ext4: fold quota accounting into ext4_xattr_inode_lookup_create()

JIRA: https://issues.redhat.com/browse/RHEL-48282
Tested: With xfstests
CVE: CVE-2024-40972

When allocating EA inode, quota accounting is done just before
ext4_xattr_inode_lookup_create(). Logically these two operations belong
together so just fold quota accounting into
ext4_xattr_inode_lookup_create(). We also make
ext4_xattr_inode_lookup_create() return the looked up / created inode to
convert the function to a more standard calling convention.

Signed-off-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20240209112107.10585-1-jack@suse.cz
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
(cherry picked from commit 8208c41)
Signed-off-by: Carlos Maiolino <cmaiolino@redhat.com>

Author: cmaiolino

fs/ext4/xattr.c

@@ -1566,46 +1566,49 @@ ext4_xattr_inode_cache_find(struct inode *inode, const void *value,
 /*
  * Add value of the EA in an inode.
  */
-static int ext4_xattr_inode_lookup_create(handle_t *handle, struct inode *inode,
-					  const void *value, size_t value_len,
-					  struct inode **ret_inode)
+static struct inode *ext4_xattr_inode_lookup_create(handle_t *handle,
+		struct inode *inode, const void *value, size_t value_len)
 {
 	struct inode *ea_inode;
 	u32 hash;
 	int err;
 
+	/* Account inode & space to quota even if sharing... */
+	err = ext4_xattr_inode_alloc_quota(inode, value_len);
+	if (err)
+		return ERR_PTR(err);
+
 	hash = ext4_xattr_inode_hash(EXT4_SB(inode->i_sb), value, value_len);
 	ea_inode = ext4_xattr_inode_cache_find(inode, value, value_len, hash);
 	if (ea_inode) {
 		err = ext4_xattr_inode_inc_ref(handle, ea_inode);
-		if (err) {
-			iput(ea_inode);
-			return err;
-		}
-
-		*ret_inode = ea_inode;
-		return 0;
+		if (err)
+			goto out_err;
+		return ea_inode;
 	}
 
 	/* Create an inode for the EA value */
 	ea_inode = ext4_xattr_inode_create(handle, inode, hash);
-	if (IS_ERR(ea_inode))
-		return PTR_ERR(ea_inode);
+	if (IS_ERR(ea_inode)) {
+		ext4_xattr_inode_free_quota(inode, NULL, value_len);
+		return ea_inode;
+	}
 
 	err = ext4_xattr_inode_write(handle, ea_inode, value, value_len);
 	if (err) {
 		if (ext4_xattr_inode_dec_ref(handle, ea_inode))
 			ext4_warning_inode(ea_inode, "cleanup dec ref error %d", err);
-		iput(ea_inode);
-		return err;
+		goto out_err;
 	}
 
 	if (EA_INODE_CACHE(inode))
 		mb_cache_entry_create(EA_INODE_CACHE(inode), GFP_NOFS, hash,
 				      ea_inode->i_ino, true /* reusable */);
-
-	*ret_inode = ea_inode;
-	return 0;
+	return ea_inode;
+out_err:
+	iput(ea_inode);
+	ext4_xattr_inode_free_quota(inode, NULL, value_len);
+	return ERR_PTR(err);
 }
 
 /*
@@ -1713,16 +1716,11 @@ static int ext4_xattr_set_entry(struct ext4_xattr_info *i,
 	if (i->value && in_inode) {
 		WARN_ON_ONCE(!i->value_len);
 
-		ret = ext4_xattr_inode_alloc_quota(inode, i->value_len);
-		if (ret)
-			goto out;
-
-		ret = ext4_xattr_inode_lookup_create(handle, inode, i->value,
-						     i->value_len,
-						     &new_ea_inode);
-		if (ret) {
+		new_ea_inode = ext4_xattr_inode_lookup_create(handle, inode,
+					i->value, i->value_len);
+		if (IS_ERR(new_ea_inode)) {
+			ret = PTR_ERR(new_ea_inode);
 			new_ea_inode = NULL;
-			ext4_xattr_inode_free_quota(inode, NULL, i->value_len);
 			goto out;
 		}
 	}