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authorLaszlo Ersek <lersek@redhat.com>2016-04-21 18:21:11 +0200
committerMatt Fleming <matt@codeblueprint.co.uk>2016-04-22 19:41:41 +0100
commit630ba0cc7a6dbafbdee43795617c872b35cde1b4 (patch)
tree0dbc30e47cd62af70ac76630074d4a0d9c8581ff /drivers/firmware
parentc3b46c73264b03000d1e18b22f5caf63332547c9 (diff)
downloadlinux-630ba0cc7a6dbafbdee43795617c872b35cde1b4.tar.bz2
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>
Diffstat (limited to 'drivers/firmware')
-rw-r--r--drivers/firmware/efi/vars.c37
1 files changed, 26 insertions, 11 deletions
diff --git a/drivers/firmware/efi/vars.c b/drivers/firmware/efi/vars.c
index 0ac594c0a234..34b741940494 100644
--- a/drivers/firmware/efi/vars.c
+++ b/drivers/firmware/efi/vars.c
@@ -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