Re: [PATCH 3/6] efivarfs: make variable_is_present use dcache lookup

[Al Viro <viro@zeniv.linux.org.uk>]

On Tue, Dec 10, 2024 at 12:02:21PM -0500, James Bottomley wrote:
> Instead of searching the variable entry list for a variable, use the
> dcache lookup functions to find it instead.  Also add an efivarfs_
> prefix to the function now it is no longer static.

> +bool efivarfs_variable_is_present(efi_char16_t *variable_name,
> +				  efi_guid_t *vendor, void *data)
> +{
> +	char *name = efivar_get_utf8name(variable_name, vendor);
> +	struct super_block *sb = data;
> +	struct dentry *dentry;
> +	struct qstr qstr;
> +
> +	if (!name)
> +		return true;
> +
> +	qstr.name = name;
> +	qstr.len = strlen(name);
> +	dentry = d_hash_and_lookup(sb->s_root, &qstr);
> +	kfree(name);
> +	if (dentry)
> +		dput(dentry);

If that ever gets called with efivarfs_valid_name(name, strlen(name))
being false, that's going to oops...