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Commit 310ad754 authored by Jeremy Kerr's avatar Jeremy Kerr Committed by Matt Fleming
Browse files

efi: Clarify GUID length calculations 



At present, the handling of GUIDs in efivar file names isn't consistent.
We use GUID_LEN in some places, and 38 in others (GUID_LEN plus
separator), and implicitly use the presence of the trailing NUL.

This change removes the trailing NUL from GUID_LEN, so that we're
explicitly adding it when required. We also replace magic numbers
with GUID_LEN, and clarify the comments where appropriate.

We also fix the allocation size in efivar_create_sysfs_entry, where
we're allocating one byte too much, due to counting the trailing NUL
twice - once when calculating short_name_size, and once in the kzalloc.

Signed-off-by: default avatarJeremy Kerr <jeremy.kerr@canonical.com>
Signed-off-by: default avatarMatt Fleming <matt.fleming@intel.com>
parent f5f6a60a

drivers/firmware/efivars.c

+25 −8
Original line number Diff line number Diff line
@@ -95,7 +95,12 @@ MODULE_LICENSE("GPL"); 
MODULE_VERSION(EFIVARS_VERSION);



#define DUMP_NAME_LEN 52

#define GUID_LEN 37



/*

 * Length of a GUID string (strlen("aaaaaaaa-bbbb-cccc-dddd-eeeeeeeeeeee"))

 * not including trailing NUL

 */

#define GUID_LEN 36



/*

 * The maximum size of VariableName + Data = 1024
@@ -887,7 +892,11 @@ static int efivarfs_create(struct inode *dir, struct dentry *dentry, 
	struct efivar_entry *var;

	int namelen, i = 0, err = 0;



	if (dentry->d_name.len < 38)

	/*

	 * We need a GUID, plus at least one letter for the variable name,

	 * plus the '-' separator

	 */

	if (dentry->d_name.len < GUID_LEN + 2)

		return -EINVAL;



	inode = efivarfs_get_inode(dir->i_sb, dir, mode, 0);
@@ -900,7 +909,8 @@ static int efivarfs_create(struct inode *dir, struct dentry *dentry, 
		goto out;

	}



	namelen = dentry->d_name.len - GUID_LEN;

	/* length of the variable name itself: remove GUID and separator */

	namelen = dentry->d_name.len - GUID_LEN - 1;



	efivarfs_hex_to_guid(dentry->d_name.name + namelen + 1,

			&var->var.VendorGuid);
@@ -994,8 +1004,8 @@ int efivarfs_fill_super(struct super_block *sb, void *data, int silent) 


		len = utf16_strlen(entry->var.VariableName);



		/* GUID plus trailing NULL */

		name = kmalloc(len + 38, GFP_ATOMIC);

		/* name, plus '-', plus GUID, plus NUL*/

		name = kmalloc(len + 1 + GUID_LEN + 1, GFP_ATOMIC);

		if (!name)

			goto fail;
@@ -1006,7 +1016,7 @@ int efivarfs_fill_super(struct super_block *sb, void *data, int silent) 


		efi_guid_unparse(&entry->var.VendorGuid, name + len + 1);



		name[len+GUID_LEN] = '\0';

		name[len+GUID_LEN+1] = '\0';



		inode = efivarfs_get_inode(efivarfs_sb, root->d_inode,

					  S_IFREG | 0644, 0);
@@ -1435,11 +1445,18 @@ efivar_create_sysfs_entry(struct efivars *efivars, 
			  efi_char16_t *variable_name,

			  efi_guid_t *vendor_guid)

{

	int i, short_name_size = variable_name_size / sizeof(efi_char16_t) + 38;

	int i, short_name_size;

	char *short_name;

	struct efivar_entry *new_efivar;



	short_name = kzalloc(short_name_size + 1, GFP_KERNEL);

	/*

	 * Length of the variable bytes in ASCII, plus the '-' separator,

	 * plus the GUID, plus trailing NUL

	 */

	short_name_size = variable_name_size / sizeof(efi_char16_t)

				+ 1 + GUID_LEN + 1;



	short_name = kzalloc(short_name_size, GFP_KERNEL);

	new_efivar = kzalloc(sizeof(struct efivar_entry), GFP_KERNEL);



	if (!short_name || !new_efivar)  {