From e0b510a4170e220d978a6cfbe25e634193fffbfa Mon Sep 17 00:00:00 2001 From: Tony Luck Date: Fri, 27 Apr 2018 09:37:08 -0700 Subject: [PATCH] x86/MCE: Fix stack out-of-bounds write in mce-inject.c: Flags_read() commit 985c78d3ff8e9c74450fa2bb08eb55e680d999ca upstream. Each of the strings that we want to put into the buf[MAX_FLAG_OPT_SIZE] in flags_read() is two characters long. But the sprintf() adds a trailing newline and will add a terminating NUL byte. So MAX_FLAG_OPT_SIZE needs to be 4. sprintf() calls vsnprintf() and *that* does return: " * The return value is the number of characters which would * be generated for the given input, excluding the trailing * '\0', as per ISO C99." Note the "excluding". Reported-by: Dmitry Vyukov Signed-off-by: Tony Luck Signed-off-by: Borislav Petkov Signed-off-by: Thomas Gleixner Cc: stable@vger.kernel.org Cc: linux-edac Link: http://lkml.kernel.org/r/20180427163707.ktaiysvbk3yhk4wm@agluck-desk Signed-off-by: Greg Kroah-Hartman --- arch/x86/kernel/cpu/mcheck/mce-inject.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/x86/kernel/cpu/mcheck/mce-inject.c b/arch/x86/kernel/cpu/mcheck/mce-inject.c index 231ad23b24a9..8fec687b3e44 100644 --- a/arch/x86/kernel/cpu/mcheck/mce-inject.c +++ b/arch/x86/kernel/cpu/mcheck/mce-inject.c @@ -48,7 +48,7 @@ static struct dentry *dfs_inj; static u8 n_banks; -#define MAX_FLAG_OPT_SIZE 3 +#define MAX_FLAG_OPT_SIZE 4 #define NBCFG 0x44 enum injection_type { -- 2.20.1