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 853DAC433EF for ; Tue, 28 Sep 2021 12:29:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6604F60F21 for ; Tue, 28 Sep 2021 12:29:50 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240673AbhI1Mb2 (ORCPT ); Tue, 28 Sep 2021 08:31:28 -0400 Received: from www62.your-server.de ([213.133.104.62]:45144 "EHLO www62.your-server.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S240571AbhI1Mb2 (ORCPT ); Tue, 28 Sep 2021 08:31:28 -0400 Received: from [78.46.152.42] (helo=sslproxy04.your-server.de) by www62.your-server.de with esmtpsa (TLSv1.3:TLS_AES_256_GCM_SHA384:256) (Exim 4.92.3) (envelope-from ) id 1mVCEx-000Gn4-TZ; Tue, 28 Sep 2021 14:29:43 +0200 Received: from [85.1.206.226] (helo=linux.home) by sslproxy04.your-server.de with esmtpsa (TLSv1.3:TLS_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1mVCEx-000W89-La; Tue, 28 Sep 2021 14:29:43 +0200 Subject: Re: [PATCH] bpf: Fix integer overflow in prealloc_elems_and_freelist() To: Tatsuhiko Yasumatsu , Alexei Starovoitov , Andrii Nakryiko Cc: Martin KaFai Lau , Song Liu , Yonghong Song , John Fastabend , KP Singh , netdev@vger.kernel.org, bpf@vger.kernel.org, linux-kernel@vger.kernel.org References: <20210925053106.1031798-1-th.yasumatsu@gmail.com> From: Daniel Borkmann Message-ID: <9be5acb8-5eaa-6101-1be8-a74d7df7e20e@iogearbox.net> Date: Tue, 28 Sep 2021 14:29:43 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.7.2 MIME-Version: 1.0 In-Reply-To: <20210925053106.1031798-1-th.yasumatsu@gmail.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Authenticated-Sender: daniel@iogearbox.net X-Virus-Scanned: Clear (ClamAV 0.103.3/26306/Tue Sep 28 11:05:37 2021) Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org 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? > 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