On 2023-08-01 08:59:17+0200, Willy Tarreau wrote:
> 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 ...
> }
As r == w is validated just below anyways we could move the assignment
buf[r] = '\0' after that check and then we don't need a new block.
> You'll also have to turn w to ssize_t then due to the test later BTW.
Will do in any case.
