linux-hardening - [PATCH 6/7] wifi: cfg80211: Annotate struct cfg80211_scan_request with __counted

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Date:   Thu, 17 Aug 2023 14:15:28 -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 6/7] wifi: cfg80211: Annotate struct cfg80211_scan_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_scan_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 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/net/cfg80211.h b/include/net/cfg80211.h
index 6efe216c01d2..a2afc94a5408 100644
--- a/include/net/cfg80211.h
+++ b/include/net/cfg80211.h
@@ -2544,7 +2544,7 @@ struct cfg80211_scan_request {
 	struct cfg80211_scan_6ghz_params *scan_6ghz_params;
 
 	/* keep last */
-	struct ieee80211_channel *channels[];
+	struct ieee80211_channel *channels[] __counted_by(n_channels);
 };
 
 static inline void get_random_mask_addr(u8 *buf, const u8 *addr, const u8 *mask)
-- 
2.34.1