Commit 4c43ab1b authored by Al Viro's avatar Al Viro
Browse files

generic_ci_d_compare(): use shortname_storage 



... and check the "name might be unstable" predicate
the right way.

Reviewed-by: default avatarJeff Layton <jlayton@kernel.org>
Reviewed-by: default avatarGabriel Krisman Bertazi <gabriel@krisman.be>
Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
parent 7e327016

fs/libfs.c

+8 −7
Original line number Diff line number Diff line
@@ -1789,7 +1789,7 @@ int generic_ci_d_compare(const struct dentry *dentry, unsigned int len, 
{

	const struct dentry *parent;

	const struct inode *dir;

	char strbuf[DNAME_INLINE_LEN];

	union shortname_store strbuf;

	struct qstr qstr;



	/*
@@ -1809,22 +1809,23 @@ int generic_ci_d_compare(const struct dentry *dentry, unsigned int len, 
	if (!dir || !IS_CASEFOLDED(dir))

		return 1;



	qstr.len = len;

	qstr.name = str;

	/*

	 * If the dentry name is stored in-line, then it may be concurrently

	 * modified by a rename.  If this happens, the VFS will eventually retry

	 * the lookup, so it doesn't matter what ->d_compare() returns.

	 * However, it's unsafe to call utf8_strncasecmp() with an unstable

	 * string.  Therefore, we have to copy the name into a temporary buffer.

	 * As above, len is guaranteed to match str, so the shortname case

	 * is exactly when str points to ->d_shortname.

	 */

	if (len <= DNAME_INLINE_LEN - 1) {

		memcpy(strbuf, str, len);

		strbuf[len] = 0;

		str = strbuf;

	if (qstr.name == dentry->d_shortname.string) {

		strbuf = dentry->d_shortname; // NUL is guaranteed to be in there

		qstr.name = strbuf.string;

		/* prevent compiler from optimizing out the temporary buffer */

		barrier();

	}

	qstr.len = len;

	qstr.name = str;



	return utf8_strncasecmp(dentry->d_sb->s_encoding, name, &qstr);

}