linux/arch/um/kernel/maccess.c
Richard Weinberger f75b1b1bed um: Implement probe_kernel_read()
UML needs it's own probe_kernel_read() to handle kernel
mode faults correctly.
The implementation uses mincore() on the host side to detect
whether a page is owned by the UML kernel process.

This fixes also a possible crash when sysrq-t is used.
Starting with 3.10 sysrq-t calls probe_kernel_read() to
read details from the kernel workers. As kernel worker are
completely async pointers may turn NULL while reading them.

Cc: <stian@nixia.no>
Cc: <tj@kernel.org>
Cc: <stable@vger.kernel.org> # 3.10.x
Signed-off-by: Richard Weinberger <richard@nod.at>
2013-09-07 10:38:34 +02:00

25 lines
638 B
C

/*
* Copyright (C) 2013 Richard Weinberger <richrd@nod.at>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*/
#include <linux/uaccess.h>
#include <linux/kernel.h>
#include <os.h>
long probe_kernel_read(void *dst, const void *src, size_t size)
{
void *psrc = (void *)rounddown((unsigned long)src, PAGE_SIZE);
if ((unsigned long)src < PAGE_SIZE || size <= 0)
return -EFAULT;
if (os_mincore(psrc, size + src - psrc) <= 0)
return -EFAULT;
return __probe_kernel_read(dst, src, size);
}