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[209.132.180.67]) by mx.google.com with ESMTP id g2si3884751plo.354.2019.03.21.01.34.36; Thu, 21 Mar 2019 01:34:51 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Authentication-Results: mx.google.com; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=alibaba.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727993AbfCUIcl (ORCPT + 99 others); Thu, 21 Mar 2019 04:32:41 -0400 Received: from out4436.biz.mail.alibaba.com ([47.88.44.36]:6271 "EHLO out4436.biz.mail.alibaba.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727874AbfCUIcl (ORCPT ); Thu, 21 Mar 2019 04:32:41 -0400 X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R971e4;CH=green;DM=||false|;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01e07488;MF=xuyu@linux.alibaba.com;NM=1;PH=DS;RN=3;SR=0;TI=SMTPD_---0TNGaMx1_1553157149; Received: from localhost(mailfrom:xuyu@linux.alibaba.com fp:SMTPD_---0TNGaMx1_1553157149) by smtp.aliyun-inc.com(127.0.0.1); Thu, 21 Mar 2019 16:32:38 +0800 From: Xu Yu To: bpf@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH] bpf: do not restore dst_reg when cur_state is freed Date: Thu, 21 Mar 2019 16:31:33 +0800 Message-Id: X-Mailer: git-send-email 1.8.3.1 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 checking whether cur_state is NULL 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..018ce4f 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 && env->cur_state) *dst_reg = tmp; return !ret ? -EFAULT : 0; } -- 1.8.3.1