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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8CBACC4332F for ; Thu, 15 Dec 2022 21:45:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229634AbiLOVpF (ORCPT ); Thu, 15 Dec 2022 16:45:05 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43252 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229460AbiLOVpE (ORCPT ); Thu, 15 Dec 2022 16:45:04 -0500 Received: from sin.source.kernel.org (sin.source.kernel.org [145.40.73.55]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 92D435C76F for ; Thu, 15 Dec 2022 13:45:02 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by sin.source.kernel.org (Postfix) with ESMTPS id 079F7CE1D57 for ; Thu, 15 Dec 2022 21:45:01 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id F251DC433EF; Thu, 15 Dec 2022 21:44:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1671140699; bh=bmSpbFUzBfCJTJ+XALCMTiNU3j80LfNB9mVXE7hJfDM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=hkItxWhN6k6ZCZ713wWX1OjxD0V28UFzMosKrgE4vJ/nloVdArBE/GphpiuIiaSiQ jLBBk819u9M5f/DSYkH7728wajfPtXm4xw6okGez8dDbJ4HGid5olsm/4NZg0stR79 M2FL1czsmOSNQlYB0IeCZbSaNsl3Nz0cYU/X74P5pJETlkGATytXTeEWI+Ui0Q4mVa HYk4r7gQsWXqahwEqoOvnZ+NKTti192I70f6p47wE8j9qk0XX77U7jLaDh//vr2DvM rkT55TdHB8BSNzoO1SjI6vZ7ehlJgcDpfmPDoUwdg9vYqaXxiDd+b7CKE9yZaVQ71k k2Hb2TywKN1xw== From: Jiri Olsa To: Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko Cc: bpf@vger.kernel.org, Martin KaFai Lau , Song Liu , Yonghong Song , John Fastabend , KP Singh , Stanislav Fomichev , Hao Luo , Florent Revest Subject: [PATCHv3 bpf-next 2/3] bpf: Do cleanup in bpf_bprintf_cleanup only when needed Date: Thu, 15 Dec 2022 22:44:29 +0100 Message-Id: <20221215214430.1336195-3-jolsa@kernel.org> X-Mailer: git-send-email 2.38.1 In-Reply-To: <20221215214430.1336195-1-jolsa@kernel.org> References: <20221215214430.1336195-1-jolsa@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org Currently we always cleanup/decrement bpf_bprintf_nest_level variable in bpf_bprintf_cleanup if it's > 0. There's possible scenario where this could cause a problem, when bpf_bprintf_prepare does not get bin_args buffer (because num_args is 0) and following bpf_bprintf_cleanup call decrements bpf_bprintf_nest_level variable, like: in task context: bpf_bprintf_prepare(num_args != 0) increments 'bpf_bprintf_nest_level = 1' -> first irq : bpf_bprintf_prepare(num_args == 0) bpf_bprintf_cleanup decrements 'bpf_bprintf_nest_level = 0' -> second irq: bpf_bprintf_prepare(num_args != 0) bpf_bprintf_nest_level = 1 gets same buffer as task context above Adding check to bpf_bprintf_cleanup and doing the real cleanup only if we got bin_args data in the first place. Signed-off-by: Jiri Olsa --- include/linux/bpf.h | 2 +- kernel/bpf/helpers.c | 16 +++++++++------- kernel/trace/bpf_trace.c | 6 +++--- 3 files changed, 13 insertions(+), 11 deletions(-) diff --git a/include/linux/bpf.h b/include/linux/bpf.h index cc390ba32e70..656879385fbf 100644 --- a/include/linux/bpf.h +++ b/include/linux/bpf.h @@ -2803,7 +2803,7 @@ struct bpf_bprintf_data { int bpf_bprintf_prepare(char *fmt, u32 fmt_size, const u64 *raw_args, u32 num_args, struct bpf_bprintf_data *data); -void bpf_bprintf_cleanup(void); +void bpf_bprintf_cleanup(struct bpf_bprintf_data *data); /* the implementation of the opaque uapi struct bpf_dynptr */ struct bpf_dynptr_kern { diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c index 7dbf6bb72cad..9cca02e13f2e 100644 --- a/kernel/bpf/helpers.c +++ b/kernel/bpf/helpers.c @@ -784,12 +784,14 @@ static int try_get_fmt_tmp_buf(char **tmp_buf) return 0; } -void bpf_bprintf_cleanup(void) +void bpf_bprintf_cleanup(struct bpf_bprintf_data *data) { - if (this_cpu_read(bpf_bprintf_nest_level)) { - this_cpu_dec(bpf_bprintf_nest_level); - preempt_enable(); - } + if (!data->bin_args) + return; + if (WARN_ON_ONCE(this_cpu_read(bpf_bprintf_nest_level) == 0)) + return; + this_cpu_dec(bpf_bprintf_nest_level); + preempt_enable(); } /* @@ -1021,7 +1023,7 @@ int bpf_bprintf_prepare(char *fmt, u32 fmt_size, const u64 *raw_args, err = 0; out: if (err) - bpf_bprintf_cleanup(); + bpf_bprintf_cleanup(data); return err; } @@ -1047,7 +1049,7 @@ BPF_CALL_5(bpf_snprintf, char *, str, u32, str_size, char *, fmt, err = bstr_printf(str, str_size, fmt, data.bin_args); - bpf_bprintf_cleanup(); + bpf_bprintf_cleanup(&data); return err + 1; } diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c index 3e849c3a7cc8..2129f7c68bb5 100644 --- a/kernel/trace/bpf_trace.c +++ b/kernel/trace/bpf_trace.c @@ -396,7 +396,7 @@ BPF_CALL_5(bpf_trace_printk, char *, fmt, u32, fmt_size, u64, arg1, trace_bpf_trace_printk(buf); raw_spin_unlock_irqrestore(&trace_printk_lock, flags); - bpf_bprintf_cleanup(); + bpf_bprintf_cleanup(&data); return ret; } @@ -454,7 +454,7 @@ BPF_CALL_4(bpf_trace_vprintk, char *, fmt, u32, fmt_size, const void *, args, trace_bpf_trace_printk(buf); raw_spin_unlock_irqrestore(&trace_printk_lock, flags); - bpf_bprintf_cleanup(); + bpf_bprintf_cleanup(&data); return ret; } @@ -494,7 +494,7 @@ BPF_CALL_5(bpf_seq_printf, struct seq_file *, m, char *, fmt, u32, fmt_size, seq_bprintf(m, fmt, data.bin_args); - bpf_bprintf_cleanup(); + bpf_bprintf_cleanup(&data); return seq_has_overflowed(m) ? -EOVERFLOW : 0; } -- 2.38.1