netdev - [PATCH 2/4] net: make sockptr_is

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Message-Id: <20200728163836.562074-3-hch@lst.de>
Date:   Tue, 28 Jul 2020 18:38:34 +0200
From:   Christoph Hellwig <hch@....de>
To:     "David S. Miller" <davem@...emloft.net>
Cc:     Jan Engelhardt <jengelh@...i.de>, Ido Schimmel <idosch@...sch.org>,
        "Jason A. Donenfeld" <Jason@...c4.com>,
        David Laight <David.Laight@...LAB.COM>, netdev@...r.kernel.org
Subject: [PATCH 2/4] net: make sockptr_is_null strict aliasing safe

While the kernel in general is not strict aliasing safe we can trivially
do that in sockptr_is_null without affecting code generation, so always
check the actually assigned union member.

Reported-by: Jan Engelhardt <jengelh@...i.de>
Signed-off-by: Christoph Hellwig <hch@....de>
---
 include/linux/sockptr.h | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/include/linux/sockptr.h b/include/linux/sockptr.h
index 7d5cdb2b30b5f0..b13ea1422f93a5 100644
--- a/include/linux/sockptr.h
+++ b/include/linux/sockptr.h
@@ -64,7 +64,9 @@ static inline int __must_check init_user_sockptr(sockptr_t *sp, void __user *p)
 
 static inline bool sockptr_is_null(sockptr_t sockptr)
 {
-	return !sockptr.user && !sockptr.kernel;
+	if (sockptr_is_kernel(sockptr))
+		return !sockptr.kernel;
+	return !sockptr.user;
 }
 
 static inline int copy_from_sockptr(void *dst, sockptr_t src, size_t size)
-- 
2.27.0