Re: [PATCH bpf-next] bpftool: Add debug mode for gen_loader.

[Alexei Starovoitov <ast@fb.com>]

On 12/5/21 11:42 AM, Andrii Nakryiko wrote:
>>
>> diff --git a/tools/bpf/bpftool/prog.c b/tools/bpf/bpftool/prog.c
>> index e47e8b06cc3d..b9f42e9e9067 100644
>> --- a/tools/bpf/bpftool/prog.c
>> +++ b/tools/bpf/bpftool/prog.c
>> @@ -1779,12 +1779,14 @@ static int try_loader(struct gen_loader_opts *gen)
>>          ctx = alloca(ctx_sz);
>>          memset(ctx, 0, ctx_sz);
>>          ctx->sz = ctx_sz;
>> -       ctx->log_level = 1;
>> -       ctx->log_size = log_buf_sz;
>> -       log_buf = malloc(log_buf_sz);
>> -       if (!log_buf)
>> -               return -ENOMEM;
>> -       ctx->log_buf = (long) log_buf;
>> +       if (verifier_logs) {
>> +               ctx->log_level = 1 + 2 + 4;
>> +               ctx->log_size = log_buf_sz;
>> +               log_buf = malloc(log_buf_sz);
> 
> if verifier_logs is false, log_buf will now be left uninitialized and
> passed like that into free(log_buf), crashing or corrupting memory.
> I've fixed it up by NULL initializaing and pushed to bpf-next.

Indeed. Weird that compiler didn't complain and bpftool didn't crash.
Thanks!