linux-kernel - [PATCH AUTOSEL 5.4 2/6] MIPS: BCM47XX: Cast memcmp() of function to (void *)

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Message-Id: <20221009205423.1203538-2-sashal@kernel.org>
Date:   Sun,  9 Oct 2022 16:54:18 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Kees Cook <keescook@...omium.org>,
        Hauke Mehrtens <hauke@...ke-m.de>,
        Rafał Miłecki <zajec5@...il.com>,
        Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        linux-mips@...r.kernel.org, Nathan Chancellor <nathan@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        llvm@...ts.linux.dev, kernel test robot <lkp@...el.com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH AUTOSEL 5.4 2/6] MIPS: BCM47XX: Cast memcmp() of function to (void *)

From: Kees Cook <keescook@...omium.org>

[ Upstream commit 0dedcf6e3301836eb70cfa649052e7ce4fcd13ba ]

Clang is especially sensitive about argument type matching when using
__overloaded functions (like memcmp(), etc). Help it see that function
pointers are just "void *". Avoids this error:

arch/mips/bcm47xx/prom.c:89:8: error: no matching function for call to 'memcmp'
                   if (!memcmp(prom_init, prom_init + mem, 32))
                        ^~~~~~
include/linux/string.h:156:12: note: candidate function not viable: no known conversion from 'void (void)' to 'const void *' for 1st argument extern int memcmp(const void *,const void *,__kernel_size_t);

Cc: Hauke Mehrtens <hauke@...ke-m.de>
Cc: "Rafał Miłecki" <zajec5@...il.com>
Cc: Thomas Bogendoerfer <tsbogend@...ha.franken.de>
Cc: linux-mips@...r.kernel.org
Cc: Nathan Chancellor <nathan@...nel.org>
Cc: Nick Desaulniers <ndesaulniers@...gle.com>
Cc: llvm@...ts.linux.dev
Reported-by: kernel test robot <lkp@...el.com>
Link: https://lore.kernel.org/lkml/202209080652.sz2d68e5-lkp@intel.com
Signed-off-by: Kees Cook <keescook@...omium.org>
Signed-off-by: Thomas Bogendoerfer <tsbogend@...ha.franken.de>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 arch/mips/bcm47xx/prom.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/mips/bcm47xx/prom.c b/arch/mips/bcm47xx/prom.c
index 135a5407f015..d26d9a6f6ee7 100644
--- a/arch/mips/bcm47xx/prom.c
+++ b/arch/mips/bcm47xx/prom.c
@@ -85,7 +85,7 @@ static __init void prom_init_mem(void)
 			pr_debug("Assume 128MB RAM\n");
 			break;
 		}
-		if (!memcmp(prom_init, prom_init + mem, 32))
+		if (!memcmp((void *)prom_init, (void *)prom_init + mem, 32))
 			break;
 	}
 	lowmem = mem;
@@ -162,7 +162,7 @@ void __init bcm47xx_prom_highmem_init(void)
 
 	off = EXTVBASE + __pa(off);
 	for (extmem = 128 << 20; extmem < 512 << 20; extmem <<= 1) {
-		if (!memcmp(prom_init, (void *)(off + extmem), 16))
+		if (!memcmp((void *)prom_init, (void *)(off + extmem), 16))
 			break;
 	}
 	extmem -= lowmem;
-- 
2.35.1