The patch titled
Subject: userfaultfd: fix PTE unmapping stack-allocated PTE copies
has been added to the -mm mm-hotfixes-unstable branch. Its filename is
userfaultfd-fix-pte-unmapping-stack-allocated-pte-copies.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/userfaultfd-fix-pte-unmapping-stack-allocated-pte-copies.patch
This patch will later appear in the mm-hotfixes-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Suren Baghdasaryan <surenb@xxxxxxxxxx>
Subject: userfaultfd: fix PTE unmapping stack-allocated PTE copies
Date: Wed, 26 Feb 2025 10:55:09 -0800
Current implementation of move_pages_pte() copies source and destination
PTEs in order to detect concurrent changes to PTEs involved in the move.
However these copies are also used to unmap the PTEs, which will fail if
CONFIG_HIGHPTE is enabled because the copies are allocated on the stack.
Fix this by using the actual PTEs which were kmap()ed.
Link: https://lkml.kernel.org/r/20250226185510.2732648-3-surenb@xxxxxxxxxx
Fixes: adef440691ba ("userfaultfd: UFFDIO_MOVE uABI")
Signed-off-by: Suren Baghdasaryan <surenb@xxxxxxxxxx>
Reported-by: Peter Xu <peterx@xxxxxxxxxx>
Reviewed-by: Peter Xu <peterx@xxxxxxxxxx>
Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Cc: Barry Song <21cnbao@xxxxxxxxx>
Cc: Barry Song <v-songbaohua@xxxxxxxx>
Cc: David Hildenbrand <david@xxxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Jann Horn <jannh@xxxxxxxxxx>
Cc: Kalesh Singh <kaleshsingh@xxxxxxxxxx>
Cc: Liam R. Howlett <Liam.Howlett@xxxxxxxxxx>
Cc: Lokesh Gidra <lokeshgidra@xxxxxxxxxx>
Cc: Lorenzo Stoakes <lorenzo.stoakes@xxxxxxxxxx>
Cc: Matthew Wilcow (Oracle) <willy@xxxxxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/userfaultfd.c | 20 ++++++++++----------
1 file changed, 10 insertions(+), 10 deletions(-)
--- a/mm/userfaultfd.c~userfaultfd-fix-pte-unmapping-stack-allocated-pte-copies
+++ a/mm/userfaultfd.c
@@ -1290,8 +1290,8 @@ retry:
spin_unlock(src_ptl);
if (!locked) {
- pte_unmap(&orig_src_pte);
- pte_unmap(&orig_dst_pte);
+ pte_unmap(src_pte);
+ pte_unmap(dst_pte);
src_pte = dst_pte = NULL;
/* now we can block and wait */
folio_lock(src_folio);
@@ -1307,8 +1307,8 @@ retry:
/* at this point we have src_folio locked */
if (folio_test_large(src_folio)) {
/* split_folio() can block */
- pte_unmap(&orig_src_pte);
- pte_unmap(&orig_dst_pte);
+ pte_unmap(src_pte);
+ pte_unmap(dst_pte);
src_pte = dst_pte = NULL;
err = split_folio(src_folio);
if (err)
@@ -1333,8 +1333,8 @@ retry:
goto out;
}
if (!anon_vma_trylock_write(src_anon_vma)) {
- pte_unmap(&orig_src_pte);
- pte_unmap(&orig_dst_pte);
+ pte_unmap(src_pte);
+ pte_unmap(dst_pte);
src_pte = dst_pte = NULL;
/* now we can block and wait */
anon_vma_lock_write(src_anon_vma);
@@ -1352,8 +1352,8 @@ retry:
entry = pte_to_swp_entry(orig_src_pte);
if (non_swap_entry(entry)) {
if (is_migration_entry(entry)) {
- pte_unmap(&orig_src_pte);
- pte_unmap(&orig_dst_pte);
+ pte_unmap(src_pte);
+ pte_unmap(dst_pte);
src_pte = dst_pte = NULL;
migration_entry_wait(mm, src_pmd, src_addr);
err = -EAGAIN;
@@ -1396,8 +1396,8 @@ retry:
src_folio = folio;
src_folio_pte = orig_src_pte;
if (!folio_trylock(src_folio)) {
- pte_unmap(&orig_src_pte);
- pte_unmap(&orig_dst_pte);
+ pte_unmap(src_pte);
+ pte_unmap(dst_pte);
src_pte = dst_pte = NULL;
/* now we can block and wait */
folio_lock(src_folio);
_
Patches currently in -mm which might be from surenb@xxxxxxxxxx are
userfaultfd-do-not-block-on-locking-a-large-folio-with-raised-refcount.patch
userfaultfd-fix-pte-unmapping-stack-allocated-pte-copies.patch
mm-avoid-extra-mem_alloc_profiling_enabled-checks.patch
alloc_tag-uninline-code-gated-by-mem_alloc_profiling_key-in-slab-allocator.patch
alloc_tag-uninline-code-gated-by-mem_alloc_profiling_key-in-page-allocator.patch
mm-introduce-vma_start_read_locked_nested-helpers.patch
mm-move-per-vma-lock-into-vm_area_struct.patch
mm-mark-vma-as-detached-until-its-added-into-vma-tree.patch
mm-introduce-vma_iter_store_attached-to-use-with-attached-vmas.patch
mm-mark-vmas-detached-upon-exit.patch
types-move-struct-rcuwait-into-typesh.patch
mm-allow-vma_start_read_locked-vma_start_read_locked_nested-to-fail.patch
mm-move-mmap_init_lock-out-of-the-header-file.patch
mm-uninline-the-main-body-of-vma_start_write.patch
refcount-provide-ops-for-cases-when-objects-memory-can-be-reused.patch
refcount-provide-ops-for-cases-when-objects-memory-can-be-reused-fix.patch
refcount-introduce-__refcount_addinc_not_zero_limited_acquire.patch
mm-replace-vm_lock-and-detached-flag-with-a-reference-count.patch
mm-replace-vm_lock-and-detached-flag-with-a-reference-count-fix.patch
mm-move-lesser-used-vma_area_struct-members-into-the-last-cacheline.patch
mm-debug-print-vm_refcnt-state-when-dumping-the-vma.patch
mm-remove-extra-vma_numab_state_init-call.patch
mm-prepare-lock_vma_under_rcu-for-vma-reuse-possibility.patch
mm-make-vma-cache-slab_typesafe_by_rcu.patch
mm-make-vma-cache-slab_typesafe_by_rcu-fix.patch
docs-mm-document-latest-changes-to-vm_lock.patch
