From: David Hildenbrand <david@redhat.com>
Date: Fri, 13 Jun 2025 09:27:00 +0000 (+0200)
Subject: mm/huge_memory: don't ignore queried cachemode in vmf_insert_pfn_pud()
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=09fefdca80aebd1023e827cb0ee174983d829d18;p=thirdparty%2Flinux.git

mm/huge_memory: don't ignore queried cachemode in vmf_insert_pfn_pud()

Patch series "mm/huge_memory: vmf_insert_folio_*() and
vmf_insert_pfn_pud() fixes", v3.

While working on improving vm_normal_page() and friends, I stumbled over
this issues: refcounted "normal" folios must not be marked using
pmd_special() / pud_special().  Otherwise, we're effectively telling the
system that these folios are no "normal", violating the rules we
documented for vm_normal_page().

Fortunately, there are not many pmd_special()/pud_special() users yet.  So
far there doesn't seem to be serious damage.

Tested using the ndctl tests ("ndctl:dax" suite).


This patch (of 3):

We set up the cache mode but ...  don't forward the updated pgprot to
insert_pfn_pud().

Only a problem on x86-64 PAT when mapping PFNs using PUDs that require a
special cachemode.

Fix it by using the proper pgprot where the cachemode was setup.

It is unclear in which configurations we would get the cachemode wrong:
through vfio seems possible.  Getting cachemodes wrong is usually ...
bad.  As the fix is easy, let's backport it to stable.

Identified by code inspection.

Link: https://lkml.kernel.org/r/20250613092702.1943533-1-david@redhat.com
Link: https://lkml.kernel.org/r/20250613092702.1943533-2-david@redhat.com
Fixes: 7b806d229ef1 ("mm: remove vmf_insert_pfn_xxx_prot() for huge page-table entries")
Signed-off-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Dan Williams <dan.j.williams@intel.com>
Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Tested-by: Dan Williams <dan.j.williams@intel.com>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Dev Jain <dev.jain@arm.com>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Mariano Pache <npache@redhat.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Zi Yan <ziy@nvidia.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index d3e66136e41a3..49b98082c5401 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1516,10 +1516,9 @@ static pud_t maybe_pud_mkwrite(pud_t pud, struct vm_area_struct *vma)
 }
 
 static void insert_pfn_pud(struct vm_area_struct *vma, unsigned long addr,
-		pud_t *pud, pfn_t pfn, bool write)
+		pud_t *pud, pfn_t pfn, pgprot_t prot, bool write)
 {
 	struct mm_struct *mm = vma->vm_mm;
-	pgprot_t prot = vma->vm_page_prot;
 	pud_t entry;
 
 	if (!pud_none(*pud)) {
@@ -1581,7 +1580,7 @@ vm_fault_t vmf_insert_pfn_pud(struct vm_fault *vmf, pfn_t pfn, bool write)
 	pfnmap_setup_cachemode_pfn(pfn_t_to_pfn(pfn), &pgprot);
 
 	ptl = pud_lock(vma->vm_mm, vmf->pud);
-	insert_pfn_pud(vma, addr, vmf->pud, pfn, write);
+	insert_pfn_pud(vma, addr, vmf->pud, pfn, pgprot, write);
 	spin_unlock(ptl);
 
 	return VM_FAULT_NOPAGE;
@@ -1625,7 +1624,7 @@ vm_fault_t vmf_insert_folio_pud(struct vm_fault *vmf, struct folio *folio,
 		add_mm_counter(mm, mm_counter_file(folio), HPAGE_PUD_NR);
 	}
 	insert_pfn_pud(vma, addr, vmf->pud, pfn_to_pfn_t(folio_pfn(folio)),
-		write);
+		       vma->vm_page_prot, write);
 	spin_unlock(ptl);
 
 	return VM_FAULT_NOPAGE;