From: Daniel Borkmann <daniel@iogearbox.net>
To: Andrii Nakryiko <andrii.nakryiko@gmail.com>,
Lorenz Bauer <lmb@cloudflare.com>
Cc: Alexei Starovoitov <ast@kernel.org>,
Andrii Nakryiko <andrii@kernel.org>,
"David S. Miller" <davem@davemloft.net>,
Jakub Kicinski <kuba@kernel.org>,
Jesper Dangaard Brouer <hawk@kernel.org>,
John Fastabend <john.fastabend@gmail.com>,
kernel-team <kernel-team@cloudflare.com>,
Andrii Nakryiko <andriin@fb.com>,
Networking <netdev@vger.kernel.org>, bpf <bpf@vger.kernel.org>,
open list <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH bpf] bpf: fix OOB read when printing XDP link fdinfo
Date: Fri, 16 Jul 2021 23:00:58 +0200 [thread overview]
Message-ID: <7854fbef-8ea5-5396-6369-99eef1dcccaa@iogearbox.net> (raw)
In-Reply-To: <CAEf4BzauzWhNag0z31krN_MTZTGLynAJvkh_7P3yLQCx5XLTAg@mail.gmail.com>
On 7/16/21 10:43 PM, Andrii Nakryiko wrote:
> On Fri, Jul 16, 2021 at 3:05 AM Lorenz Bauer <lmb@cloudflare.com> wrote:
>>
>> We got the following UBSAN report on one of our testing machines:
>>
>> ================================================================================
>> UBSAN: array-index-out-of-bounds in kernel/bpf/syscall.c:2389:24
>> index 6 is out of range for type 'char *[6]'
>> CPU: 43 PID: 930921 Comm: systemd-coredum Tainted: G O 5.10.48-cloudflare-kasan-2021.7.0 #1
>> Hardware name: <snip>
>> Call Trace:
>> dump_stack+0x7d/0xa3
>> ubsan_epilogue+0x5/0x40
>> __ubsan_handle_out_of_bounds.cold+0x43/0x48
>> ? seq_printf+0x17d/0x250
>> bpf_link_show_fdinfo+0x329/0x380
>> ? bpf_map_value_size+0xe0/0xe0
>> ? put_files_struct+0x20/0x2d0
>> ? __kasan_kmalloc.constprop.0+0xc2/0xd0
>> seq_show+0x3f7/0x540
>> seq_read_iter+0x3f8/0x1040
>> seq_read+0x329/0x500
>> ? seq_read_iter+0x1040/0x1040
>> ? __fsnotify_parent+0x80/0x820
>> ? __fsnotify_update_child_dentry_flags+0x380/0x380
>> vfs_read+0x123/0x460
>> ksys_read+0xed/0x1c0
>> ? __x64_sys_pwrite64+0x1f0/0x1f0
>> do_syscall_64+0x33/0x40
>> entry_SYSCALL_64_after_hwframe+0x44/0xa9
>> <snip>
>> ================================================================================
>> ================================================================================
>> UBSAN: object-size-mismatch in kernel/bpf/syscall.c:2384:2
>>
>> From the report, we can infer that some array access in bpf_link_show_fdinfo at index 6
>> is out of bounds. The obvious candidate is bpf_link_type_strs[BPF_LINK_TYPE_XDP] with
>> BPF_LINK_TYPE_XDP == 6. It turns out that BPF_LINK_TYPE_XDP is missing from bpf_types.h
>> and therefore doesn't have an entry in bpf_link_type_strs:
>>
>> pos: 0
>> flags: 02000000
>> mnt_id: 13
>> link_type: (null)
>> link_id: 4
>> prog_tag: bcf7977d3b93787c
>> prog_id: 4
>> ifindex: 1
>>
>> Fixes: aa8d3a716b59 ("bpf, xdp: Add bpf_link-based XDP attachment API")
>> Signed-off-by: Lorenz Bauer <lmb@cloudflare.com>
>> ---
>
> Well, oops. Thanks for the fix!
>
> Acked-by: Andrii Nakryiko <andrii@kernel.org>
>
> It would be great to have a compilation error for something like this.
> I wonder if we can do something to detect this going forward?
>
>> include/linux/bpf_types.h | 1 +
>> 1 file changed, 1 insertion(+)
>>
>> diff --git a/include/linux/bpf_types.h b/include/linux/bpf_types.h
>> index a9db1eae6796..be95f2722ad9 100644
>> --- a/include/linux/bpf_types.h
>> +++ b/include/linux/bpf_types.h
>> @@ -135,3 +135,4 @@ BPF_LINK_TYPE(BPF_LINK_TYPE_ITER, iter)
>> #ifdef CONFIG_NET
>> BPF_LINK_TYPE(BPF_LINK_TYPE_NETNS, netns)
>> #endif
>> +BPF_LINK_TYPE(BPF_LINK_TYPE_XDP, xdp)
Lorenz, does this compile when you don't have CONFIG_NET configured? I would assume
this needs to go right below the netns one depending on CONFIG_NET.. at least the
bpf_xdp_link_lops are in net/core/dev.c which is only built under CONFIG_NET.
Thanks,
Daniel
next prev parent reply other threads:[~2021-07-16 21:01 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-16 10:04 [PATCH bpf] bpf: fix OOB read when printing XDP link fdinfo Lorenz Bauer
2021-07-16 20:43 ` Andrii Nakryiko
2021-07-16 21:00 ` Daniel Borkmann [this message]
2021-07-19 8:48 ` Lorenz Bauer
2021-07-19 8:45 ` Lorenz Bauer
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