netdev - Re: [PATCH bpf-next v2 02/14] selftests/bpf: Test referenced kptr arguments of struct

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Message-ID: <16c2f9b5d9c91bf5b8ee8c18a17c9cf846b394e8.camel@gmail.com>
Date: Thu, 23 Jan 2025 01:57:24 -0800
From: Eduard Zingerman <eddyz87@...il.com>
To: Amery Hung <ameryhung@...il.com>, netdev@...r.kernel.org
Cc: bpf@...r.kernel.org, daniel@...earbox.net, andrii@...nel.org, 
	alexei.starovoitov@...il.com, martin.lau@...nel.org, sinquersw@...il.com, 
	toke@...hat.com, jhs@...atatu.com, jiri@...nulli.us, stfomichev@...il.com, 
	ekarani.silvestre@....ufcg.edu.br, yangpeihao@...u.edu.cn, 
	xiyou.wangcong@...il.com, yepeilin.cs@...il.com, amery.hung@...edance.com
Subject: Re: [PATCH bpf-next v2 02/14] selftests/bpf: Test referenced kptr
 arguments of struct_ops programs

On Fri, 2024-12-20 at 11:55 -0800, Amery Hung wrote:

Reviewed-by: Eduard Zingerman <eddyz87@...il.com>

[...]

> diff --git a/tools/testing/selftests/bpf/progs/struct_ops_refcounted_fail__global_subprog.c b/tools/testing/selftests/bpf/progs/struct_ops_refcounted_fail__global_subprog.c
> new file mode 100644
> index 000000000000..43493a7ead39
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/progs/struct_ops_refcounted_fail__global_subprog.c
> @@ -0,0 +1,37 @@
> +#include <vmlinux.h>
> +#include <bpf/bpf_tracing.h>
> +#include "../test_kmods/bpf_testmod.h"
> +#include "bpf_misc.h"
> +
> +char _license[] SEC("license") = "GPL";
> +
> +extern void bpf_task_release(struct task_struct *p) __ksym;
> +
> +__noinline int subprog_release(__u64 *ctx __arg_ctx)
> +{
> +	struct task_struct *task = (struct task_struct *)ctx[1];
> +	int dummy = (int)ctx[0];
> +
> +	bpf_task_release(task);
> +
> +	return dummy + 1;
> +}
> +
> +/* Test that the verifier rejects a program that contains a global
> + * subprogram with referenced kptr arguments
> + */
> +SEC("struct_ops/test_refcounted")

Nit: I'd add a __msg("Validating subprog_release() func#1...")
     before the error message match, just to make sure that
     error is reported when subprog_release() is verified.

> +__failure __msg("invalid bpf_context access off=8. Reference may already be released")
> +int refcounted_fail__global_subprog(unsigned long long *ctx)
> +{
> +	struct task_struct *task = (struct task_struct *)ctx[1];
> +
> +	bpf_task_release(task);
> +
> +	return subprog_release(ctx);
> +}
> +
> +SEC(".struct_ops.link")
> +struct bpf_testmod_ops testmod_ref_acquire = {
> +	.test_refcounted = (void *)refcounted_fail__global_subprog,
> +};

[...]