On Mon, Feb 11, 2013 at 02:28:55PM +0000, Matt Fleming wrote:
> From: Matt Fleming <[email protected]>
>
> 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: Lingzhu Xiang <[email protected]>
> Cc: Matthew Garrett <[email protected]>
> Cc: Jeremy Kerr <[email protected]>
> Cc: Al Viro <[email protected]>
> Signed-off-by: Matt Fleming <[email protected]>
> ---
> drivers/firmware/efivars.c | 101
> ++++++++++++++++++++++++++++++++++++++++++++-
> 1 file changed, 100 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/firmware/efivars.c b/drivers/firmware/efivars.c
> index a4fa409..10088fd 100644
> --- a/drivers/firmware/efivars.c
> +++ b/drivers/firmware/efivars.c
> @@ -79,6 +79,7 @@
> #include <linux/device.h>
> #include <linux/slab.h>
> #include <linux/pstore.h>
> +#include <linux/ctype.h>
>
> #include <linux/fs.h>
> #include <linux/ramfs.h>
> @@ -1049,6 +1050,91 @@ 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)
> +{
> + const char *q;
> + int guid;
> +
> + /*
> + * If the string we're being asked to compare doesn't match
> + * the expected format return "no match".
> + */
> + if (!efivarfs_valid_name(str, len))
> + return 1;
> + if (!(q = strchr(name->name, '-')))
> + return 1;
No. Why check that again, when we'd already called ->d_hash() on the
incoming name *and* candidate dentry? And buggered off on any potential
errors.
> +
> + /* Find part 1, the variable name. */
> + guid = q - (const char *)name->name;
No need to do strchr() for that - you know that name passes
efivarfs_valid_name(), so you know how far from the end will GUID part begin.
> + /* Case-sensitive compare for the variable name */
> + if (memcmp(str, name->name, guid))
> + return 1;
> +
> + /* Case-insensitive compare for the GUID */
> + return strcasecmp(&name->name[guid], &str[guid]);
> +}
> +static int efivarfs_d_hash(const struct dentry *dentry,
> + const struct inode *inode, struct qstr *qstr)
> +{
Egads, man...
[snip the horror with copying the name]
unsigned long hash = init_name_hash();
const unsigned char *s = qstr->name;
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);
return end_name_hash(hash);
--
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