On Tue, Aug 01, 2023 at 07:30:16AM +0200, Thomas Weißschuh wrote:
> If read() fails and returns -1 buf would be accessed out of bounds.
>
> Signed-off-by: Thomas Weißschuh <linux@xxxxxxxxxxxxxx>
> ---
> tools/testing/selftests/nolibc/nolibc-test.c | 6 ++++++
> 1 file changed, 6 insertions(+)
>
> diff --git a/tools/testing/selftests/nolibc/nolibc-test.c b/tools/testing/selftests/nolibc/nolibc-test.c
> index 82714051c72f..a334f8450a34 100644
> --- a/tools/testing/selftests/nolibc/nolibc-test.c
> +++ b/tools/testing/selftests/nolibc/nolibc-test.c
> @@ -1031,6 +1031,12 @@ static int expect_vfprintf(int llen, int c, const char *expected, const char *fm
> lseek(fd, 0, SEEK_SET);
>
> r = read(fd, buf, sizeof(buf) - 1);
> + if (r == -1) {
> + llen += printf(" read() = %s", errorname(errno));
> + result(llen, FAIL);
> + return 1;
> + }
> +
> buf[r] = '\0';
In fact given the nature of this file (test if we properly implemented
our syscalls), I think that a more conservative approach is deserved
because if we messed up on read() we can have anything on return and we
don't want to trust that. As such I would suggest that we declare r as
ssize_t and verify that it's neither negative nor larger than
sizeof(buf)-1, which becomes:
if ((size_t)r >= sizeof(buf)) {
... fail ...
}
You'll also have to turn w to ssize_t then due to the test later BTW.
Willy
