2022-02-06 21:37:02

by Alexei Starovoitov

Subject: Re: [PATCH bpf-next v3 2/2] selftests/bpf: test maximum recursion depth for bpf_core_types_are_compat()

On Thu, Feb 3, 2022 at 4:55 PM Matteo Croce <[email protected]> wrote:
> --- a/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c
> +++ b/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c
> @@ -13,6 +13,11 @@
> #define CREATE_TRACE_POINTS
> #include "bpf_testmod-events.h"
>
> +typedef int (*func_proto_typedef___match)(long);
> +typedef int (*func_proto_typedef___overflow)(func_proto_typedef___match);

There is no need for "___flavor" on the kernel side of type definition.
It makes the test confusing to read.

> +func_proto_typedef___match funcp = NULL;
> +func_proto_typedef___overflow funcp_of = NULL;

We have BTF_TYPE_EMIT() macro to avoid unnecessary declaration.

> +typedef int (*func_proto_typedef___match)(long);
> +typedef int (*func_proto_typedef___overflow)(func_proto_typedef___match);

With <=1 in the previous patch such single depth of func_proto
was reaching the recursion limit.
Hence the fix <=0 was necessary.
I've also changed this test to:

+typedef int (*func_proto_typedef)(long);
+typedef int (*func_proto_typedef_nested1)(func_proto_typedef);
+typedef int (*func_proto_typedef_nested2)(func_proto_typedef_nested1);

in bpf_testmod.c and in progs/core_kern_overflow.c
and
bpf_core_type_exists(func_proto_typedef_nested2);
to go above the limit.

Also added bpf_core_type_exists(func_proto_typedef_nested1)
to progs/core_kern.c to stay at the limit.

Please see the result in bpf-next.

2022-02-07 10:30:05

by Matteo Croce

Subject: Re: [PATCH bpf-next v3 2/2] selftests/bpf: test maximum recursion depth for bpf_core_types_are_compat()

On Fri, Feb 4, 2022 at 8:38 PM Alexei Starovoitov
<[email protected]> wrote:
>
> On Thu, Feb 3, 2022 at 4:55 PM Matteo Croce <[email protected]> wrote:
> > --- a/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c
> > +++ b/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c
> > @@ -13,6 +13,11 @@
> > #define CREATE_TRACE_POINTS
> > #include "bpf_testmod-events.h"
> >
> > +typedef int (*func_proto_typedef___match)(long);
> > +typedef int (*func_proto_typedef___overflow)(func_proto_typedef___match);
>
> There is no need for "___flavor" on the kernel side of type definition.
> It makes the test confusing to read.
>
> > +func_proto_typedef___match funcp = NULL;
> > +func_proto_typedef___overflow funcp_of = NULL;
>
> We have BTF_TYPE_EMIT() macro to avoid unnecessary declaration.
>
> > +typedef int (*func_proto_typedef___match)(long);
> > +typedef int (*func_proto_typedef___overflow)(func_proto_typedef___match);
>
> With <=1 in the previous patch such single depth of func_proto
> was reaching the recursion limit.
> Hence the fix <=0 was necessary.
> I've also changed this test to:
>
> +typedef int (*func_proto_typedef)(long);
> +typedef int (*func_proto_typedef_nested1)(func_proto_typedef);
> +typedef int (*func_proto_typedef_nested2)(func_proto_typedef_nested1);
>
> in bpf_testmod.c and in progs/core_kern_overflow.c
> and
> bpf_core_type_exists(func_proto_typedef_nested2);
> to go above the limit.
>
> Also added bpf_core_type_exists(func_proto_typedef_nested1)
> to progs/core_kern.c to stay at the limit.
>
> Please see the result in bpf-next.

Awesome.
I've seen both patches in the repo, LGTM.

--
per aspera ad upstream