[PATCH AUTOSEL 6.2 01/25] ARM: 9290/1: uaccess: Fix KASAN false-positives

Sasha Levin
2023-04-01T01:41:40Z

From: Andrew Jeffery <andrew@aj.id.au>

[ Upstream commit ceac10c83b330680cc01ceaaab86cd49f4f30d81 ]

__copy_to_user_memcpy() and __clear_user_memset() had been calling
memcpy() and memset() respectively, leading to false-positive KASAN
reports when starting userspace:

[ 10.707901] Run /init as init process
[ 10.731892] process '/bin/busybox' started with executable stack
[ 10.745234] ==================================================================
[ 10.745796] BUG: KASAN: user-memory-access in __clear_user_memset+0x258/0x3ac
[ 10.747260] Write of size 2687 at addr 000de581 by task init/1

Use __memcpy() and __memset() instead to allow userspace access, which
is of course the intent of these functions.

Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
Signed-off-by: Zev Weiss <zev@bewilderbeest.net>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
arch/arm/lib/uaccess_with_memcpy.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/arm/lib/uaccess_with_memcpy.c b/arch/arm/lib/uaccess_with_memcpy.c
index 14eecaaf295fa..e4c2677cc1e9e 100644
--- a/arch/arm/lib/uaccess_with_memcpy.c
+++ b/arch/arm/lib/uaccess_with_memcpy.c
@@ -116,7 +116,7 @@ __copy_to_user_memcpy(void __user *to, const void *from, unsigned long n)
tocopy = n;

ua_flags = uaccess_save_and_enable();
- memcpy((void *)to, from, tocopy);
+ __memcpy((void *)to, from, tocopy);
uaccess_restore(ua_flags);
to += tocopy;
from += tocopy;
@@ -178,7 +178,7 @@ __clear_user_memset(void __user *addr, unsigned long n)
tocopy = n;

ua_flags = uaccess_save_and_enable();
- memset((void *)addr, 0, tocopy);
+ __memset((void *)addr, 0, tocopy);
uaccess_restore(ua_flags);
addr += tocopy;
n -= tocopy;
--
2.39.2