[PATCH 5.16 36/37] m68k: fix access_ok for coldfire

Greg Kroah-Hartman
2022-03-25T15:34:21Z

From: Arnd Bergmann <arnd@arndb.de>

commit 26509034bef198525d5936c116cbd0c3fa491c0b upstream.

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.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Cc: stable@vger.kernel.org
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
arch/m68k/include/asm/uaccess.h | 15 +++++++++------
1 file changed, 9 insertions(+), 6 deletions(-)

--- a/arch/m68k/include/asm/uaccess.h
+++ b/arch/m68k/include/asm/uaccess.h
@@ -12,14 +12,17 @@
#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)
{
- /*
- * XXX: for !CONFIG_CPU_HAS_ADDRESS_SPACES this really needs to check
- * for TASK_SIZE!
- */
- return 1;
+ unsigned long limit = TASK_SIZE;
+ unsigned long addr = (unsigned long)ptr;
+
+ if (IS_ENABLED(CONFIG_CPU_HAS_ADDRESS_SPACES) ||
+ !IS_ENABLED(CONFIG_MMU))
+ return 1;
+
+ return (size <= limit) && (addr <= (limit - size));
}

/*