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=-9.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,UNPARSEABLE_RELAY, 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 2BA79C43381 for ; Thu, 21 Mar 2019 10:00:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id EDF1E218B0 for ; Thu, 21 Mar 2019 10:00:49 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728350AbfCUKAs (ORCPT ); Thu, 21 Mar 2019 06:00:48 -0400 Received: from out30-54.freemail.mail.aliyun.com ([115.124.30.54]:41844 "EHLO out30-54.freemail.mail.aliyun.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728325AbfCUKAq (ORCPT ); Thu, 21 Mar 2019 06:00:46 -0400 X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R391e4;CH=green;DM=||false|;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01e07487;MF=xuyu@linux.alibaba.com;NM=1;PH=DS;RN=4;SR=0;TI=SMTPD_---0TNGmqso_1553162437; Received: from localhost(mailfrom:xuyu@linux.alibaba.com fp:SMTPD_---0TNGmqso_1553162437) by smtp.aliyun-inc.com(127.0.0.1); Thu, 21 Mar 2019 18:00:43 +0800 From: Xu Yu To: daniel@iogearbox.net, bpf@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH v2] bpf: do not restore dst_reg when cur_state is freed Date: Thu, 21 Mar 2019 18:00:35 +0800 Message-Id: X-Mailer: git-send-email 1.8.3.1 In-Reply-To: References: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Syzkaller hit 'KASAN: use-after-free Write in sanitize_ptr_alu' bug. Call trace: dump_stack+0xbf/0x12e print_address_description+0x6a/0x280 kasan_report+0x237/0x360 sanitize_ptr_alu+0x85a/0x8d0 adjust_ptr_min_max_vals+0x8f2/0x1ca0 adjust_reg_min_max_vals+0x8ed/0x22e0 do_check+0x1ca6/0x5d00 bpf_check+0x9ca/0x2570 bpf_prog_load+0xc91/0x1030 __se_sys_bpf+0x61e/0x1f00 do_syscall_64+0xc8/0x550 entry_SYSCALL_64_after_hwframe+0x49/0xbe Fault injection trace:  kfree+0xea/0x290  free_func_state+0x4a/0x60  free_verifier_state+0x61/0xe0  push_stack+0x216/0x2f0 <- inject failslab  sanitize_ptr_alu+0x2b1/0x8d0  adjust_ptr_min_max_vals+0x8f2/0x1ca0  adjust_reg_min_max_vals+0x8ed/0x22e0  do_check+0x1ca6/0x5d00  bpf_check+0x9ca/0x2570  bpf_prog_load+0xc91/0x1030  __se_sys_bpf+0x61e/0x1f00  do_syscall_64+0xc8/0x550  entry_SYSCALL_64_after_hwframe+0x49/0xbe When kzalloc() fails in push_stack(), free_verifier_state() will free current verifier state. As push_stack() returns, dst_reg was restored if ptr_is_dst_reg is false. However, as member of the cur_state, dst_reg is also freed, and error occurs when dereferencing dst_reg. Simply fix it by testing ret of push_stack() before retoring dst_reg. Signed-off-by: Xu Yu --- kernel/bpf/verifier.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index ce166a0..cb1b874 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -3368,7 +3368,7 @@ static int sanitize_ptr_alu(struct bpf_verifier_env *env, *dst_reg = *ptr_reg; } ret = push_stack(env, env->insn_idx + 1, env->insn_idx, true); - if (!ptr_is_dst_reg) + if (!ptr_is_dst_reg && ret) *dst_reg = tmp; return !ret ? -EFAULT : 0; } -- 1.8.3.1