netdev - Re: [PATCH v2 bpf-next] libbpf: fix false uninitialized variable warning

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

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <87imhhv1av.fsf@cloudflare.com>
Date:   Thu, 30 Apr 2020 10:13:28 +0200
From:   Jakub Sitnicki <jakub@...udflare.com>
To:     Andrii Nakryiko <andriin@...com>
Cc:     bpf@...r.kernel.org, netdev@...r.kernel.org, ast@...com,
        daniel@...earbox.net, andrii.nakryiko@...il.com, kernel-team@...com
Subject: Re: [PATCH v2 bpf-next] libbpf: fix false uninitialized variable warning

On Thu, Apr 30, 2020 at 04:14 AM CEST, Andrii Nakryiko wrote:
> Some versions of GCC falsely detect that vi might not be initialized. That's
> not true, but let's silence it with NULL initialization.
>
> Signed-off-by: Andrii Nakryiko <andriin@...com>
> ---
>  tools/lib/bpf/libbpf.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
> index d86ff8214b96..977add1b73e2 100644
> --- a/tools/lib/bpf/libbpf.c
> +++ b/tools/lib/bpf/libbpf.c
> @@ -5003,8 +5003,8 @@ static int bpf_object__collect_map_relos(struct bpf_object *obj,
>  					 GElf_Shdr *shdr, Elf_Data *data)
>  {
>  	int i, j, nrels, new_sz, ptr_sz = sizeof(void *);
> +	const struct btf_var_secinfo *vi = NULL;
>  	const struct btf_type *sec, *var, *def;
> -	const struct btf_var_secinfo *vi;
>  	const struct btf_member *member;
>  	struct bpf_map *map, *targ_map;
>  	const char *name, *mname;

Alternatively we could borrow the kernel uninitialized_var macro:

include/linux/compiler-clang.h:#define uninitialized_var(x) x = *(&(x))
include/linux/compiler-gcc.h:#define uninitialized_var(x) x = x