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 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id B12ACC433EF for ; Thu, 30 Sep 2021 12:14:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 88DC4613A6 for ; Thu, 30 Sep 2021 12:14:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1348399AbhI3MQI (ORCPT ); Thu, 30 Sep 2021 08:16:08 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59750 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1348201AbhI3MQI (ORCPT ); Thu, 30 Sep 2021 08:16:08 -0400 Received: from mail-yb1-xb2b.google.com (mail-yb1-xb2b.google.com [IPv6:2607:f8b0:4864:20::b2b]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 094BAC06176A; Thu, 30 Sep 2021 05:14:26 -0700 (PDT) Received: by mail-yb1-xb2b.google.com with SMTP id r1so12607426ybo.10; Thu, 30 Sep 2021 05:14:26 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=1ly6d2NRz/CO4e+/occWByJ+1ybkH2AhzgC827GNKok=; b=D3yALrGFWCHoJefkI8XjZMKrwZ18ui6XDMw4t95SVu6n4b+QlQDXUbKuYqj+3ZUR77 4OraB2xwKiXlxZZNnGmNOHTq5acSirqEeu5hMoj3h8R24v2FpumBTvNIfEGIUIDjTWke dkjas9WJSrST1VbmPCOntur+clVa23wWWI2RAVuGhzrik9BskkbnlF3cScob9/OZa++q zXE7q1BSlOymhD3sKQLngpY0g741BFHsJFuU/FMsebpo+A1PiQtm3o24bcLml9xVln5K mrZ0oBecfxxCxRSmjBC9vfAJ90S8NFMZroKhANmw42yTzYnnMAF+9h8wraYhzlLDGKFA usSQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=1ly6d2NRz/CO4e+/occWByJ+1ybkH2AhzgC827GNKok=; b=6pQCy3Mz9Ed8lQbEZNRY59215zyoScAKpxk9w8IJMOBESr0+Yd9RF/WUL1zHUZKCXj pxOpEuAKHVpgKU01ihekITnqDM9MHtfws9wy3tHeRP2XaHlNPPhns9h8RfxY4M4FYwYT iLFQ660BxVWNWq5zsA2sU+qoPE+U0PhEExLEt8Vn+6OzyhHWBaR9etB1hPZDtq+VGuBt QVzWgJXjonnhOJgJspECOmhc92aN9vNxHcFBidgPKSmiIXEI7uGEzEWHTNjgvJuOcCww ibvGBJbnlmR8AdfMhgU9rtemxQ6+uuZxUpTEVg9kOzEDkDiEfyG0jZQsR7iEOzpcsPS5 fJCQ== X-Gm-Message-State: AOAM530A6wYG0clXk9FoWtIDr7zgtbxN+GCbZk+C8fQREasNAO2Yl8Os 22ejaHgj0QmgWuUhvRF0+qKZ9qHP1V6Tw0CLJ8o= X-Google-Smtp-Source: ABdhPJx8FtzrbD51HUmiENPFGgET25pOeR5F1yAAzL7J7koVSiUqSLdK0Jmqh5ZoQDDR0cyJLgayWISpxy8Dt9tMI4E= X-Received: by 2002:a25:515:: with SMTP id 21mr6157057ybf.279.1633004065280; Thu, 30 Sep 2021 05:14:25 -0700 (PDT) MIME-Version: 1.0 References: <20210925053106.1031798-1-th.yasumatsu@gmail.com> <9be5acb8-5eaa-6101-1be8-a74d7df7e20e@iogearbox.net> In-Reply-To: <9be5acb8-5eaa-6101-1be8-a74d7df7e20e@iogearbox.net> From: Tatushiko Yasumatsu Date: Thu, 30 Sep 2021 21:14:14 +0900 Message-ID: Subject: Re: [PATCH] bpf: Fix integer overflow in prealloc_elems_and_freelist() To: Daniel Borkmann Cc: Alexei Starovoitov , Andrii Nakryiko , Martin KaFai Lau , Song Liu , Yonghong Song , John Fastabend , KP Singh , netdev@vger.kernel.org, bpf@vger.kernel.org, linux-kernel@vger.kernel.org, Tatushiko Yasumatsu Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org On Tue, Sep 28, 2021 at 02:29:43PM +0200, Daniel Borkmann wrote: > On 9/25/21 7:31 AM, Tatsuhiko Yasumatsu wrote: > > In prealloc_elems_and_freelist(), the multiplication to calculate the > > size passed to bpf_map_area_alloc() could lead to an integer overflow. > > As a result, out-of-bounds write could occur in pcpu_freelist_populate() > > as reported by KASAN: > > > > [...] > > [ 16.968613] BUG: KASAN: slab-out-of-bounds in pcpu_freelist_populate+0xd9/0x100 > > [ 16.969408] Write of size 8 at addr ffff888104fc6ea0 by task crash/78 > > [ 16.970038] > > [ 16.970195] CPU: 0 PID: 78 Comm: crash Not tainted 5.15.0-rc2+ #1 > > [ 16.970878] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.13.0-1ubuntu1.1 04/01/2014 > > [ 16.972026] Call Trace: > > [ 16.972306] dump_stack_lvl+0x34/0x44 > > [ 16.972687] print_address_description.constprop.0+0x21/0x140 > > [ 16.973297] ? pcpu_freelist_populate+0xd9/0x100 > > [ 16.973777] ? pcpu_freelist_populate+0xd9/0x100 > > [ 16.974257] kasan_report.cold+0x7f/0x11b > > [ 16.974681] ? pcpu_freelist_populate+0xd9/0x100 > > [ 16.975190] pcpu_freelist_populate+0xd9/0x100 > > [ 16.975669] stack_map_alloc+0x209/0x2a0 > > [ 16.976106] __sys_bpf+0xd83/0x2ce0 > > [...] > > > > The possibility of this overflow was originally discussed in [0], but > > was overlooked. > > > > Fix the integer overflow by casting one operand to u64. > > > > [0] https://lore.kernel.org/bpf/728b238e-a481-eb50-98e9-b0f430ab01e7@gmail.com/ > > > > Fixes: 557c0c6e7df8 ("bpf: convert stackmap to pre-allocation") > > Signed-off-by: Tatsuhiko Yasumatsu > > --- > > kernel/bpf/stackmap.c | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/kernel/bpf/stackmap.c b/kernel/bpf/stackmap.c > > index 09a3fd97d329..8941dc83a769 100644 > > --- a/kernel/bpf/stackmap.c > > +++ b/kernel/bpf/stackmap.c > > @@ -66,7 +66,7 @@ static int prealloc_elems_and_freelist(struct bpf_stack_map *smap) > > u32 elem_size = sizeof(struct stack_map_bucket) + smap->map.value_size; > > Thanks a lot for the fix, Tatsuhiko! Could we just change the above elem_size to u64 instead? Thank you for your review, Daniel! Yes, I think it's possible to just change elem_size to u64. We just have to be careful to cast one operand (smap->map.value_size) to u64, so that the integer overflow won't happen in 32-bit architectures. This is necessary because in 32-bit architectures, the result of sizeof() is a 32-bit integer. I will update the patch. > > > int err; > > - smap->elems = bpf_map_area_alloc(elem_size * smap->map.max_entries, > > + smap->elems = bpf_map_area_alloc((u64)elem_size * smap->map.max_entries, > > smap->map.numa_node); > > if (!smap->elems) > > return -ENOMEM; > > > > Best, > Daniel Best regards, Tatsuhiko Yasumatsu