Re: [PATCH] arm64/numa: Add more vetting in numa_set_distance()

From: John Garry
Date: Mon Oct 29 2018 - 08:14:26 EST

On 29/10/2018 11:25, Will Deacon wrote:
Hi John,

Hi Will,

On Fri, Oct 26, 2018 at 09:57:47PM +0800, John Garry wrote:
Currently it is acceptable to set the distance between 2 separate nodes to

Reject this as it is invalid.

This change avoids a crash reported in [1].


Signed-off-by: John Garry <john.garry@xxxxxxxxxx>

diff --git a/arch/arm64/mm/numa.c b/arch/arm64/mm/numa.c
index 146c04c..6092e3d 100644
--- a/arch/arm64/mm/numa.c
+++ b/arch/arm64/mm/numa.c
@@ -335,7 +335,8 @@ void __init numa_set_distance(int from, int to, int distance)

if ((u8)distance != distance ||
- (from == to && distance != LOCAL_DISTANCE)) {
+ (from == to && distance != LOCAL_DISTANCE) ||
+ (from != to && distance == LOCAL_DISTANCE)) {

The current code here is more-or-less lifted from the x86 implementation
of numa_set_distance().

Right, I did notice this. I didn't think that x86 folks would be so concerned since they generally only use ACPI, and the ACPI code already validates these distances in drivers/acpi/numa.c: slit_valid() [unlike OF code].

I think we should either factor out the sanity check
into a core helper or make the core code robust to these funny configurations.

OK, so to me it would make sense to factor out a sanity check into a core helper.



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