linux-kernel - Re: [syzbot] [bpf?] UBSAN: array-index-out-of-bounds in bpf_mprog

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Message-ID: <2bea40de-81e5-10a8-8422-efd79a2fa3a5@iogearbox.net>
Date:   Fri, 4 Aug 2023 15:15:06 +0200
From:   Daniel Borkmann <daniel@...earbox.net>
To:     Martin KaFai Lau <martin.lau@...ux.dev>,
        syzbot <syzbot+0c06ba0f831fe07a8f27@...kaller.appspotmail.com>,
        syzkaller-bugs@...glegroups.com, bpf@...r.kernel.org
Cc:     andrii@...nel.org, ast@...nel.org, haoluo@...gle.com,
        john.fastabend@...il.com, jolsa@...nel.org, kpsingh@...nel.org,
        linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
        sdf@...gle.com, song@...nel.org, yhs@...com
Subject: Re: [syzbot] [bpf?] UBSAN: array-index-out-of-bounds in
 bpf_mprog_detach

On 8/4/23 1:39 AM, Martin KaFai Lau wrote:
> On 7/29/23 5:48 PM, syzbot wrote:
>> syzbot found the following issue on:
>>
>> HEAD commit:    ec87f05402f5 octeontx2-af: Install TC filter rules in hard..
>> git tree:       net-next
>> console output:https://syzkaller.appspot.com/x/log.txt?x=12a76df1a80000
>> kernel config:https://syzkaller.appspot.com/x/.config?x=8acaeb93ad7c6aaa
>> dashboard link:https://syzkaller.appspot.com/bug?extid=0c06ba0f831fe07a8f27
>> compiler:       gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
>>
>> Unfortunately, I don't have any reproducer for this issue yet.
>>
>> Downloadable assets:
>> disk image:https://storage.googleapis.com/syzbot-assets/0fc53904fc08/disk-ec87f054.raw.xz
>> vmlinux:https://storage.googleapis.com/syzbot-assets/aee64718ea5c/vmlinux-ec87f054.xz
>> kernel image:https://storage.googleapis.com/syzbot-assets/d3b6d3f4cfbc/bzImage-ec87f054.xz
>>
>> IMPORTANT: if you fix the issue, please add the following tag to the commit:
>> Reported-by:syzbot+0c06ba0f831fe07a8f27@...kaller.appspotmail.com
>>
>> ================================================================================
>> UBSAN: array-index-out-of-bounds in ./include/linux/bpf_mprog.h:292:24
>> index 4294967295 is out of range for type 'bpf_mprog_fp [64]'
>> CPU: 1 PID: 13232 Comm: syz-executor.1 Not tainted 6.5.0-rc2-syzkaller-00573-gec87f05402f5 #0
>> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2023
>> Call Trace:
>>   <TASK>
>>   __dump_stack lib/dump_stack.c:88 [inline]
>>   dump_stack_lvl+0x125/0x1b0 lib/dump_stack.c:106
>>   ubsan_epilogue lib/ubsan.c:217 [inline]
>>   __ubsan_handle_out_of_bounds+0x111/0x150 lib/ubsan.c:348
>>   bpf_mprog_read include/linux/bpf_mprog.h:292 [inline]
>>   bpf_mprog_fetch kernel/bpf/mprog.c:307 [inline]
>>   bpf_mprog_detach+0xcd7/0xd50 kernel/bpf/mprog.c:381
>>   tcx_prog_detach+0x258/0x950 kernel/bpf/tcx.c:78
>>   bpf_prog_detach kernel/bpf/syscall.c:3877 [inline]
>>   __sys_bpf+0x36ee/0x4ec0 kernel/bpf/syscall.c:5357

Was able to repro, fix + selftest is here:
https://lore.kernel.org/bpf/20230804131112.11012-1-daniel@iogearbox.net/

Thanks,
Daniel