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Subject[PATCH 3.19.y-ckt 26/47] arm64: mm: avoid calling apply_to_page_range on empty range
Date
3.19.8-ckt15 -stable review patch.  If anyone has any objections, please let me know.

---8<------------------------------------------------------------

From: =?UTF-8?q?Mika=20Penttil=C3=A4?= <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: Kamal Mostafa <kamal@canonical.com>
---
arch/arm64/mm/pageattr.c | 3 +++
1 file changed, 3 insertions(+)

diff --git a/arch/arm64/mm/pageattr.c b/arch/arm64/mm/pageattr.c
index bb0ea94..491acbb 100644
--- a/arch/arm64/mm/pageattr.c
+++ b/arch/arm64/mm/pageattr.c
@@ -54,6 +54,9 @@ static int change_memory_common(unsigned long addr, int numpages,
if (!is_module_address(start) || !is_module_address(end - 1))
return -EINVAL;

+ if (!numpages)
+ return 0;
+
data.set_mask = set_mask;
data.clear_mask = clear_mask;

--
1.9.1
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