lkml.org 
[lkml]   [2015]   [Dec]   [9]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
From
SubjectRe: Domain faults when CONFIG_CPU_SW_DOMAIN_PAN is enabled
On Thu, Dec 03, 2015 at 09:37:51PM +0000, Peter Rosin wrote:
> I took both patches for a quick spin (a dozen boots and one hour uptime
> after that for each patch) and no incidents. I have not gathered data,
> but the crash on boot feels like it's quite a bit above 50% when there
> is a problem so this feels good (I used 5 clean reboots when I bisected
> and that worked).
>
> Reported-by: Peter Rosin <peda@axentia.se>
> Tested-by: Peter Rosin <peda@axentia.se>
>
> (and please don't forget to cc stable)

I've decided to do a more in-depth fix, so that we also solve the issue
that when we schedule in these down_read()s, we don't leak the permissive
domain register setting into the switched-to context.

Can you test this patch please? Thanks.

8<====
Subject: [PATCH] ARM: fix uaccess_with_memcpy() with SW_DOMAIN_PAN

The uaccess_with_memcpy() code is currently incompatible with the SW
PAN code: it takes locks within the region that we've changed the DACR,
potentially sleeping as a result. As we do not save and restore the
DACR across co-operative sleep events, can lead to an incorrect DACR
value later in this code path.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
---
arch/arm/include/asm/uaccess.h | 4 ++++
arch/arm/lib/uaccess_with_memcpy.c | 29 +++++++++++++++++++++++------
2 files changed, 27 insertions(+), 6 deletions(-)

diff --git a/arch/arm/include/asm/uaccess.h b/arch/arm/include/asm/uaccess.h
index 8cc85a4ebec2..35c9db857ebe 100644
--- a/arch/arm/include/asm/uaccess.h
+++ b/arch/arm/include/asm/uaccess.h
@@ -510,10 +510,14 @@ __copy_to_user_std(void __user *to, const void *from, unsigned long n);
static inline unsigned long __must_check
__copy_to_user(void __user *to, const void *from, unsigned long n)
{
+#ifndef CONFIG_UACCESS_WITH_MEMCPY
unsigned int __ua_flags = uaccess_save_and_enable();
n = arm_copy_to_user(to, from, n);
uaccess_restore(__ua_flags);
return n;
+#else
+ return arm_copy_to_user(to, from, n);
+#endif
}

extern unsigned long __must_check
diff --git a/arch/arm/lib/uaccess_with_memcpy.c b/arch/arm/lib/uaccess_with_memcpy.c
index d72b90905132..588bbc288396 100644
--- a/arch/arm/lib/uaccess_with_memcpy.c
+++ b/arch/arm/lib/uaccess_with_memcpy.c
@@ -88,6 +88,7 @@ pin_page_for_write(const void __user *_addr, pte_t **ptep, spinlock_t **ptlp)
static unsigned long noinline
__copy_to_user_memcpy(void __user *to, const void *from, unsigned long n)
{
+ unsigned long ua_flags;
int atomic;

if (unlikely(segment_eq(get_fs(), KERNEL_DS))) {
@@ -118,7 +119,9 @@ __copy_to_user_memcpy(void __user *to, const void *from, unsigned long n)
if (tocopy > n)
tocopy = n;

+ ua_flags = uaccess_save_and_enable();
memcpy((void *)to, from, tocopy);
+ uaccess_restore(ua_flags);
to += tocopy;
from += tocopy;
n -= tocopy;
@@ -145,14 +148,21 @@ arm_copy_to_user(void __user *to, const void *from, unsigned long n)
* With frame pointer disabled, tail call optimization kicks in
* as well making this test almost invisible.
*/
- if (n < 64)
- return __copy_to_user_std(to, from, n);
- return __copy_to_user_memcpy(to, from, n);
+ if (n < 64) {
+ unsigned long ua_flags = uaccess_save_and_enable();
+ n = __copy_to_user_std(to, from, n);
+ uaccess_restore(ua_flags);
+ } else {
+ n = __copy_to_user_memcpy(to, from, n);
+ }
+ return n;
}

static unsigned long noinline
__clear_user_memset(void __user *addr, unsigned long n)
{
+ unsigned long ua_flags;
+
if (unlikely(segment_eq(get_fs(), KERNEL_DS))) {
memset((void *)addr, 0, n);
return 0;
@@ -175,7 +185,9 @@ __clear_user_memset(void __user *addr, unsigned long n)
if (tocopy > n)
tocopy = n;

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

@@ -193,9 +205,14 @@ __clear_user_memset(void __user *addr, unsigned long n)
unsigned long arm_clear_user(void __user *addr, unsigned long n)
{
/* See rational for this in __copy_to_user() above. */
- if (n < 64)
- return __clear_user_std(addr, n);
- return __clear_user_memset(addr, n);
+ if (n < 64) {
+ unsigned long ua_flags = uaccess_save_and_enable();
+ n = __clear_user_std(addr, n);
+ uaccess_restore(ua_flags);
+ } else {
+ n = __clear_user_memset(addr, n);
+ }
+ return n;
}

#if 0
--
2.1.0
--
RMK's Patch system: http://www.arm.linux.org.uk/developer/patches/
FTTC broadband for 0.8mile line: currently at 9.6Mbps down 400kbps up
according to speedtest.net.


\
 
 \ /
  Last update: 2015-12-10 01:41    [W:0.066 / U:5.240 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site