[PATCH] drm/panthor: Check VMA boundaries for PMD mappings

[Christian A. Ehrhardt]

When checking a different patch[1] sashiko AI pointed out that
panthor needs the same fix[2]:

In the ->huge_fault handler do not install a PMD huge page
mapping if the huge page exceeds the boundaries of the VMA.

[1] https://lore.kernel.org/lkml/20260622215718.1532689-1-lk@xxxxxxx/
[2] https://sashiko.dev/#/patchset/20260622215718.1532689-1-lk%40c--e.de

Cc: Boris Brezillon <boris.brezillon@xxxxxxxxxxxxx>
Cc: Steven Price <steven.price@xxxxxxx>
Cc: Liviu Dudau <liviu.dudau@xxxxxxx>
Fixes: 68cbf96b1e9b ("drm/panthor: Part ways with drm_gem_shmem_object")
Signed-off-by: Christian A. Ehrhardt <lk@xxxxxxx>
---
 drivers/gpu/drm/panthor/panthor_gem.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

NOTE:
The panthor version is only compile tested because I don't
have the hardware. However, the code is identical to that
fixed in [1] and I have a reproducer for that.

No need for for stable backports. The code is new in 7.1.

diff --git a/drivers/gpu/drm/panthor/panthor_gem.c b/drivers/gpu/drm/panthor/panthor_gem.c
index a1e2eb1ca7bb..54535bae2b0c 100644
--- a/drivers/gpu/drm/panthor/panthor_gem.c
+++ b/drivers/gpu/drm/panthor/panthor_gem.c
@@ -802,9 +802,13 @@ static vm_fault_t insert_page(struct vm_fault *vmf, unsigned int order, struct p
 	} else if (order == PMD_ORDER) {
 		unsigned long pfn = page_to_pfn(page);
 		unsigned long paddr = pfn << PAGE_SHIFT;
+		struct vm_area_struct *vma = vmf->vma;
+		unsigned long start = ALIGN_DOWN(vmf->address, PMD_SIZE);
+		unsigned long end = start + PMD_SIZE;
+		bool in_range = vma->vm_start <= start && end <= vma->vm_end;
 		bool aligned = (vmf->address & ~PMD_MASK) == (paddr & ~PMD_MASK);
 
-		if (aligned &&
+		if (aligned && in_range &&
 		    folio_test_pmd_mappable(page_folio(page))) {
 			pfn &= PMD_MASK >> PAGE_SHIFT;
 			return vmf_insert_pfn_pmd(vmf, pfn, vmf->flags & FAULT_FLAG_WRITE);
-- 
2.43.0