linux-kernel - [PATCH] net: Shrink sock.sk_err sk_err

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Date:   Sun,  3 Jul 2022 23:06:43 +0300
From:   Leonard Crestez <cdleonard@...il.com>
To:     "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>
Cc:     Paolo Abeni <pabeni@...hat.com>,
        Soheil Hassas Yeganeh <soheil@...gle.com>,
        Wei Wang <weiwan@...gle.com>,
        Joanne Koong <joannelkoong@...il.com>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH] net: Shrink sock.sk_err sk_err_soft to u16 from int

These fields hold positive errno values which are limited by
ERRNO_MAX=4095 so 16 bits is more than enough.

They are also always positive; setting them to a negative errno value
can result in falsely reporting a successful read/write of incorrect
size.

Signed-off-by: Leonard Crestez <cdleonard@...il.com>
---
 include/net/sock.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

I ran some relatively complex tests without noticing issues but some corner
case where this breaks might exist.

diff --git a/include/net/sock.h b/include/net/sock.h
index 0dd43c3df49b..acd85d1702d9 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -480,11 +480,11 @@ struct sock {
 	u16			sk_protocol;
 	u16			sk_gso_max_segs;
 	unsigned long	        sk_lingertime;
 	struct proto		*sk_prot_creator;
 	rwlock_t		sk_callback_lock;
-	int			sk_err,
+	u16			sk_err,
 				sk_err_soft;
 	u32			sk_ack_backlog;
 	u32			sk_max_ack_backlog;
 	kuid_t			sk_uid;
 	u8			sk_txrehash;
-- 
2.25.1