On Thu, Jan 5, 2023 at 11:26 AM Kees Cook <keescook@xxxxxxxxxxxx> 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 <ast@xxxxxxxxxx> > Cc: Daniel Borkmann <daniel@xxxxxxxxxxxxx> > Cc: John Fastabend <john.fastabend@xxxxxxxxx> > Cc: Andrii Nakryiko <andrii@xxxxxxxxxx> > Cc: Martin KaFai Lau <martin.lau@xxxxxxxxx> > Cc: Song Liu <song@xxxxxxxxxx> > Cc: Yonghong Song <yhs@xxxxxx> > Cc: KP Singh <kpsingh@xxxxxxxxxx> > Cc: Stanislav Fomichev <sdf@xxxxxxxxxx> > Cc: Hao Luo <haoluo@xxxxxxxxxx> > Cc: Jiri Olsa <jolsa@xxxxxxxxxx> > Cc: "Gustavo A. R. Silva" <gustavoars@xxxxxxxxxx> > Cc: bpf@xxxxxxxxxxxxxxx > Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx> Acked-by: Stanislav Fomichev <sdf@xxxxxxxxxx> > --- > 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 >
