From 4adc7d7ee640b0dcfffa0ee6d2aa24c1ffd74ff4 Mon Sep 17 00:00:00 2001 From: Masahiro Yamada Date: Tue, 24 May 2022 01:46:22 +0900 Subject: [PATCH] modpost: fix undefined behavior of is_arm_mapping_symbol() [ Upstream commit d6b732666a1bae0df3c3ae06925043bba34502b1 ] The return value of is_arm_mapping_symbol() is unpredictable when "$" is passed in. strchr(3) says: The strchr() and strrchr() functions return a pointer to the matched character or NULL if the character is not found. The terminating null byte is considered part of the string, so that if c is specified as '\0', these functions return a pointer to the terminator. When str[1] is '\0', strchr("axtd", str[1]) is not NULL, and str[2] is referenced (i.e. buffer overrun). Test code --------- char str1[] = "abc"; char str2[] = "ab"; strcpy(str1, "$"); strcpy(str2, "$"); printf("test1: %d\n", is_arm_mapping_symbol(str1)); printf("test2: %d\n", is_arm_mapping_symbol(str2)); Result ------ test1: 0 test2: 1 Signed-off-by: Masahiro Yamada Reviewed-by: Nick Desaulniers Signed-off-by: Sasha Levin --- scripts/mod/modpost.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c index 7a5bddb8913e9..94041ee32798f 100644 --- a/scripts/mod/modpost.c +++ b/scripts/mod/modpost.c @@ -1260,7 +1260,8 @@ static int secref_whitelist(const struct sectioncheck *mismatch, static inline int is_arm_mapping_symbol(const char *str) { - return str[0] == '$' && strchr("axtd", str[1]) + return str[0] == '$' && + (str[1] == 'a' || str[1] == 'd' || str[1] == 't' || str[1] == 'x') && (str[2] == '\0' || str[2] == '.'); }