Patch "ARM: 8613/1: Fix the uaccess crash on PB11MPCore" has been added to the 4.4-stable tree

This is a note to let you know that I've just added the patch titled

ARM: 8613/1: Fix the uaccess crash on PB11MPCore

to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:

     arm-8613-1-fix-the-uaccess-crash-on-pb11mpcore.patch

and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Linus Walleij <[email protected]>
Date: Tue, 13 Sep 2016 12:31:17 +0100
Subject: ARM: 8613/1: Fix the uaccess crash on PB11MPCore

From: Linus Walleij <[email protected]>

commit 90f92c631b210c1e97080b53a9d863783281a932 upstream.

The following patch was sketched by Russell in response to my crashes on the PB11MPCore after the patch for software-based priviledged no access support for ARMv8.1. See this thread:
http://marc.info/?l=linux-arm-kernel&m=144051749807214&w=2

I am unsure what is going on, I suspect everyone involved in the discussion is. I just want to repost this to get the discussion restarted, as I still have to apply this patch with every kernel iteration to get my PB11MPCore Realview running.

Testing by Neil Armstrong on the Oxnas NAS has revealed that this bug exist also on that widely deployed hardware, so we are probably currently regressing all ARM11MPCore systems.

---
 arch/arm/kernel/smp_tlb.c |    7 +++++++
 1 file changed, 7 insertions(+)

@@ -9,6 +9,7 @@
  */
 #include <linux/preempt.h>
 #include <linux/smp.h>
+#include <linux/uaccess.h>
 
 #include <asm/smp_plat.h>
 #include <asm/tlbflush.h>

@@ -40,8 +41,11 @@ static inline void ipi_flush_tlb_mm(void
 static inline void ipi_flush_tlb_page(void *arg)
 {
 	struct tlb_args *ta = (struct tlb_args *)arg;
+	unsigned int __ua_flags = uaccess_save_and_enable();
 
 	local_flush_tlb_page(ta->ta_vma, ta->ta_start);
+
+	uaccess_restore(__ua_flags);
 }
 
 static inline void ipi_flush_tlb_kernel_page(void *arg)

@@ -54,8 +58,11 @@ static inline void ipi_flush_tlb_kernel_
 static inline void ipi_flush_tlb_range(void *arg)
 {
 	struct tlb_args *ta = (struct tlb_args *)arg;
+	unsigned int __ua_flags = uaccess_save_and_enable();
 
 	local_flush_tlb_range(ta->ta_vma, ta->ta_start, ta->ta_end);
+
+	uaccess_restore(__ua_flags);
 }
 
 static inline void ipi_flush_tlb_kernel_range(void *arg)

Patches currently in stable-queue which might be from [email protected] are

queue-4.4/arm-ux500-fix-prcmu_is_cpu_in_wfi-calculation.patch queue-4.4/arm-8634-1-hw_breakpoint-blacklist-scorpion-cpus.patch queue-4.4/arm-8613-1-fix-the-uaccess-crash-on-pb11mpcore.patch