Re: [PATCH] tests/tcg: fix buffer overflow in multiarch/linux/linux-sigrtminmax

[Markus Armbruster <armbru@redhat.com>]

Max Filippov <jcmvbkbc@gmail.com> writes:

> Fix new_argv allocation size to be `(argc + 2) * sizeof(char *)` bytes,
> which matches the way it's used to store `argc + 2` pointers.
>
> This fixes the test for me, which otherwise fails on xtensa with the
> following message
>
>   linux-sigrtminmax.c: 59: main: Assertion `execve(new_argv[0], new_argv, environ) == 0' failed.'.
>
> Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
> ---
>  tests/tcg/multiarch/linux/linux-sigrtminmax.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/tests/tcg/multiarch/linux/linux-sigrtminmax.c b/tests/tcg/multiarch/linux/linux-sigrtminmax.c
> index a7059aacd9cb..b5ea65f3d393 100644
> --- a/tests/tcg/multiarch/linux/linux-sigrtminmax.c
> +++ b/tests/tcg/multiarch/linux/linux-sigrtminmax.c
> @@ -39,7 +39,7 @@ int main(int argc, char **argv)
>      assert(qemu);
>  
>      if (!getenv("QEMU_RTSIG_MAP")) {
> -        char **new_argv = malloc((argc + 2) + sizeof(char *));
> +        char **new_argv = malloc((argc + 2) * sizeof(char *));

If you can switch to glib's malloc, then g_new(argc + 2, sizeof(char *))
is better.  Yes, @argc can't become big enough for the multiplication to
overflow, but g_new() removes the need for reasoning.

>          int tsig1, hsig1, count1, tsig2, hsig2, count2;
>          char rt_sigmap[64];