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Message-Id: <20230105192646.never.154-kees@kernel.org>
Date: Thu, 5 Jan 2023 11:26:47 -0800
From: Kees Cook <keescook@...omium.org>
To: Alexei Starovoitov <ast@...nel.org>
Cc: Kees Cook <keescook@...omium.org>,
Daniel Borkmann <daniel@...earbox.net>,
John Fastabend <john.fastabend@...il.com>,
Andrii Nakryiko <andrii@...nel.org>,
Martin KaFai Lau <martin.lau@...ux.dev>,
Song Liu <song@...nel.org>, Yonghong Song <yhs@...com>,
KP Singh <kpsingh@...nel.org>,
Stanislav Fomichev <sdf@...gle.com>,
Hao Luo <haoluo@...gle.com>, Jiri Olsa <jolsa@...nel.org>,
"Gustavo A. R. Silva" <gustavoars@...nel.org>, bpf@...r.kernel.org,
linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org
Subject: [PATCH] bpf: Replace 0-length arrays with flexible arrays
Zero-length arrays are deprecated[1]. Replace struct bpf_array's
union of 0-length arrays with flexible arrays. (How are the
sizes of these arrays verified?) Detected with GCC 13, using
-fstrict-flex-arrays=3:
arch/x86/net/bpf_jit_comp.c: In function 'bpf_tail_call_direct_fixup':
arch/x86/net/bpf_jit_comp.c:606:37: warning: array subscript <unknown> is outside array bounds of 'void *[0]' [-Warray-bounds=]
606 | target = array->ptrs[poke->tail_call.key];
| ~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~
In file included from include/linux/filter.h:9,
from arch/x86/net/bpf_jit_comp.c:9:
include/linux/bpf.h:1527:23: note: while referencing 'ptrs'
1527 | void *ptrs[0] __aligned(8);
| ^~~~
[1] https://www.kernel.org/doc/html/latest/process/deprecated.html#zero-length-and-one-element-arrays
Cc: Alexei Starovoitov <ast@...nel.org>
Cc: Daniel Borkmann <daniel@...earbox.net>
Cc: John Fastabend <john.fastabend@...il.com>
Cc: Andrii Nakryiko <andrii@...nel.org>
Cc: Martin KaFai Lau <martin.lau@...ux.dev>
Cc: Song Liu <song@...nel.org>
Cc: Yonghong Song <yhs@...com>
Cc: KP Singh <kpsingh@...nel.org>
Cc: Stanislav Fomichev <sdf@...gle.com>
Cc: Hao Luo <haoluo@...gle.com>
Cc: Jiri Olsa <jolsa@...nel.org>
Cc: "Gustavo A. R. Silva" <gustavoars@...nel.org>
Cc: bpf@...r.kernel.org
Signed-off-by: Kees Cook <keescook@...omium.org>
---
include/linux/bpf.h | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 3de24cfb7a3d..2131000f711e 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -1523,9 +1523,9 @@ struct bpf_array {
u32 index_mask;
struct bpf_array_aux *aux;
union {
- char value[0] __aligned(8);
- void *ptrs[0] __aligned(8);
- void __percpu *pptrs[0] __aligned(8);
+ DECLARE_FLEX_ARRAY(char, value) __aligned(8);
+ DECLARE_FLEX_ARRAY(void *, ptrs) __aligned(8);
+ DECLARE_FLEX_ARRAY(void __percpu *, pptrs) __aligned(8);
};
};
--
2.34.1
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