[PATCH] drm/xe/userptr: properly setup pfn_flags_mask

[Matthew Auld <matthew.auld@intel.com>]

Currently we just leave it uninitialised, which at first looks harmless,
however we also don't zero out the pfn array, and with pfn_flags_mask
the idea is to be able set individual flags for a given range of pfn or
completely ignore them, outside of default_flags. So here we end up with
pfn[i] & pfn_flags_mask, and if both are uninitialised we might get back
an unexpected flags value, like asking for read only with default_flags,
but getting back write on top, leading to potentially bogus behaviour.

To fix this ensure we zero the pfn_flags_mask, such that hmm only
considers the default_flags and not also the initial pfn[i] value.

Fixes: 81e058a3e7fd ("drm/xe: Introduce helper to populate userptr")
Signed-off-by: Matthew Auld <matthew.auld@intel.com>
Cc: Matthew Brost <matthew.brost@intel.com>
Cc: Thomas Hellström <thomas.hellstrom@intel.com>
Cc: <stable@vger.kernel.org> # v6.10+
---
 drivers/gpu/drm/xe/xe_hmm.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/gpu/drm/xe/xe_hmm.c b/drivers/gpu/drm/xe/xe_hmm.c
index 089834467880..8c3cd65fa4b3 100644
--- a/drivers/gpu/drm/xe/xe_hmm.c
+++ b/drivers/gpu/drm/xe/xe_hmm.c
@@ -206,6 +206,7 @@ int xe_hmm_userptr_populate_range(struct xe_userptr_vma *uvma,
 		goto free_pfns;
 	}
 
+	hmm_range.pfn_flags_mask = 0;
 	hmm_range.default_flags = flags;
 	hmm_range.hmm_pfns = pfns;
 	hmm_range.notifier = &userptr->notifier;
-- 
2.48.1