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=-17.4 required=3.0 tests=DKIMWL_WL_MED,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_GIT,USER_IN_DEF_DKIM_WL 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 BA4E9C7618E for ; Tue, 23 Jul 2019 10:15:49 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 92BA5223BE for ; Tue, 23 Jul 2019 10:15:49 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="XYpJc1p8" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2388938AbfGWKPs (ORCPT ); Tue, 23 Jul 2019 06:15:48 -0400 Received: from mail-pl1-f202.google.com ([209.85.214.202]:40657 "EHLO mail-pl1-f202.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2388924AbfGWKPs (ORCPT ); Tue, 23 Jul 2019 06:15:48 -0400 Received: by mail-pl1-f202.google.com with SMTP id 91so21681500pla.7 for ; Tue, 23 Jul 2019 03:15:47 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:in-reply-to:message-id:mime-version:references:subject:from:to :cc; bh=OnKPbl94vVh+VvHbMFFOkzGcpjhJxtsb+O1+2r/rSg8=; b=XYpJc1p8s+u2P+0doG/v++WGs+vUcbD7soscNcGUurYk3LLHhKjRCc5Xv46bUK45cR MjAQOUUwWVzOnjYCS0ztQa1xZuY8zrudmmBxTRzGFKM1ecsq6xM8+7wYavXVpDoY77uO 0pKA2bfvMQvHUxIx5uCu24U4bSVpNrKwoJ8X/lIyN+IfWXRxu8gStHlTkn0QwTIP1DQI oi1G4nHb5SV3BZ8vCkPXVaql7962JuGvHZYjYY8HgkE+KHgWtkiFzEJ0Lp+qznuAu9yq HRjstY7SkP3Wm2Nlrdk6PnrP/RFBdpeANl4wVWl9urPTQs0tePHL/n+1IhYtlrOS9m/y 8jtg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:in-reply-to:message-id:mime-version :references:subject:from:to:cc; bh=OnKPbl94vVh+VvHbMFFOkzGcpjhJxtsb+O1+2r/rSg8=; b=ExoWbqXlzQ1ouiiddSjS2DXwRq/hLsPdn3GyLqkivfR3jB94dtcJAQa9Lp3Ay4zfYi t5KXD5IUR0+2WS3nlBM832qDU0a068LaIiFJhMTeCR+fELQTLXLH6Zhbv+v8Nghj+SnZ MuO9d2E9q54JxmB4zbpo/F2/ZWlpDnVuOoFyOmxzthrrLYlQMkgPdlsH2jIQ2T/8icti XddFSkpWyzno86QW5Gia+adPtmt/KVtEQXAOi6IjZX30jmAPoblA9/DL/9qKjw7rA/1U qIBtA1//D7HIYdMqkj5ueVqD8oHwpilumyBmVC13bEFz4TtYZ7jdK/YsHLlGATPK+D+a /e7A== X-Gm-Message-State: APjAAAXkOZ0hstzXYo8pU0UqwnRYkhRlYrs27/6DjJvcjCvKD2c2sr8B cn87QXABzPgpwUVYtwmiYiC8bMFIDsw4cA== X-Google-Smtp-Source: APXvYqyxd+1+riabN28Jm79t5uXtvtNynhCUjlIeLWDSSABRRBBdV6JiwhphYs0UJ7daP7X2HiI2034BQKaYqA== X-Received: by 2002:a63:ec48:: with SMTP id r8mr879390pgj.387.1563876947240; Tue, 23 Jul 2019 03:15:47 -0700 (PDT) Date: Tue, 23 Jul 2019 03:15:37 -0700 In-Reply-To: <20190723101538.136328-1-edumazet@google.com> Message-Id: <20190723101538.136328-2-edumazet@google.com> Mime-Version: 1.0 References: <20190723101538.136328-1-edumazet@google.com> X-Mailer: git-send-email 2.22.0.657.g960e92d24f-goog Subject: [PATCH bpf 1/2] bpf: fix access to skb_shared_info->gso_segs From: Eric Dumazet To: Alexei Starovoitov , Daniel Borkmann Cc: "David S . Miller" , netdev , Eric Dumazet , Eric Dumazet , Stanislav Fomichev , bpf , syzbot Content-Type: text/plain; charset="UTF-8" Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org It is possible we reach bpf_convert_ctx_access() with si->dst_reg == si->src_reg Therefore, we need to load BPF_REG_AX before eventually mangling si->src_reg. syzbot generated this x86 code : 3: 55 push %rbp 4: 48 89 e5 mov %rsp,%rbp 7: 48 81 ec 00 00 00 00 sub $0x0,%rsp // Might be avoided ? e: 53 push %rbx f: 41 55 push %r13 11: 41 56 push %r14 13: 41 57 push %r15 15: 6a 00 pushq $0x0 17: 31 c0 xor %eax,%eax 19: 48 8b bf c0 00 00 00 mov 0xc0(%rdi),%rdi 20: 44 8b 97 bc 00 00 00 mov 0xbc(%rdi),%r10d 27: 4c 01 d7 add %r10,%rdi 2a: 48 0f b7 7f 06 movzwq 0x6(%rdi),%rdi // Crash 2f: 5b pop %rbx 30: 41 5f pop %r15 32: 41 5e pop %r14 34: 41 5d pop %r13 36: 5b pop %rbx 37: c9 leaveq 38: c3 retq Fixes: d9ff286a0f59 ("bpf: allow BPF programs access skb_shared_info->gso_segs field") Signed-off-by: Eric Dumazet Reported-by: syzbot --- net/core/filter.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/net/core/filter.c b/net/core/filter.c index 4e2a79b2fd77f36ba2a31e9e43af1abc1207766e..7878f918b8c057b7b90ca0afcf2d5773cfb55e15 100644 --- a/net/core/filter.c +++ b/net/core/filter.c @@ -7455,12 +7455,12 @@ static u32 bpf_convert_ctx_access(enum bpf_access_type type, case offsetof(struct __sk_buff, gso_segs): /* si->dst_reg = skb_shinfo(SKB); */ #ifdef NET_SKBUFF_DATA_USES_OFFSET - *insn++ = BPF_LDX_MEM(BPF_FIELD_SIZEOF(struct sk_buff, head), - si->dst_reg, si->src_reg, - offsetof(struct sk_buff, head)); *insn++ = BPF_LDX_MEM(BPF_FIELD_SIZEOF(struct sk_buff, end), BPF_REG_AX, si->src_reg, offsetof(struct sk_buff, end)); + *insn++ = BPF_LDX_MEM(BPF_FIELD_SIZEOF(struct sk_buff, head), + si->dst_reg, si->src_reg, + offsetof(struct sk_buff, head)); *insn++ = BPF_ALU64_REG(BPF_ADD, si->dst_reg, BPF_REG_AX); #else *insn++ = BPF_LDX_MEM(BPF_FIELD_SIZEOF(struct sk_buff, end), -- 2.22.0.657.g960e92d24f-goog