| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Message-ID: <da75b2bf-0d14-6ed5-91c2-dfeba9ad55c4@iogearbox.net>
Date: Wed, 21 Feb 2024 17:39:55 +0100
From: Daniel Borkmann <daniel@...earbox.net>
To: Kees Cook <keescook@...omium.org>
Cc: Mark Rutland <mark.rutland@....com>,
"Gustavo A . R . Silva" <gustavoars@...nel.org>,
Alexei Starovoitov <ast@...nel.org>, Andrii Nakryiko <andrii@...nel.org>,
Martin KaFai Lau <martin.lau@...ux.dev>, Song Liu <song@...nel.org>,
Yonghong Song <yhs@...com>, John Fastabend <john.fastabend@...il.com>,
KP Singh <kpsingh@...nel.org>, Stanislav Fomichev <sdf@...gle.com>,
Hao Luo <haoluo@...gle.com>, Jiri Olsa <jolsa@...nel.org>,
Mykola Lysenko <mykolal@...com>, Shuah Khan <shuah@...nel.org>,
Haowen Bai <baihaowen@...zu.com>, bpf@...r.kernel.org,
linux-kselftest@...r.kernel.org, Yonghong Song <yonghong.song@...ux.dev>,
Jonathan Corbet <corbet@....net>, "David S. Miller" <davem@...emloft.net>,
Jakub Kicinski <kuba@...nel.org>, Jesper Dangaard Brouer <hawk@...nel.org>,
Joanne Koong <joannelkoong@...il.com>, Yafang Shao <laoar.shao@...il.com>,
Kui-Feng Lee <kuifeng@...a.com>, Anton Protopopov <aspsk@...valent.com>,
linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org,
netdev@...r.kernel.org, linux-hardening@...r.kernel.org
Subject: Re: [PATCH v4] bpf: Replace bpf_lpm_trie_key 0-length array with
flexible array
On 2/20/24 7:54 PM, Kees Cook wrote:
> Replace deprecated 0-length array in struct bpf_lpm_trie_key with
> flexible array. Found with GCC 13:
>
> ../kernel/bpf/lpm_trie.c:207:51: warning: array subscript i is outside array bounds of 'const __u8[0]' {aka 'const unsigned char[]'} [-Warray-bounds=]
> 207 | *(__be16 *)&key->data[i]);
> | ^~~~~~~~~~~~~
> ../include/uapi/linux/swab.h:102:54: note: in definition of macro '__swab16'
> 102 | #define __swab16(x) (__u16)__builtin_bswap16((__u16)(x))
> | ^
> ../include/linux/byteorder/generic.h:97:21: note: in expansion of macro '__be16_to_cpu'
> 97 | #define be16_to_cpu __be16_to_cpu
> | ^~~~~~~~~~~~~
> ../kernel/bpf/lpm_trie.c:206:28: note: in expansion of macro 'be16_to_cpu'
> 206 | u16 diff = be16_to_cpu(*(__be16 *)&node->data[i]
> ^
> | ^~~~~~~~~~~
> In file included from ../include/linux/bpf.h:7:
> ../include/uapi/linux/bpf.h:82:17: note: while referencing 'data'
> 82 | __u8 data[0]; /* Arbitrary size */
> | ^~~~
>
> And found at run-time under CONFIG_FORTIFY_SOURCE:
>
> UBSAN: array-index-out-of-bounds in kernel/bpf/lpm_trie.c:218:49
> index 0 is out of range for type '__u8 [*]'
>
> Changing struct bpf_lpm_trie_key is difficult since has been used by
> userspace. For example, in Cilium:
>
> struct egress_gw_policy_key {
> struct bpf_lpm_trie_key lpm_key;
> __u32 saddr;
> __u32 daddr;
> };
>
> While direct references to the "data" member haven't been found, there
> are static initializers what include the final member. For example,
> the "{}" here:
>
> struct egress_gw_policy_key in_key = {
> .lpm_key = { 32 + 24, {} },
> .saddr = CLIENT_IP,
> .daddr = EXTERNAL_SVC_IP & 0Xffffff,
> };
>
> To avoid the build time and run time warnings seen with a 0-sized
> trailing array for struct bpf_lpm_trie_key, introduce a new struct
> that correctly uses a flexible array for the trailing bytes,
> struct bpf_lpm_trie_key_u8. As part of this, include the "header"
> portion (which is just the "prefixlen" member), so it can be used
> by anything building a bpf_lpr_trie_key that has trailing members that
> aren't a u8 flexible array (like the self-test[1]), which is named
> struct bpf_lpm_trie_key_hdr.
>
> Adjust the kernel code to use struct bpf_lpm_trie_key_u8 through-out,
> and for the selftest to use struct bpf_lpm_trie_key_hdr. Add a comment
> to the UAPI header directing folks to the two new options.
>
> Link: https://lore.kernel.org/all/202206281009.4332AA33@keescook/ [1]
> Reported-by: Mark Rutland <mark.rutland@....com>
> Closes: https://paste.debian.net/hidden/ca500597/
> Acked-by: Gustavo A. R. Silva <gustavoars@...nel.org>
> Signed-off-by: Kees Cook <keescook@...omium.org>
[...]
The build in BPF CI is still broken, did you try to build selftests?
https://github.com/kernel-patches/bpf/actions/runs/7978647641
[...]
GEN-SKEL [test_progs] linked_funcs.skel.h
LINK-BPF [test_progs] test_usdt.bpf.o
GEN-SKEL [test_progs-no_alu32] profiler1.skel.h
GEN-SKEL [test_progs] test_usdt.skel.h
In file included from /tmp/work/bpf/bpf/tools/include/uapi/linux/bpf.h:11,
from test_cpp.cpp:4:
/tmp/work/bpf/bpf/tools/include/uapi/linux/bpf.h:92:17: error: ‘struct bpf_lpm_trie_key_u8::<unnamed union>::bpf_lpm_trie_key_hdr’ invalid; an anonymous union may only have public non-static data members [-fpermissive]
92 | __struct_group(bpf_lpm_trie_key_hdr, hdr, /* no attrs */,
| ^~~~~~~~~~~~~~~~~~~~
/tmp/work/bpf/bpf/tools/include/uapi/linux/stddef.h:29:10: note: in definition of macro ‘__struct_group’
29 | struct TAG { MEMBERS } ATTRS NAME; \
| ^~~
BINARY bench
make: *** [Makefile:703: /tmp/work/bpf/bpf/tools/testing/selftests/bpf/test_cpp] Error 1
make: *** Waiting for unfinished jobs....
make: Leaving directory '/tmp/work/bpf/bpf/tools/testing/selftests/bpf'
Error: Process completed with exit code 2.
> diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> index 754e68ca8744..31e9bdd4641e 100644
> --- a/include/uapi/linux/bpf.h
> +++ b/include/uapi/linux/bpf.h
> @@ -8,6 +8,7 @@
> #ifndef _UAPI__LINUX_BPF_H__
> #define _UAPI__LINUX_BPF_H__
>
> +#include <linux/stddef.h>
> #include <linux/types.h>
> #include <linux/bpf_common.h>
>
> @@ -77,12 +78,24 @@ struct bpf_insn {
> __s32 imm; /* signed immediate constant */
> };
>
> -/* Key of an a BPF_MAP_TYPE_LPM_TRIE entry */
> +/* Deprecated: use struct bpf_lpm_trie_key_u8 (when the "data" member is needed for
> + * byte access) or struct bpf_lpm_trie_key_hdr (when using an alternative type for
> + * the trailing flexible array member) instead.
> + */
> struct bpf_lpm_trie_key {
> __u32 prefixlen; /* up to 32 for AF_INET, 128 for AF_INET6 */
> __u8 data[0]; /* Arbitrary size */
> };
>
> +/* Key of an a BPF_MAP_TYPE_LPM_TRIE entry, with trailing byte array. */
> +struct bpf_lpm_trie_key_u8 {
> + __struct_group(bpf_lpm_trie_key_hdr, hdr, /* no attrs */,
> + /* up to 32 for AF_INET, 128 for AF_INET6 */
> + __u32 prefixlen;
> + );
> + __u8 data[]; /* Arbitrary size */
> +};
> +
> struct bpf_cgroup_storage_key {
> __u64 cgroup_inode_id; /* cgroup inode id */
> __u32 attach_type; /* program attach type (enum bpf_attach_type) */
Powered by blists - more mailing lists