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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: Jeremy Kerr <jeremy.kerr@canonical.com>
Signed-off-by: Matt Fleming <matt.fleming@intel.com>
This commit is contained in:
Jeremy Kerr 2012-10-19 15:16:45 +08:00 committed by Matt Fleming
parent f5f6a60ad5
commit 310ad75448
1 changed files with 25 additions and 8 deletions
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33
drivers/firmware/efivars.c
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@ -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) {