From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-13.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id B88D9C433B4 for ; Wed, 14 Apr 2021 18:02:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 90C4A61177 for ; Wed, 14 Apr 2021 18:02:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1351760AbhDNSCv (ORCPT ); Wed, 14 Apr 2021 14:02:51 -0400 Received: from mail-ua1-f45.google.com ([209.85.222.45]:46611 "EHLO mail-ua1-f45.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1351678AbhDNSCt (ORCPT ); Wed, 14 Apr 2021 14:02:49 -0400 Received: by mail-ua1-f45.google.com with SMTP id v23so6658637uaq.13; Wed, 14 Apr 2021 11:02:27 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=NFAyc/0OnDwFm+c9BzGYO5+jcNQjjTnGY0d4m8lX60E=; b=Z3Z1LxlxODt8jVq/0tbLAAdWm3M0vh2hsD56eUL1CMRjfFGWnYNq3bzX0d1xAff13F oI8ttpbe77BcwYNZMTqhIqQl7OoKblbzcZhtg9gwd4Wq4RSeM4XSIY8bCcnrRUjzmV9/ 17/q2rgPMCJEhQgyAdzZlw08rNr2O0aUfGhL40/BQzVzm8xtObG4tqpDNgna8gHisK8d ffAwT8ID2IdqF8vO3Zdx9N/lDAaU4UoB7KDXAtcW0344D4DHtMoQTGl0uxKn2F3//03r 0vAtnn45ErYTigKrFmZ9mfeLS6ZTQgtADEV3leZ87gONAotpQX+oD5ETIHBko3p6v3dl b8Ag== X-Gm-Message-State: AOAM531++6x7ZIbG7rhyoYNop8fd6cHJ7E2shCJuV20AzepIxOvb6Bse OmrB8ZL6Gdgi+sE6l01fYg1feO9VWo0GHwqO7B0= X-Google-Smtp-Source: ABdhPJzi+z6KrrxRcyVmBGK4K6qI0YwfFskdGKirAKIKyHt0YoKnsJ/YqTzeHbO9SQWE7CMFfV69oN8rXUt99iBlnYU= X-Received: by 2002:ab0:3157:: with SMTP id e23mr27444457uam.106.1618423347408; Wed, 14 Apr 2021 11:02:27 -0700 (PDT) MIME-Version: 1.0 References: <20210412153754.235500-1-revest@chromium.org> <20210412153754.235500-4-revest@chromium.org> In-Reply-To: From: Geert Uytterhoeven Date: Wed, 14 Apr 2021 20:02:15 +0200 Message-ID: Subject: Re: [PATCH bpf-next v3 3/6] bpf: Add a bpf_snprintf helper To: Andrii Nakryiko Cc: Florent Revest , bpf , Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Yonghong Song , KP Singh , Brendan Jackman , open list Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Andrii, On Wed, Apr 14, 2021 at 9:41 AM Andrii Nakryiko wrote: > On Mon, Apr 12, 2021 at 8:38 AM Florent Revest wrote: > > The implementation takes inspiration from the existing bpf_trace_printk > > helper but there are a few differences: > > > > To allow for a large number of format-specifiers, parameters are > > provided in an array, like in bpf_seq_printf. > > > > Because the output string takes two arguments and the array of > > parameters also takes two arguments, the format string needs to fit in > > one argument. Thankfully, ARG_PTR_TO_CONST_STR is guaranteed to point to > > a zero-terminated read-only map so we don't need a format string length > > arg. > > > > Because the format-string is known at verification time, we also do > > a first pass of format string validation in the verifier logic. This > > makes debugging easier. > > > > Signed-off-by: Florent Revest > > --- > > include/linux/bpf.h | 6 ++++ > > include/uapi/linux/bpf.h | 28 +++++++++++++++++++ > > kernel/bpf/helpers.c | 2 ++ > > kernel/bpf/verifier.c | 41 ++++++++++++++++++++++++++++ > > kernel/trace/bpf_trace.c | 50 ++++++++++++++++++++++++++++++++++ > > tools/include/uapi/linux/bpf.h | 28 +++++++++++++++++++ > > 6 files changed, 155 insertions(+) > > > > [...] > > > diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c > > index 5f46dd6f3383..d4020e5f91ee 100644 > > --- a/kernel/bpf/verifier.c > > +++ b/kernel/bpf/verifier.c > > @@ -5918,6 +5918,41 @@ static int check_reference_leak(struct bpf_verifier_env *env) > > return state->acquired_refs ? -EINVAL : 0; > > } > > > > +static int check_bpf_snprintf_call(struct bpf_verifier_env *env, > > + struct bpf_reg_state *regs) > > +{ > > + struct bpf_reg_state *fmt_reg = ®s[BPF_REG_3]; > > + struct bpf_reg_state *data_len_reg = ®s[BPF_REG_5]; > > + struct bpf_map *fmt_map = fmt_reg->map_ptr; > > + int err, fmt_map_off, num_args; > > + u64 fmt_addr; > > + char *fmt; > > + > > + /* data must be an array of u64 */ > > + if (data_len_reg->var_off.value % 8) > > + return -EINVAL; > > + num_args = data_len_reg->var_off.value / 8; > > + > > + /* fmt being ARG_PTR_TO_CONST_STR guarantees that var_off is const > > + * and map_direct_value_addr is set. > > + */ > > + fmt_map_off = fmt_reg->off + fmt_reg->var_off.value; > > + err = fmt_map->ops->map_direct_value_addr(fmt_map, &fmt_addr, > > + fmt_map_off); > > + if (err) > > + return err; > > + fmt = (char *)fmt_addr + fmt_map_off; > > + > > bot complained about lack of (long) cast before fmt_addr, please address (uintptr_t), I assume? Gr{oetje,eeting}s, Geert -- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds