linux-kernel - [PATCH] cb710: avoid NULL pointer subtraction

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Date:   Mon, 27 Sep 2021 14:13:57 +0200
From:   Arnd Bergmann <arnd@...nel.org>
To:     Michał Mirosław <mirq-linux@...e.qmqm.pl>,
        Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Pierre Ossman <pierre@...man.eu>
Cc:     Nathan Chancellor <nathan@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        linux-kernel@...r.kernel.org, llvm@...ts.linux.dev
Subject: [PATCH] cb710: avoid NULL pointer subtraction

From: Arnd Bergmann <arnd@...db.de>

clang-14 complains about an unusual way of converting a pointer to
an integer:

drivers/misc/cb710/sgbuf2.c:50:15: error: performing pointer subtraction with a null pointer has undefined behavior [-Werror,-Wnull-pointer-subtraction]
        return ((ptr - NULL) & 3) != 0;

Replace this with a normal cast to uintptr_t.

Fixes: 5f5bac8272be ("mmc: Driver for CB710/720 memory card reader (MMC part)")
Signed-off-by: Arnd Bergmann <arnd@...db.de>
---
 drivers/misc/cb710/sgbuf2.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/misc/cb710/sgbuf2.c b/drivers/misc/cb710/sgbuf2.c
index e5a4ed3701eb..a798fad5f03c 100644
--- a/drivers/misc/cb710/sgbuf2.c
+++ b/drivers/misc/cb710/sgbuf2.c
@@ -47,7 +47,7 @@ static inline bool needs_unaligned_copy(const void *ptr)
 #ifdef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
 	return false;
 #else
-	return ((ptr - NULL) & 3) != 0;
+	return ((uintptr_t)ptr & 3) != 0;
 #endif
 }
 
-- 
2.29.2