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=-19.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_GIT 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 B441AC433ED for ; Mon, 26 Apr 2021 07:52:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 821AF6105A for ; Mon, 26 Apr 2021 07:52:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233017AbhDZHxE (ORCPT ); Mon, 26 Apr 2021 03:53:04 -0400 Received: from mail.kernel.org ([198.145.29.99]:56118 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233357AbhDZHne (ORCPT ); Mon, 26 Apr 2021 03:43:34 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 6A77B613B2; Mon, 26 Apr 2021 07:39:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1619422793; bh=fXYI7LkxEUEiQL+M9Fyog+fr9/YAJ+bUjLFnHYnJaIE=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=gbixGl6dX++pCqsTeMinf4jYuBHjh9x/xcxb8jEoNLQAUVc+7AjyKsfAvtRhAb0CQ 7HCowttJrIsLyBio9clE3k18xaBqOsGHxQW/cmPGJF4jDfBZNmeLuRARQgkUH9HDlB ZGd4X4s2f+2nXBovFcXyG7iE9FWStOE5NwwDlqM0= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Song Liu , Alexei Starovoitov , Yonghong Song , Daniel Borkmann , Sasha Levin Subject: [PATCH 5.10 09/36] bpf: Permits pointers on stack for helper calls Date: Mon, 26 Apr 2021 09:29:51 +0200 Message-Id: <20210426072819.114779832@linuxfoundation.org> X-Mailer: git-send-email 2.31.1 In-Reply-To: <20210426072818.777662399@linuxfoundation.org> References: <20210426072818.777662399@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Yonghong Song [ Upstream commit cd17d38f8b28f808c368121041c0a4fa91757e0d ] Currently, when checking stack memory accessed by helper calls, for spills, only PTR_TO_BTF_ID and SCALAR_VALUE are allowed. Song discovered an issue where the below bpf program int dump_task(struct bpf_iter__task *ctx) { struct seq_file *seq = ctx->meta->seq; static char[] info = "abc"; BPF_SEQ_PRINTF(seq, "%s\n", info); return 0; } may cause a verifier failure. The verifier output looks like: ; struct seq_file *seq = ctx->meta->seq; 1: (79) r1 = *(u64 *)(r1 +0) ; BPF_SEQ_PRINTF(seq, "%s\n", info); 2: (18) r2 = 0xffff9054400f6000 4: (7b) *(u64 *)(r10 -8) = r2 5: (bf) r4 = r10 ; 6: (07) r4 += -8 ; BPF_SEQ_PRINTF(seq, "%s\n", info); 7: (18) r2 = 0xffff9054400fe000 9: (b4) w3 = 4 10: (b4) w5 = 8 11: (85) call bpf_seq_printf#126 R1_w=ptr_seq_file(id=0,off=0,imm=0) R2_w=map_value(id=0,off=0,ks=4,vs=4,imm=0) R3_w=inv4 R4_w=fp-8 R5_w=inv8 R10=fp0 fp-8_w=map_value last_idx 11 first_idx 0 regs=8 stack=0 before 10: (b4) w5 = 8 regs=8 stack=0 before 9: (b4) w3 = 4 invalid indirect read from stack off -8+0 size 8 Basically, the verifier complains the map_value pointer at "fp-8" location. To fix the issue, if env->allow_ptr_leaks is true, let us also permit pointers on the stack to be accessible by the helper. Reported-by: Song Liu Suggested-by: Alexei Starovoitov Signed-off-by: Yonghong Song Signed-off-by: Daniel Borkmann Acked-by: Song Liu Link: https://lore.kernel.org/bpf/20201210013349.943719-1-yhs@fb.com Signed-off-by: Sasha Levin --- kernel/bpf/verifier.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 3370f0d476e9..2e09e691a6be 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -3759,7 +3759,8 @@ static int check_stack_boundary(struct bpf_verifier_env *env, int regno, goto mark; if (state->stack[spi].slot_type[0] == STACK_SPILL && - state->stack[spi].spilled_ptr.type == SCALAR_VALUE) { + (state->stack[spi].spilled_ptr.type == SCALAR_VALUE || + env->allow_ptr_leaks)) { __mark_reg_unknown(env, &state->stack[spi].spilled_ptr); for (j = 0; j < BPF_REG_SIZE; j++) state->stack[spi].slot_type[j] = STACK_MISC; -- 2.30.2