linux-kernel - [PATCH 4/7] wifi: cfg80211: Annotate struct cfg80211_pmsr_request with __counted

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Message-Id: <20230817211531.4193219-4-keescook@chromium.org>
Date:   Thu, 17 Aug 2023 14:15:26 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Johannes Berg <johannes@...solutions.net>
Cc:     Kees Cook <keescook@...omium.org>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        linux-wireless@...r.kernel.org, netdev@...r.kernel.org,
        Nathan Chancellor <nathan@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Tom Rix <trix@...hat.com>, linux-kernel@...r.kernel.org,
        llvm@...ts.linux.dev, linux-hardening@...r.kernel.org
Subject: [PATCH 4/7] wifi: cfg80211: Annotate struct cfg80211_pmsr_request with __counted_by

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_pmsr_request.
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@...solutions.net>
Cc: "David S. Miller" <davem@...emloft.net>
Cc: Eric Dumazet <edumazet@...gle.com>
Cc: Jakub Kicinski <kuba@...nel.org>
Cc: Paolo Abeni <pabeni@...hat.com>
Cc: linux-wireless@...r.kernel.org
Cc: netdev@...r.kernel.org
Signed-off-by: Kees Cook <keescook@...omium.org>
---
 include/net/cfg80211.h | 2 +-
 net/wireless/pmsr.c    | 3 +--
 2 files changed, 2 insertions(+), 3 deletions(-)

diff --git a/include/net/cfg80211.h b/include/net/cfg80211.h
index 5c7d091b3925..e9ca4726a732 100644
--- a/include/net/cfg80211.h
+++ b/include/net/cfg80211.h
@@ -3948,7 +3948,7 @@ struct cfg80211_pmsr_request {
 
 	struct list_head list;
 
-	struct cfg80211_pmsr_request_peer peers[];
+	struct cfg80211_pmsr_request_peer peers[] __counted_by(n_peers);
 };
 
 /**
diff --git a/net/wireless/pmsr.c b/net/wireless/pmsr.c
index 77000a264855..9611aa0bd051 100644
--- a/net/wireless/pmsr.c
+++ b/net/wireless/pmsr.c
@@ -291,6 +291,7 @@ int nl80211_pmsr_start(struct sk_buff *skb, struct genl_info *info)
 	req = kzalloc(struct_size(req, peers, count), GFP_KERNEL);
 	if (!req)
 		return -ENOMEM;
+	req->n_peers = count;
 
 	if (info->attrs[NL80211_ATTR_TIMEOUT])
 		req->timeout = nla_get_u32(info->attrs[NL80211_ATTR_TIMEOUT]);
@@ -321,8 +322,6 @@ int nl80211_pmsr_start(struct sk_buff *skb, struct genl_info *info)
 			goto out_err;
 		idx++;
 	}
-
-	req->n_peers = count;
 	req->cookie = cfg80211_assign_cookie(rdev);
 	req->nl_portid = info->snd_portid;
 
-- 
2.34.1