Patch "arm64: mm: avoid calling apply_to_page_range on empty range" has been added to the 4.4-stable tree

Patch "arm64: mm: avoid calling apply_to_page_range on empty range" has been added to the 4.4-stable tree

[gregkh]

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

    arm64: mm: avoid calling apply_to_page_range on empty range

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:
     arm64-mm-avoid-calling-apply_to_page_range-on-empty-range.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 <stable@vger.kernel.org> know about it.


>From 57adec866c0440976c96a4b8f5b59fb411b1cacb Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Mika=20Penttil=C3=A4?= <mika.penttila@nextfour.com>
Date: Tue, 26 Jan 2016 15:47:25 +0000
Subject: arm64: mm: avoid calling apply_to_page_range on empty range
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

From: Mika Penttilä <mika.penttila@nextfour.com>

commit 57adec866c0440976c96a4b8f5b59fb411b1cacb upstream.

Calling apply_to_page_range with an empty range results in a BUG_ON
from the core code. This can be triggered by trying to load the st_drv
module with CONFIG_DEBUG_SET_MODULE_RONX enabled:

  kernel BUG at mm/memory.c:1874!
  Internal error: Oops - BUG: 0 [#1] PREEMPT SMP
  Modules linked in:
  CPU: 3 PID: 1764 Comm: insmod Not tainted 4.5.0-rc1+ #2
  Hardware name: ARM Juno development board (r0) (DT)
  task: ffffffc9763b8000 ti: ffffffc975af8000 task.ti: ffffffc975af8000
  PC is at apply_to_page_range+0x2cc/0x2d0
  LR is at change_memory_common+0x80/0x108

This patch fixes the issue by making change_memory_common (called by the
set_memory_* functions) a NOP when numpages == 0, therefore avoiding the
erroneous call to apply_to_page_range and bringing us into line with x86
and s390.

Reviewed-by: Laura Abbott <labbott@redhat.com>
Acked-by: David Rientjes <rientjes@google.com>
Signed-off-by: Mika Penttilä <mika.penttila@nextfour.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 arch/arm64/mm/pageattr.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/arch/arm64/mm/pageattr.c
+++ b/arch/arm64/mm/pageattr.c
@@ -57,6 +57,9 @@ static int change_memory_common(unsigned
 	if (end < MODULES_VADDR || end >= MODULES_END)
 		return -EINVAL;
 
+	if (!numpages)
+		return 0;
+
 	data.set_mask = set_mask;
 	data.clear_mask = clear_mask;
 


Patches currently in stable-queue which might be from mika.penttila@nextfour.com are

queue-4.4/arm64-mm-avoid-calling-apply_to_page_range-on-empty-range.patch