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Commit da27a243 authored by Matt Fleming's avatar Matt Fleming
Browse files

efivarfs: guid part of filenames are case-insensitive 



It makes no sense to treat the following filenames as unique,

	VarName-abcdefab-abcd-abcd-abcd-abcdefabcdef
	VarName-ABCDEFAB-ABCD-ABCD-ABCD-ABCDEFABCDEF
	VarName-ABcDEfAB-ABcD-ABcD-ABcD-ABcDEfABcDEf
	VarName-aBcDEfAB-aBcD-aBcD-aBcD-aBcDEfaBcDEf
	... etc ...

since the guid will be converted into a binary representation, which
has no case.

Roll our own dentry operations so that we can treat the variable name
part of filenames ("VarName" in the above example) as case-sensitive,
but the guid portion as case-insensitive. That way, efivarfs will
refuse to create the above files if any one already exists.

Reported-by: default avatarLingzhu Xiang <lxiang@redhat.com>
Cc: Matthew Garrett <mjg59@srcf.ucam.org>
Cc: Jeremy Kerr <jeremy.kerr@canonical.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: default avatarMatt Fleming <matt.fleming@intel.com>
parent 47f531e8

drivers/firmware/efivars.c

+93 −2
Original line number Diff line number Diff line
@@ -1043,6 +1043,84 @@ static int efivarfs_unlink(struct inode *dir, struct dentry *dentry) 
	return -EINVAL;

};



/*

 * Compare two efivarfs file names.

 *

 * An efivarfs filename is composed of two parts,

 *

 *	1. A case-sensitive variable name

 *	2. A case-insensitive GUID

 *

 * So we need to perform a case-sensitive match on part 1 and a

 * case-insensitive match on part 2.

 */

static int efivarfs_d_compare(const struct dentry *parent, const struct inode *pinode,

			      const struct dentry *dentry, const struct inode *inode,

			      unsigned int len, const char *str,

			      const struct qstr *name)

{

	int guid = len - GUID_LEN;



	if (name->len != len)

		return 1;



	/* Case-sensitive compare for the variable name */

	if (memcmp(str, name->name, guid))

		return 1;



	/* Case-insensitive compare for the GUID */

	return strncasecmp(name->name + guid, str + guid, GUID_LEN);

}



static int efivarfs_d_hash(const struct dentry *dentry,

			   const struct inode *inode, struct qstr *qstr)

{

	unsigned long hash = init_name_hash();

	const unsigned char *s = qstr->name;

	unsigned int len = qstr->len;



	if (!efivarfs_valid_name(s, len))

		return -EINVAL;



	while (len-- > GUID_LEN)

		hash = partial_name_hash(*s++, hash);



	/* GUID is case-insensitive. */

	while (len--)

		hash = partial_name_hash(tolower(*s++), hash);



	qstr->hash = end_name_hash(hash);

	return 0;

}



/*

 * Retaining negative dentries for an in-memory filesystem just wastes

 * memory and lookup time: arrange for them to be deleted immediately.

 */

static int efivarfs_delete_dentry(const struct dentry *dentry)

{

	return 1;

}



static struct dentry_operations efivarfs_d_ops = {

	.d_compare = efivarfs_d_compare,

	.d_hash = efivarfs_d_hash,

	.d_delete = efivarfs_delete_dentry,

};



static struct dentry *efivarfs_alloc_dentry(struct dentry *parent, char *name)

{

	struct qstr q;



	q.name = name;

	q.len = strlen(name);



	if (efivarfs_d_hash(NULL, NULL, &q))

		return NULL;



	return d_alloc(parent, &q);

}



static int efivarfs_fill_super(struct super_block *sb, void *data, int silent)

{

	struct inode *inode = NULL;
@@ -1058,6 +1136,7 @@ static int efivarfs_fill_super(struct super_block *sb, void *data, int silent) 
	sb->s_blocksize_bits    = PAGE_CACHE_SHIFT;

	sb->s_magic             = EFIVARFS_MAGIC;

	sb->s_op                = &efivarfs_ops;

	sb->s_d_op		= &efivarfs_d_ops;

	sb->s_time_gran         = 1;



	inode = efivarfs_get_inode(sb, NULL, S_IFDIR | 0755, 0);
@@ -1098,7 +1177,7 @@ static int efivarfs_fill_super(struct super_block *sb, void *data, int silent) 
		if (!inode)

			goto fail_name;



		dentry = d_alloc_name(root, name);

		dentry = efivarfs_alloc_dentry(root, name);

		if (!dentry)

			goto fail_inode;
@@ -1148,8 +1227,20 @@ static struct file_system_type efivarfs_type = { 
	.kill_sb = efivarfs_kill_sb,

};



/*

 * Handle negative dentry.

 */

static struct dentry *efivarfs_lookup(struct inode *dir, struct dentry *dentry,

				      unsigned int flags)

{

	if (dentry->d_name.len > NAME_MAX)

		return ERR_PTR(-ENAMETOOLONG);

	d_add(dentry, NULL);

	return NULL;

}



static const struct inode_operations efivarfs_dir_inode_operations = {

	.lookup = simple_lookup,

	.lookup = efivarfs_lookup,

	.unlink = efivarfs_unlink,

	.create = efivarfs_create,

};