Re: [PATCH bpf-next v3 2/2] bpf: Warn on non-preallocated case for missed trace types

[Yonghong Song <yhs@fb.com>]

On 7/9/22 8:44 AM, Yafang Shao wrote:
> The raw tracepoint may cause unexpected memory allocation if we set
> BPF_F_NO_PREALLOC. So let's warn on it.

Please extend raw_tracepoint to other attach types which
may cause runtime map allocations.

> 
> Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
> ---
>   kernel/bpf/verifier.c | 18 +++++++++++++-----
>   1 file changed, 13 insertions(+), 5 deletions(-)
> 
> diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
> index e3cf6194c24f..3cd8260827e0 100644
> --- a/kernel/bpf/verifier.c
> +++ b/kernel/bpf/verifier.c
> @@ -12574,14 +12574,20 @@ static int check_map_prealloc(struct bpf_map *map)
>   		!(map->map_flags & BPF_F_NO_PREALLOC);
>   }
>   
> -static bool is_tracing_prog_type(enum bpf_prog_type type)
> +static bool is_tracing_prog_type(enum bpf_prog_type prog_type,
> +				 enum bpf_attach_type attach_type)
>   {
> -	switch (type) {
> +	switch (prog_type) {
>   	case BPF_PROG_TYPE_KPROBE:
>   	case BPF_PROG_TYPE_TRACEPOINT:
>   	case BPF_PROG_TYPE_PERF_EVENT:
>   	case BPF_PROG_TYPE_RAW_TRACEPOINT:
> +	case BPF_PROG_TYPE_RAW_TRACEPOINT_WRITABLE:
>   		return true;
> +	case BPF_PROG_TYPE_TRACING:
> +		if (attach_type == BPF_TRACE_RAW_TP)
> +			return true;

As Alexei mentioned earlier, here we should have
		if (attach_type != BPF_TRACE_ITER)
			return true;

For attach types with BPF_PROG_TYPE_TRACING programs,
BPF_TRACE_ITER attach type can only appear in process context.
All other attach types may appear in non-process context.

> +		return false;
>   	default:
>   		return false;
>   	}
> @@ -12601,7 +12607,9 @@ static int check_map_prog_compatibility(struct bpf_verifier_env *env,
>   					struct bpf_prog *prog)
>   
>   {
> +	enum bpf_attach_type attach_type = prog->expected_attach_type;
>   	enum bpf_prog_type prog_type = resolve_prog_type(prog);
> +
[...]