@@ -5141,12 +5141,12 @@ const struct vm_operations_struct hugetlb_vm_ops = {
};
static pte_t make_huge_pte(struct vm_area_struct *vma, struct page *page,
- int writable)
+ bool try_mkwrite)
{
pte_t entry;
unsigned int shift = huge_page_shift(hstate_vma(vma));
- if (writable) {
+ if (try_mkwrite && (vma->vm_flags & VM_WRITE)) {
entry = huge_pte_mkwrite(huge_pte_mkdirty(mk_huge_pte(page,
vma->vm_page_prot)));
} else {
@@ -5199,7 +5199,7 @@ static void
hugetlb_install_folio(struct vm_area_struct *vma, pte_t *ptep, unsigned long addr,
struct folio *new_folio, pte_t old, unsigned long sz)
{
- pte_t newpte = make_huge_pte(vma, &new_folio->page, 1);
+ pte_t newpte = make_huge_pte(vma, &new_folio->page, true);
__folio_mark_uptodate(new_folio);
hugetlb_add_new_anon_rmap(new_folio, vma, addr);
@@ -6223,8 +6223,7 @@ static vm_fault_t hugetlb_no_page(struct address_space *mapping,
hugetlb_add_new_anon_rmap(folio, vma, vmf->address);
else
hugetlb_add_file_rmap(folio);
- new_pte = make_huge_pte(vma, &folio->page, ((vma->vm_flags & VM_WRITE)
- && (vma->vm_flags & VM_SHARED)));
+ new_pte = make_huge_pte(vma, &folio->page, vma->vm_flags & VM_SHARED);
/*
* If this pte was previously wr-protected, keep it wr-protected even
* if populated.
@@ -6556,7 +6555,6 @@ int hugetlb_mfill_atomic_pte(pte_t *dst_pte,
spinlock_t *ptl;
int ret = -ENOMEM;
struct folio *folio;
- int writable;
bool folio_in_pagecache = false;
if (uffd_flags_mode_is(flags, MFILL_ATOMIC_POISON)) {
@@ -6710,12 +6708,8 @@ int hugetlb_mfill_atomic_pte(pte_t *dst_pte,
* For either: (1) CONTINUE on a non-shared VMA, or (2) UFFDIO_COPY
* with wp flag set, don't set pte write bit.
*/
- if (wp_enabled || (is_continue && !vm_shared))
- writable = 0;
- else
- writable = dst_vma->vm_flags & VM_WRITE;
-
- _dst_pte = make_huge_pte(dst_vma, &folio->page, writable);
+ _dst_pte = make_huge_pte(dst_vma, &folio->page,
+ !wp_enabled && !(is_continue && !vm_shared));
/*
* Always mark UFFDIO_COPY page dirty; note that this may not be
* extremely important for hugetlbfs for now since swapping is not
If we have to trigger a hugetlb folio copy during fork() because the anon folio might be pinned, we currently unconditionally create a writable PTE. However, the VMA might not have write permissions (VM_WRITE) at that point. Fix it by checking the VMA for VM_WRITE. Make the code less error prone by moving checking for VM_WRITE into make_huge_pte(), and letting callers only specify whether we should try making it writable. A simple reproducer that longter-pins the folios using liburing to then mprotect(PROT_READ) the folios befor fork() [1] results in: Before: [FAIL] access should not have worked After: [PASS] access did not work as expected [1] https://gitlab.com/davidhildenbrand/scratchspace/-/raw/main/reproducers/hugetlb-mkwrite-fork.c This is rather a corner case, so stable might not be warranted. Fixes: 4eae4efa2c29 ("hugetlb: do early cow when page pinned on src mm") Cc: Muchun Song <muchun.song@linux.dev> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Peter Xu <peterx@redhat.com> Cc: Guillaume Morin <guillaume@morinfr.org> Signed-off-by: David Hildenbrand <david@redhat.com> --- mm/hugetlb.c | 18 ++++++------------ 1 file changed, 6 insertions(+), 12 deletions(-)