Re: [PATCH bpf v1 1/1] bpf: Fix sk_local_storage diag dumping uninitialized special fields

[Mykyta Yatsenko <mykyta.yatsenko5@gmail.com>]

On 4/23/26 11:23 PM, Amery Hung wrote:
> Call check_and_init_map_value() after the copy_map_value() to zero out
> special field regions. diag_get() copies sk_local_storage map values
> into a netlink message using copy_map_value{_locked}(), which
> intentionally skip special fields. However, the destination buffer from
> nla_reserve_64bit() is not zeroed and the skipped regions contain
> uninitialized skb data can be sent to userspace.
> 
> Fixes: 1ed4d92458a9 ("bpf: INET_DIAG support in bpf_sk_storage")
> Signed-off-by: Amery Hung <ameryhung@gmail.com>
> ---
>   net/core/bpf_sk_storage.c | 1 +
>   1 file changed, 1 insertion(+)
> 
> diff --git a/net/core/bpf_sk_storage.c b/net/core/bpf_sk_storage.c
> index 14eb7812bda4..b50d26a542ed 100644
> --- a/net/core/bpf_sk_storage.c
> +++ b/net/core/bpf_sk_storage.c
> @@ -558,6 +558,7 @@ static int diag_get(struct bpf_local_storage_data *sdata, struct sk_buff *skb)
>   				      sdata->data, true);
>   	else
>   		copy_map_value(&smap->map, nla_data(nla_value), sdata->data);
> +	check_and_init_map_value(&smap->map, nla_data(nla_value));
>   

I think check_and_init_map_value() should be moved before the
copy_map_value(), because copy_map_value_locked() already uses
spin lock special field, which if uninitialized can deadlock?

>   	nla_nest_end(skb, nla_stg);
>   	return 0;