From 630ba0cc7a6dbafbdee43795617c872b35cde1b4 Mon Sep 17 00:00:00 2001 From: Laszlo Ersek Date: Thu, 21 Apr 2016 18:21:11 +0200 Subject: [PATCH] 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 Signed-off-by: Laszlo Ersek Cc: Peter Jones Cc: Matthew Garrett Cc: Jason Andryuk Cc: Jani Nikula Cc: # v3.10+ Link: http://thread.gmane.org/gmane.comp.freedesktop.xorg.drivers.intel/86906 Signed-off-by: Matt Fleming --- drivers/firmware/efi/vars.c | 37 ++++++++++++++++++++++++++----------- 1 file 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 -- 2.20.1