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SubjectRe: [PATCH 5/7] wifi: cfg80211: Annotate struct cfg80211_rnr_elems with __counted_by
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On 8/17/23 15:15, Kees Cook wrote:
> Prepare for the coming implementation by GCC and Clang of the __counted_by
> attribute. Flexible array members annotated with __counted_by can have
> their accesses bounds-checked at run-time checking via CONFIG_UBSAN_BOUNDS
> (for array indexing) and CONFIG_FORTIFY_SOURCE (for strcpy/memcpy-family
> functions).
>
> As found with Coccinelle[1], add __counted_by for struct cfg80211_rnr_elems.
> Additionally, since the element count member must be set before accessing
> the annotated flexible array member, move its initialization earlier.
>
> [1] https://github.com/kees/kernel-tools/blob/trunk/coccinelle/examples/counted_by.cocci
>
> Cc: Johannes Berg <johannes@sipsolutions.net>
> Cc: "David S. Miller" <davem@davemloft.net>
> Cc: Eric Dumazet <edumazet@google.com>
> Cc: Jakub Kicinski <kuba@kernel.org>
> Cc: Paolo Abeni <pabeni@redhat.com>
> Cc: linux-wireless@vger.kernel.org
> Cc: netdev@vger.kernel.org
> Signed-off-by: Kees Cook <keescook@chromium.org>

Reviewed-by: Gustavo A. R. Silva <gustavoars@kernel.org>

Thanks
--
Gustavo

> ---
> include/net/cfg80211.h | 2 +-
> net/wireless/nl80211.c | 2 +-
> 2 files changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/include/net/cfg80211.h b/include/net/cfg80211.h
> index e9ca4726a732..6efe216c01d2 100644
> --- a/include/net/cfg80211.h
> +++ b/include/net/cfg80211.h
> @@ -1204,7 +1204,7 @@ struct cfg80211_rnr_elems {
> struct {
> const u8 *data;
> size_t len;
> - } elem[];
> + } elem[] __counted_by(cnt);
> };
>
> /**
> diff --git a/net/wireless/nl80211.c b/net/wireless/nl80211.c
> index 9ba4266368db..0ffebf1a1eb6 100644
> --- a/net/wireless/nl80211.c
> +++ b/net/wireless/nl80211.c
> @@ -5470,13 +5470,13 @@ nl80211_parse_rnr_elems(struct wiphy *wiphy, struct nlattr *attrs,
> elems = kzalloc(struct_size(elems, elem, num_elems), GFP_KERNEL);
> if (!elems)
> return ERR_PTR(-ENOMEM);
> + elems->cnt = num_elems;
>
> nla_for_each_nested(nl_elems, attrs, rem_elems) {
> elems->elem[i].data = nla_data(nl_elems);
> elems->elem[i].len = nla_len(nl_elems);
> i++;
> }
> - elems->cnt = num_elems;
> return elems;
> }
>

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