Re: [PATCH bpf-next v3 2/4] bpf: Verifier support for sleepable raw tracepoint programs

[Puranjay Mohan <puranjay@kernel.org>]

Mykyta Yatsenko <mykyta.yatsenko5@gmail.com> writes:

> From: Mykyta Yatsenko <yatsenko@meta.com>
>
> Add BPF_TRACE_RAW_TP to the set of tracing program attach types
> that can be loaded as sleepable in can_be_sleepable().
>
> Reject sleepable programs that target non-faultable tracepoints
> at load time in bpf_check_attach_target(), providing a clear
> verifier error message.
>
> Signed-off-by: Mykyta Yatsenko <yatsenko@meta.com>

Acked-by: Puranjay Mohan <puranjay@kernel.org>

> ---
>  kernel/bpf/verifier.c | 9 ++++++++-
>  1 file changed, 8 insertions(+), 1 deletion(-)
>
> diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
> index 8e4f69918693..95b33b85698f 100644
> --- a/kernel/bpf/verifier.c
> +++ b/kernel/bpf/verifier.c
> @@ -25216,6 +25216,12 @@ int bpf_check_attach_target(struct bpf_verifier_log *log,
>  		btp = bpf_get_raw_tracepoint(tname);
>  		if (!btp)
>  			return -EINVAL;
> +		if (prog->sleepable && !tracepoint_is_faultable(btp->tp)) {
> +			bpf_log(log, "Sleepable program cannot attach to non-faultable tracepoint %s\n",
> +				tname);
> +			bpf_put_raw_tracepoint(btp);
> +			return -EINVAL;
> +		}
>  		fname = kallsyms_lookup((unsigned long)btp->bpf_func, NULL, NULL, NULL,
>  					trace_symbol);
>  		bpf_put_raw_tracepoint(btp);
> @@ -25432,6 +25438,7 @@ static bool can_be_sleepable(struct bpf_prog *prog)
>  		case BPF_MODIFY_RETURN:
>  		case BPF_TRACE_ITER:
>  		case BPF_TRACE_FSESSION:
> +		case BPF_TRACE_RAW_TP:
>  			return true;
>  		default:
>  			return false;
> @@ -25461,7 +25468,7 @@ static int check_attach_btf_id(struct bpf_verifier_env *env)
>  	}
>  
>  	if (prog->sleepable && !can_be_sleepable(prog)) {
> -		verbose(env, "Only fentry/fexit/fmod_ret, lsm, iter, uprobe, and struct_ops programs can be sleepable\n");
> +		verbose(env, "Only fentry/fexit/fmod_ret, lsm, iter, uprobe, struct_ops, and raw_tp programs can be sleepable\n");
>  		return -EINVAL;
>  	}
>  
>
> -- 
> 2.52.0