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;
+
+ /* Find part 1, the variable name. */
+ guid = q - (const char *)name->name;
+
+ /* 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)
+{
+ const unsigned char *us;
+ char lower[NAME_MAX];
+ int guid;
+
+ if (!efivarfs_valid_name(qstr->name, qstr->len))
+ return -EINVAL;
+
+ if (qstr->len > NAME_MAX)
+ return -ENAMETOOLONG;
+
+ us = strchr(qstr->name, '-');
+ if (!us)
+ return -EINVAL;
+
+ /* The variable name part is case-sensitive */
+ guid = us - qstr->name;
+ memcpy(lower, qstr->name, guid);
+
+ /* GUID is case-insensitive. */
+ for (us = &qstr->name[guid]; guid < qstr->len; guid++)
+ lower[guid] = tolower(*us++);
+ lower[guid] = '\0';
+
+ qstr->hash = full_name_hash(lower, qstr->len);
+ 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 int efivarfs_fill_super(struct super_block *sb, void *data, int silent)
{
struct inode *inode = NULL;
@@ -1064,6 +1150,7 @@ 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);
@@ -1154,8 +1241,20 @@ 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,
};
--
1.7.11.7
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