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

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Date:   Fri, 31 Mar 2023 21:40:59 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Andrew Jeffery <andrew@...id.au>,
        Zev Weiss <zev@...ilderbeest.net>,
        Arnd Bergmann <arnd@...db.de>,
        Russell King <rmk+kernel@...linux.org.uk>,
        Sasha Levin <sashal@...nel.org>, linux@...linux.org.uk,
        anshuman.khandual@....com, linux-arm-kernel@...ts.infradead.org
Subject: [PATCH AUTOSEL 6.2 01/25] ARM: 9290/1: uaccess: Fix KASAN false-positives

From: Andrew Jeffery <andrew@...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@...id.au>
Signed-off-by: Zev Weiss <zev@...ilderbeest.net>
Reviewed-by: Arnd Bergmann <arnd@...db.de>
Signed-off-by: Russell King (Oracle) <rmk+kernel@...linux.org.uk>
Signed-off-by: Sasha Levin <sashal@...nel.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