pstore: inode: Use __free(pstore_iput) for inode allocations

Simplify error path for failures where "inode" needs to be freed.

Cc: Guilherme G. Piccoli <gpiccoli@igalia.com>
Cc: Tony Luck <tony.luck@intel.com>
Cc:  <linux-hardening@vger.kernel.org>
Link: https://lore.kernel.org/r/20231205182622.1329923-3-keescook@chromium.org
Signed-off-by: Kees Cook <keescook@chromium.org>

Author: kees

fs/pstore/inode.c

@@ -35,6 +35,8 @@ static LIST_HEAD(records_list);
 static DEFINE_MUTEX(pstore_sb_lock);
 static struct super_block *pstore_sb;
 
+DEFINE_FREE(pstore_iput, struct inode *, if (_T) iput(_T))
+
 struct pstore_private {
 	struct list_head list;
 	struct dentry *dentry;
@@ -337,7 +339,7 @@ int pstore_put_backend_records(struct pstore_info *psi)
 int pstore_mkfile(struct dentry *root, struct pstore_record *record)
 {
 	struct dentry		*dentry;
-	struct inode		*inode;
+	struct inode		*inode __free(pstore_iput) = NULL;
 	int			rc = 0;
 	char			name[PSTORE_NAMELEN];
 	struct pstore_private	*private, *pos;
@@ -369,7 +371,7 @@ int pstore_mkfile(struct dentry *root, struct pstore_record *record)
 
 	private = kzalloc(sizeof(*private), GFP_KERNEL);
 	if (!private)
-		goto fail_inode;
+		return -ENOMEM;
 
 	dentry = d_alloc_name(root, name);
 	if (!dentry)
@@ -384,16 +386,14 @@ int pstore_mkfile(struct dentry *root, struct pstore_record *record)
 		inode_set_mtime_to_ts(inode,
 				      inode_set_ctime_to_ts(inode, record->time));
 
-	d_add(dentry, inode);
+	d_add(dentry, no_free_ptr(inode));
 
 	list_add(&private->list, &records_list);
 
 	return 0;
 
 fail_private:
 	free_pstore_private(private);
-fail_inode:
-	iput(inode);
 	return rc;
 }