Re: [f2fs-dev] [PATCH v7 2/8] fs: Add standard casefolding support

From: Al Viro <viro@zeniv.linux.org.uk>
To: Daniel Rosenberg <drosen@google.com>
Cc: kernel-team@android.com, Theodore Ts'o <tytso@mit.edu>,
	Jonathan Corbet <corbet@lwn.net>,
	Richard Weinberger <richard@nod.at>,
	Andreas Dilger <adilger.kernel@dilger.ca>,
	linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org,
	linux-f2fs-devel@lists.sourceforge.net,
	Eric Biggers <ebiggers@kernel.org>,
	linux-fscrypt@vger.kernel.org, linux-mtd@lists.infradead.org,
	linux-fsdevel@vger.kernel.org, Jaegeuk Kim <jaegeuk@kernel.org>,
	linux-ext4@vger.kernel.org,
	Gabriel Krisman Bertazi <krisman@collabora.com>
Subject: Re: [f2fs-dev] [PATCH v7 2/8] fs: Add standard casefolding support
Date: Sat, 8 Feb 2020 02:12:16 +0000
Message-ID: <20200208021216.GE23230@ZenIV.linux.org.uk> (raw)
In-Reply-To: <20200208013552.241832-3-drosen@google.com>

On Fri, Feb 07, 2020 at 05:35:46PM -0800, Daniel Rosenberg wrote:

> +int generic_ci_d_compare(const struct dentry *dentry, unsigned int len,
> +			  const char *str, const struct qstr *name)
> +{
> +	const struct dentry *parent = READ_ONCE(dentry->d_parent);
> +	const struct inode *inode = READ_ONCE(parent->d_inode);
> +	const struct super_block *sb = dentry->d_sb;
> +	const struct unicode_map *um = sb->s_encoding;
> +	struct qstr entry = QSTR_INIT(str, len);
> +	int ret;
> +
> +	if (!inode || !needs_casefold(inode))
> +		goto fallback;
> +
> +	ret = utf8_strncasecmp(um, name, &entry);

Again, is that safe in case when the contents of the string str points to
keeps changing under you?

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