Re: [PATCH] x86, mce: Fix stack out-of-bounds write in mce-inject.c:flags_read()

From: Borislav Petkov
Date: Fri Apr 27 2018 - 13:00:17 EST

On Fri, Apr 27, 2018 at 09:37:08AM -0700, Luck, Tony wrote:
> Each of the strings that we want to put into the buf[MAX_FLAG_OPT_SIZE]
> in flags_read() is two characters. But the sprintf() adds a trailing newline
> and will add a terminating NUL byte. So MAX_FLAG_OPT_SIZE needs to be 4.

... and I dumped the n here:

n = sprintf(buf, "%s\n", flags_options[inj_type])

and it was 3 but 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."

So I'll extend the commit message with that and apply it.



Good mailing practices for 400: avoid top-posting and trim the reply.