From: John Fastabend <john.fastabend@gmail.com>
To: Lorenz Bauer <lmb@cloudflare.com>,
Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
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>
Cc: kernel-team@cloudflare.com, Lorenz Bauer <lmb@cloudflare.com>,
Andrii Nakryiko <andriin@fb.com>,
netdev@vger.kernel.org, bpf@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: RE: [PATCH bpf v2 1/1] bpf: fix OOB read when printing XDP link fdinfo
Date: Mon, 19 Jul 2021 16:11:43 -0700 [thread overview]
Message-ID: <60f606afc66a1_1e832208e7@john-XPS-13-9370.notmuch> (raw)
In-Reply-To: <20210719085134.43325-2-lmb@cloudflare.com>
Lorenz Bauer 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>
> ---
> 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..ae3ac3a2018c 100644
> --- a/include/linux/bpf_types.h
> +++ b/include/linux/bpf_types.h
> @@ -134,4 +134,5 @@ BPF_LINK_TYPE(BPF_LINK_TYPE_CGROUP, cgroup)
> BPF_LINK_TYPE(BPF_LINK_TYPE_ITER, iter)
> #ifdef CONFIG_NET
> BPF_LINK_TYPE(BPF_LINK_TYPE_NETNS, netns)
> +BPF_LINK_TYPE(BPF_LINK_TYPE_XDP, xdp)
> #endif
> --
> 2.30.2
>
Still lgtm.
Acked-by; John Fastabend <john.fastabend@gmail.com>
next prev parent reply other threads:[~2021-07-20 0:13 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-19 8:51 [PATCH bpf v2 0/1] bpf: fix OOB read when printing XDP link fdinfo Lorenz Bauer
2021-07-19 8:51 ` [PATCH bpf v2 1/1] " Lorenz Bauer
2021-07-19 23:11 ` John Fastabend [this message]
2021-07-19 22:31 ` [PATCH bpf v2 0/1] " Andrii Nakryiko
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