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

[Christian A. Ehrhardt]

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

All other ->huge_fault handlers have similar checks and the
resulting mapping will trigger a VM_BUG_ON_VMA() if it ever
reaches copy_pmd_range().

Cc: Pedro Demarchi Gomes <pedrodemargomes@xxxxxxxxx>
Cc: Boris Brezillon <boris.brezillon@xxxxxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Fixes: fc3bbf34e643 ("drm/shmem-helper: Fix huge page mapping in fault handler")
Signed-off-by: Christian A. Ehrhardt <lk@xxxxxxx>
---
 drivers/gpu/drm/drm_gem_shmem_helper.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c b/drivers/gpu/drm/drm_gem_shmem_helper.c
index c989459eb215..00807039f8d7 100644
--- a/drivers/gpu/drm/drm_gem_shmem_helper.c
+++ b/drivers/gpu/drm/drm_gem_shmem_helper.c
@@ -597,9 +597,13 @@ static vm_fault_t try_insert_pfn(struct vm_fault *vmf, unsigned int order,
 #ifdef CONFIG_ARCH_SUPPORTS_PMD_PFNMAP
 	} else if (order == PMD_ORDER) {
 		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(pfn_to_page(pfn)))) {
 			vm_fault_t ret;
 
-- 
2.43.0