[PATCH 5.4 065/111] drm/etnaviv: fix perfmon domain interation

From: Greg Kroah-Hartman
Date: Tue May 26 2020 - 15:23:52 EST

From: Christian Gmeiner <christian.gmeiner@xxxxxxxxx>

commit 40b697e256ccdb88aaff424b44b4d300eb8460e8 upstream.

The GC860 has one GPU device which has a 2d and 3d core. In this case
we want to expose perfmon information for both cores.

The driver has one array which contains all possible perfmon domains
with some meta data - doms_meta. Here we can see that for the GC860
two elements of that array are relevant:

doms_3d: is at index 0 in the doms_meta array with 8 perfmon domains
doms_2d: is at index 1 in the doms_meta array with 1 perfmon domain

The userspace driver wants to get a list of all perfmon domains and
their perfmon signals. This is done by iterating over all domains and
their signals. If the userspace driver wants to access the domain with
id 8 the kernel driver fails and returns invalid data from doms_3d with
and invalid offset.

This results in:
Unable to handle kernel paging request at virtual address 00000000

On such a device it is not possible to use the userspace driver at all.

The fix for this off-by-one error is quite simple.

Reported-by: Paul Cercueil <paul@xxxxxxxxxxxxxxx>
Tested-by: Paul Cercueil <paul@xxxxxxxxxxxxxxx>
Fixes: ed1dd899baa3 ("drm/etnaviv: rework perfmon query infrastructure")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Christian Gmeiner <christian.gmeiner@xxxxxxxxx>
Signed-off-by: Lucas Stach <l.stach@xxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

drivers/gpu/drm/etnaviv/etnaviv_perfmon.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/gpu/drm/etnaviv/etnaviv_perfmon.c
+++ b/drivers/gpu/drm/etnaviv/etnaviv_perfmon.c
@@ -453,7 +453,7 @@ static const struct etnaviv_pm_domain *p
if (!(gpu->identity.features & meta->feature))

- if (meta->nr_domains < (index - offset)) {
+ if (index - offset >= meta->nr_domains) {
offset += meta->nr_domains;