The patch titled
Subject: mm/mprotect: drop pgprot_t parameter from change_protection()
has been added to the -mm mm-unstable branch. Its filename is
mm-mprotect-drop-pgprot_t-parameter-from-change_protection.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-mprotect-drop-pgprot_t-parameter-from-change_protection.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: David Hildenbrand <david@xxxxxxxxxx>
Subject: mm/mprotect: drop pgprot_t parameter from change_protection()
Date: Fri, 23 Dec 2022 16:56:16 +0100
Being able to provide a custom protection opens the door for
inconsistencies and BUGs: for example, accidentally allowing for more
permissions than desired by other mechanisms (e.g., softdirty tracking).
vma->vm_page_prot should be the single source of truth.
Only PROT_NUMA is special: there is no way we can erroneously allow
for more permissions when removing all permissions. Special-case using
the MM_CP_PROT_NUMA flag.
Link: https://lkml.kernel.org/r/20221223155616.297723-3-david@xxxxxxxxxx
Signed-off-by: David Hildenbrand <david@xxxxxxxxxx>
Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Nadav Amit <nadav.amit@xxxxxxxxx>
Cc: Peter Xu <peterx@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
--- a/include/linux/mm.h~mm-mprotect-drop-pgprot_t-parameter-from-change_protection
+++ a/include/linux/mm.h
@@ -2134,8 +2134,7 @@ bool can_change_pte_writable(struct vm_a
pte_t pte);
extern unsigned long change_protection(struct mmu_gather *tlb,
struct vm_area_struct *vma, unsigned long start,
- unsigned long end, pgprot_t newprot,
- unsigned long cp_flags);
+ unsigned long end, unsigned long cp_flags);
extern int mprotect_fixup(struct mmu_gather *tlb, struct vm_area_struct *vma,
struct vm_area_struct **pprev, unsigned long start,
unsigned long end, unsigned long newflags);
--- a/mm/mempolicy.c~mm-mprotect-drop-pgprot_t-parameter-from-change_protection
+++ a/mm/mempolicy.c
@@ -635,8 +635,7 @@ unsigned long change_prot_numa(struct vm
tlb_gather_mmu(&tlb, vma->vm_mm);
- nr_updated = change_protection(&tlb, vma, addr, end, PAGE_NONE,
- MM_CP_PROT_NUMA);
+ nr_updated = change_protection(&tlb, vma, addr, end, MM_CP_PROT_NUMA);
if (nr_updated)
count_vm_numa_events(NUMA_PTE_UPDATES, nr_updated);
--- a/mm/mprotect.c~mm-mprotect-drop-pgprot_t-parameter-from-change_protection
+++ a/mm/mprotect.c
@@ -507,13 +507,21 @@ static unsigned long change_protection_r
unsigned long change_protection(struct mmu_gather *tlb,
struct vm_area_struct *vma, unsigned long start,
- unsigned long end, pgprot_t newprot,
- unsigned long cp_flags)
+ unsigned long end, unsigned long cp_flags)
{
+ pgprot_t newprot = vma->vm_page_prot;
unsigned long pages;
BUG_ON((cp_flags & MM_CP_UFFD_WP_ALL) == MM_CP_UFFD_WP_ALL);
+ /*
+ * Ordinary protection updates (mprotect, uffd-wp, softdirty tracking)
+ * are expected to reflect their requirements via VMA flags such that
+ * vma_set_page_prot() will adjust vma->vm_page_prot accordingly.
+ */
+ if (cp_flags & MM_CP_PROT_NUMA)
+ newprot = PAGE_NONE;
+
if (is_vm_hugetlb_page(vma))
pages = hugetlb_change_protection(vma, start, end, newprot,
cp_flags);
@@ -642,7 +650,7 @@ success:
mm_cp_flags |= MM_CP_TRY_CHANGE_WRITABLE;
vma_set_page_prot(vma);
- change_protection(tlb, vma, start, end, vma->vm_page_prot, mm_cp_flags);
+ change_protection(tlb, vma, start, end, mm_cp_flags);
/*
* Private VM_LOCKED VMA becoming writable: trigger COW to avoid major
--- a/mm/userfaultfd.c~mm-mprotect-drop-pgprot_t-parameter-from-change_protection
+++ a/mm/userfaultfd.c
@@ -730,8 +730,7 @@ void uffd_wp_range(struct mm_struct *dst
if (vma_wants_manual_pte_write_upgrade(dst_vma))
mm_cp_flags |= MM_CP_TRY_CHANGE_WRITABLE;
tlb_gather_mmu(&tlb, dst_mm);
- change_protection(&tlb, dst_vma, start, start + len, vma->vm_page_prot,
- mm_cp_flags);
+ change_protection(&tlb, dst_vma, start, start + len, mm_cp_flags);
tlb_finish_mmu(&tlb);
}
_
Patches currently in -mm which might be from david@xxxxxxxxxx are
mm-hugetlb-fix-pte-marker-handling-in-hugetlb_change_protection.patch
mm-hugetlb-fix-uffd-wp-handling-for-migration-entries-in-hugetlb_change_protection.patch
mm-userfaultfd-enable-writenotify-while-userfaultfd-wp-is-enabled-for-a-vma.patch
mm-userfaultfd-rely-on-vma-vm_page_prot-in-uffd_wp_range.patch
mm-mprotect-drop-pgprot_t-parameter-from-change_protection.patch
