linux-kernel - [PATCH v2 10/18] m68k: fix access

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Message-Id: <20220216131332.1489939-11-arnd@kernel.org>
Date:   Wed, 16 Feb 2022 14:13:24 +0100
From:   Arnd Bergmann <arnd@...nel.org>
To:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Christoph Hellwig <hch@....de>, linux-arch@...r.kernel.org,
        linux-mm@...ck.org, linux-api@...r.kernel.org, arnd@...db.de,
        linux-kernel@...r.kernel.org, viro@...iv.linux.org.uk
Cc:     linux@...linux.org.uk, will@...nel.org, guoren@...nel.org,
        bcain@...eaurora.org, geert@...ux-m68k.org, monstr@...str.eu,
        tsbogend@...ha.franken.de, nickhu@...estech.com,
        green.hu@...il.com, dinguyen@...nel.org, shorne@...il.com,
        deller@....de, mpe@...erman.id.au, peterz@...radead.org,
        mingo@...hat.com, mark.rutland@....com, hca@...ux.ibm.com,
        dalias@...c.org, davem@...emloft.net, richard@....at,
        x86@...nel.org, jcmvbkbc@...il.com, ebiederm@...ssion.com,
        akpm@...ux-foundation.org, ardb@...nel.org,
        linux-alpha@...r.kernel.org, linux-snps-arc@...ts.infradead.org,
        linux-csky@...r.kernel.org, linux-hexagon@...r.kernel.org,
        linux-ia64@...r.kernel.org, linux-m68k@...ts.linux-m68k.org,
        linux-mips@...r.kernel.org, openrisc@...ts.librecores.org,
        linux-parisc@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        linux-riscv@...ts.infradead.org, linux-s390@...r.kernel.org,
        linux-sh@...r.kernel.org, sparclinux@...r.kernel.org,
        linux-um@...ts.infradead.org, linux-xtensa@...ux-xtensa.org
Subject: [PATCH v2 10/18] m68k: fix access_ok for coldfire

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

While most m68k platforms use separate address spaces for user
and kernel space, at least coldfire does not, and the other
ones have a TASK_SIZE that is less than the entire 4GB address
range.

Using the default implementation of __access_ok() stops coldfire
user space from trivially accessing kernel memory.

Signed-off-by: Arnd Bergmann <arnd@...db.de>
---
 arch/m68k/include/asm/uaccess.h | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/arch/m68k/include/asm/uaccess.h b/arch/m68k/include/asm/uaccess.h
index 79617c0b2f91..8eb625e75452 100644
--- a/arch/m68k/include/asm/uaccess.h
+++ b/arch/m68k/include/asm/uaccess.h
@@ -12,14 +12,21 @@
 #include <asm/extable.h>
 
 /* We let the MMU do all checking */
-static inline int access_ok(const void __user *addr,
+static inline int access_ok(const void __user *ptr,
 			    unsigned long size)
 {
+	unsigned long limit = TASK_SIZE;
+	unsigned long addr = (unsigned long)ptr;
+
 	/*
 	 * XXX: for !CONFIG_CPU_HAS_ADDRESS_SPACES this really needs to check
 	 * for TASK_SIZE!
+	 * Removing this helper is probably sufficient.
 	 */
-	return 1;
+	if (IS_ENABLED(CONFIG_CPU_HAS_ADDRESS_SPACES))
+		return 1;
+
+	return (size <= limit) && (addr <= (limit - size));
 }
 
 /*
-- 
2.29.2