linux-kernel - [PATCH 40/44] net: Don't pass bitfields to max

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Message-Id: <20251119224140.8616-41-david.laight.linux@gmail.com>
Date: Wed, 19 Nov 2025 22:41:36 +0000
From: david.laight.linux@...il.com
To: linux-kernel@...r.kernel.org,
	netdev@...r.kernel.org
Cc: "David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>,
	Paolo Abeni <pabeni@...hat.com>,
	David Laight <david.laight.linux@...il.com>
Subject: [PATCH 40/44] net: Don't pass bitfields to max_t()

From: David Laight <david.laight.linux@...il.com>

It is invalid to use sizeof() or typeof() in bitfields which stops
them being passed to max().
This has been fixed by using max_t().
I want to add some checks to max_t() to detect cases where the cast
discards non-zero high bits - which uses sizeof().
So add 0 to the bitfield (converting it to int) then use max().

Signed-off-by: David Laight <david.laight.linux@...il.com>
---
 include/net/tcp_ecn.h | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/include/net/tcp_ecn.h b/include/net/tcp_ecn.h
index f13e5cd2b1ac..14c00404a95f 100644
--- a/include/net/tcp_ecn.h
+++ b/include/net/tcp_ecn.h
@@ -196,7 +196,7 @@ static inline void tcp_accecn_opt_demand_min(struct sock *sk,
 	struct tcp_sock *tp = tcp_sk(sk);
 	u8 opt_demand;
 
-	opt_demand = max_t(u8, opt_demand_min, tp->accecn_opt_demand);
+	opt_demand = max(opt_demand_min, tp->accecn_opt_demand + 0);
 	tp->accecn_opt_demand = opt_demand;
 }
 
@@ -303,8 +303,7 @@ static inline void tcp_ecn_received_counters(struct sock *sk,
 			u32 bytes_mask = GENMASK_U32(31, 22);
 
 			tp->received_ecn_bytes[ecnfield - 1] += len;
-			tp->accecn_minlen = max_t(u8, tp->accecn_minlen,
-						  minlen);
+			tp->accecn_minlen = max(tp->accecn_minlen + 0, minlen);
 
 			/* Send AccECN option at least once per 2^22-byte
 			 * increase in any ECN byte counter.
-- 
2.39.5