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 <[email protected]>
Cc: Daniel Borkmann <[email protected]>
Cc: John Fastabend <[email protected]>
Cc: Andrii Nakryiko <[email protected]>
Cc: Martin KaFai Lau <[email protected]>
Cc: Song Liu <[email protected]>
Cc: Yonghong Song <[email protected]>
Cc: KP Singh <[email protected]>
Cc: Stanislav Fomichev <[email protected]>
Cc: Hao Luo <[email protected]>
Cc: Jiri Olsa <[email protected]>
Cc: "Gustavo A. R. Silva" <[email protected]>
Cc: [email protected]
Signed-off-by: Kees Cook <[email protected]>
---
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
On Thu, Jan 5, 2023 at 11:26 AM Kees Cook <[email protected]> wrote:
>
> 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
Haven't looked closely, but these arrays should be produced somewhere
around kernel/bpf/arraymap.c (fd_array).
> -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 <[email protected]>
> Cc: Daniel Borkmann <[email protected]>
> Cc: John Fastabend <[email protected]>
> Cc: Andrii Nakryiko <[email protected]>
> Cc: Martin KaFai Lau <[email protected]>
> Cc: Song Liu <[email protected]>
> Cc: Yonghong Song <[email protected]>
> Cc: KP Singh <[email protected]>
> Cc: Stanislav Fomichev <[email protected]>
> Cc: Hao Luo <[email protected]>
> Cc: Jiri Olsa <[email protected]>
> Cc: "Gustavo A. R. Silva" <[email protected]>
> Cc: [email protected]
> Signed-off-by: Kees Cook <[email protected]>
Acked-by: Stanislav Fomichev <[email protected]>
> ---
> 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
>
Hello:
This patch was applied to bpf/bpf-next.git (master)
by Daniel Borkmann <[email protected]>:
On Thu, 5 Jan 2023 11:26:47 -0800 you wrote:
> 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);
> | ^~~~
>
> [...]
Here is the summary with links:
- bpf: Replace 0-length arrays with flexible arrays
https://git.kernel.org/bpf/bpf-next/c/129d868ede1e
You are awesome, thank you!
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