From patchwork Tue Apr 14 22:57:13 2015 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Alexei Starovoitov X-Patchwork-Id: 461295 X-Patchwork-Delegate: davem@davemloft.net Return-Path: X-Original-To: patchwork-incoming@ozlabs.org Delivered-To: patchwork-incoming@ozlabs.org Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by ozlabs.org (Postfix) with ESMTP id 07CC6140281 for ; Wed, 15 Apr 2015 08:57:30 +1000 (AEST) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754239AbbDNW50 (ORCPT ); Tue, 14 Apr 2015 18:57:26 -0400 Received: from mail-pd0-f174.google.com ([209.85.192.174]:36243 "EHLO mail-pd0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754179AbbDNW5Y (ORCPT ); Tue, 14 Apr 2015 18:57:24 -0400 Received: by pdea3 with SMTP id a3so28658544pde.3 for ; Tue, 14 Apr 2015 15:57:23 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:from:to:cc:subject:date:message-id; bh=zTWH4iEBhLMkkTT4UXpjtnZQsTlRE+9aXmu9RUw6z3Y=; b=ZEkXA5Hajrdd69womSTJIKMls4ncMPt5VvnPBGeApDGn4Mk9NYBw89K2krYtR0Va88 qdKIocTTbdCg5u/osKuFWsqp4Mc0BAgoUMnQVg4IaG0hdKdjnr2R1RCwBQIwvI2skXcI 6smntNS3QixhT/8TVLGNjIysiBkf01br/AHTPEowfPvHTwb3+KWWBbYtkPRvgpNRL13O ECfPN9wuqIO7siVfchnXP03sffir/8eaXuzU6gB6NAIiA8ZBnWqEJXT//Am8QPLjT/Kc T6dO5PlilBLcdszfl3GTGEFeU9TPqAHfdRP9fNiqTHgKYYR4cph6/1jYpCAjuf99M6HK szYw== X-Gm-Message-State: ALoCoQnq0FkkR2wOBquKnvIDRh6XhzmtRc8wGjiagxnP1fugobS4/1DyhtwFgSgdZarrmonfkKkH X-Received: by 10.66.252.3 with SMTP id zo3mr39740160pac.26.1429052243468; Tue, 14 Apr 2015 15:57:23 -0700 (PDT) Received: from localhost.localdomain ([12.229.56.227]) by mx.google.com with ESMTPSA id np6sm2096919pdb.80.2015.04.14.15.57.22 (version=TLSv1.1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Tue, 14 Apr 2015 15:57:22 -0700 (PDT) From: Alexei Starovoitov To: "David S. Miller" Cc: Daniel Borkmann , Hannes Frederic Sowa , netdev@vger.kernel.org Subject: [PATCH net] bpf: fix verifier memory corruption Date: Tue, 14 Apr 2015 15:57:13 -0700 Message-Id: <1429052233-8252-1-git-send-email-ast@plumgrid.com> X-Mailer: git-send-email 1.7.9.5 Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org Due to missing bounds check the DAG pass of the BPF verifier can corrupt the memory which can cause random crashes during program loading: [8.449451] BUG: unable to handle kernel paging request at ffffffffffffffff [8.451293] IP: [] kmem_cache_alloc_trace+0x8d/0x2f0 [8.452329] Oops: 0000 [#1] SMP [8.452329] Call Trace: [8.452329] [] bpf_check+0x852/0x2000 [8.452329] [] bpf_prog_load+0x1e4/0x310 [8.452329] [] ? might_fault+0x5f/0xb0 [8.452329] [] SyS_bpf+0x806/0xa30 Fixes: f1bca824dabb ("bpf: add search pruning optimization to verifier") Signed-off-by: Alexei Starovoitov Acked-by: Hannes Frederic Sowa Acked-by: Daniel Borkmann --- Many things need to align for this crash to be seen, yet I managed to hit it. In my case JA was last insn, 't' was 255 and explored_states array had 256 elements. I've double checked other similar paths and all seems clean. 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 a28e09c7825d..36508e69e92a 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -1380,7 +1380,8 @@ peek_stack: /* tell verifier to check for equivalent states * after every call and jump */ - env->explored_states[t + 1] = STATE_LIST_MARK; + if (t + 1 < insn_cnt) + env->explored_states[t + 1] = STATE_LIST_MARK; } else { /* conditional jump with two edges */ ret = push_insn(t, t + 1, FALLTHROUGH, env);