct hfsplus_fork_raw *fork);

fs/hfsplus/inode.c

@@ -354,7 +354,8 @@ static const struct file_operations hfsplus_file_operations = {
 	.unlocked_ioctl = hfsplus_ioctl,
 };
 
-struct inode *hfsplus_new_inode(struct super_block *sb, umode_t mode)
+struct inode *hfsplus_new_inode(struct super_block *sb, struct inode *dir,
+				umode_t mode)
 {
 	struct hfsplus_sb_info *sbi = HFSPLUS_SB(sb);
 	struct inode *inode = new_inode(sb);
@@ -364,9 +365,7 @@ struct inode *hfsplus_new_inode(struct super_block *sb, umode_t mode)
 		return NULL;
 
 	inode->i_ino = sbi->next_cnid++;
-	inode->i_mode = mode;
-	inode->i_uid = current_fsuid();
-	inode->i_gid = current_fsgid();
+	inode_init_owner(inode, dir, mode);
 	set_nlink(inode, 1);
 	inode->i_mtime = inode->i_atime = inode->i_ctime = current_time(inode);
 

fs/hfsplus/super.c

@@ -549,7 +549,7 @@ static int hfsplus_fill_super(struct super_block *sb, void *data, int silent)
 
 		if (!sbi->hidden_dir) {
 			mutex_lock(&sbi->vh_mutex);
-			sbi->hidden_dir = hfsplus_new_inode(sb, S_IFDIR);
+			sbi->hidden_dir = hfsplus_new_inode(sb, root, S_IFDIR);
 			if (!sbi->hidden_dir) {
 				mutex_unlock(&sbi->vh_mutex);
 				err = -ENOMEM;