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efi: Fix out-of-bounds read in variable_matches() 

The variable_matches() function can currently read "var_name[len]", for
example when:

 - var_name[0] == 'a',
 - len == 1
 - match_name points to the NUL-terminated string "ab".

This function is supposed to accept "var_name" inputs that are not
NUL-terminated (hence the "len" parameter"). Document the function, and
access "var_name[*match]" only if "*match" is smaller than "len".

Reported-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Cc: Peter Jones <pjones@redhat.com>
Cc: Matthew Garrett <mjg59@coreos.com>
Cc: Jason Andryuk <jandryuk@gmail.com>
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: <stable@vger.kernel.org> # v3.10+
Link: http://thread.gmane.org/gmane.comp.freedesktop.xorg.drivers.intel/86906
Signed-off-by: Matt Fleming <matt@codeblueprint.co.uk>
This commit is contained in:
Laszlo Ersek 2016-04-21 18:21:11 +02:00 committed by Matt Fleming
parent c3b46c7326
commit 630ba0cc7a
1 changed files with 26 additions and 11 deletions
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37
drivers/firmware/efi/vars.c
View File

@ -202,29 +202,44 @@ static const struct variable_validate variable_validate[] = {
{ NULL_GUID, "", NULL },
};
/*
* Check if @var_name matches the pattern given in @match_name.
*
* @var_name: an array of @len non-NUL characters.
* @match_name: a NUL-terminated pattern string, optionally ending in "*". A
* final "*" character matches any trailing characters @var_name,
* including the case when there are none left in @var_name.
* @match: on output, the number of non-wildcard characters in @match_name
* that @var_name matches, regardless of the return value.
* @return: whether @var_name fully matches @match_name.
*/
static bool
variable_matches(const char *var_name, size_t len, const char *match_name,
int *match)
{
for (*match = 0; ; (*match)++) {
char c = match_name[*match];
char u = var_name[*match];
/* Wildcard in the matching name means we've matched */
if (c == '*')
switch (c) {
case '*':
/* Wildcard in @match_name means we've matched. */
return true;
/* Case sensitive match */
if (!c && *match == len)
return true;
case '\0':
/* @match_name has ended. Has @var_name too? */
return (*match == len);
if (c != u)
default:
/*
* We've reached a non-wildcard char in @match_name.
* Continue only if there's an identical character in
* @var_name.
*/
if (*match < len && c == var_name[*match])
continue;
return false;
if (!c)
return true;
}
}
return true;
}
bool