From: Mika Penttilä <mika.penttila@nextfour.com>
Date: Tue, 26 Jan 2016 15:47:25 +0000 (+0000)
Subject: UPSTREAM: arm64: mm: avoid calling apply_to_page_range on empty range
X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=644210f3f890d1e5481378d28d150d1c5f4191fa;p=GitHub%2Fexynos8895%2Fandroid_kernel_samsung_universal8895.git

UPSTREAM: arm64: mm: avoid calling apply_to_page_range on empty range

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.

Cc: <stable@vger.kernel.org>
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>

Bug: 30369029
Patchset: kaslr-arm64-4.4

(cherry picked from commit 57adec866c0440976c96a4b8f5b59fb411b1cacb)
Signed-off-by: Jeff Vander Stoep <jeffv@google.com>
Change-Id: Ia107d3b324cc8237f669778a7c9c3abae8637501
---

diff --git a/arch/arm64/mm/pageattr.c b/arch/arm64/mm/pageattr.c
index 29ee7d85ca4c..0795c3a36d8f 100644
--- a/arch/arm64/mm/pageattr.c
+++ b/arch/arm64/mm/pageattr.c
@@ -72,6 +72,9 @@ static int change_memory_common(unsigned long addr, int numpages,
 	    !(area->flags & VM_ALLOC))
 		return -EINVAL;
 
+	if (!numpages)
+		return 0;
+
 	data.set_mask = set_mask;
 	data.clear_mask = clear_mask;