[merged mm-stable] mm-add-vm_uffd_rwp-vma-flag.patch removed from -mm tree
Andrew Morton <[email protected]> Tue, 04 Aug 2026 19:23:42 -0700
| Newsgroups | org.kernel.vger.mm-commits |
|---|---|
| Message-ID | <[email protected]> |
The quilt patch titled
Subject: mm: add VM_UFFD_RWP VMA flag
has been removed from the -mm tree. Its filename was
mm-add-vm_uffd_rwp-vma-flag.patch
This patch was dropped because it was merged into the mm-stable branch
of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
------------------------------------------------------
From: "Kiryl Shutsemau (Meta)" <[email protected]>
Subject: mm: add VM_UFFD_RWP VMA flag
Date: Wed, 8 Jul 2026 12:14:06 +0100
Preparatory patch for userfaultfd read-write protection (RWP). RWP
extends userfaultfd protection from plain write-protection (WP) to full
read-write protection: accesses to an RWP-protected range -- reads as well
as writes -- trap through userfaultfd.
Reserve VM_UFFD_RWP, add the userfaultfd_rwp() and userfaultfd_protected()
helpers, and wire up the smaps "ur" entry and the trace-flag table the
rest of the series will use. The flag is gated on CONFIG_USERFAULTFD_RWP,
which is introduced together with the UAPI in a later patch; until then
VM_UFFD_RWP aliases VM_NONE and every downstream check folds to dead code.
Nothing sets or queries the flag yet.
Link: https://lore.kernel.org/[email protected]
Signed-off-by: Kiryl Shutsemau <[email protected]>
Assisted-by: Claude:claude-opus-4-6
Reviewed-by: Mike Rapoport (Microsoft) <[email protected]>
Reviewed-by: SeongJae Park <[email protected]>
Reviewed-by: Lorenzo Stoakes <[email protected]>
Cc: Andrea Arcangeli <[email protected]>
Cc: David Hildenbrand <[email protected]>
Cc: James Houghton <[email protected]>
Cc: Jonathan Corbet <[email protected]>
Cc: Liam Howlett <[email protected]>
Cc: Paolo Bonzini <[email protected]>
Cc: Peter Xu <[email protected]>
Cc: Sean Christopherson <[email protected]>
Cc: Suren Baghdasaryan <[email protected]>
Cc: Vlastimil Babka <[email protected]>
Cc: Zi Yan <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
---
Documentation/filesystems/proc.rst | 1
fs/proc/task_mmu.c | 3 +
include/linux/mm.h | 41 ++++++++++++++++--------
include/linux/userfaultfd_k.h | 45 +++++++++++++++++++++------
include/trace/events/mmflags.h | 7 ++++
5 files changed, 74 insertions(+), 23 deletions(-)
--- a/Documentation/filesystems/proc.rst~mm-add-vm_uffd_rwp-vma-flag
+++ a/Documentation/filesystems/proc.rst
@@ -608,6 +608,7 @@ encoded manner. The codes are the follow
um userfaultfd missing tracking
uw userfaultfd wr-protect tracking
ui userfaultfd minor fault
+ ur userfaultfd read-write-protect tracking
ss shadow/guarded control stack page
sl sealed
lf lock on fault pages
--- a/fs/proc/task_mmu.c~mm-add-vm_uffd_rwp-vma-flag
+++ a/fs/proc/task_mmu.c
@@ -1237,6 +1237,9 @@ static void show_smap_vma_flags(struct s
#ifdef CONFIG_HAVE_ARCH_USERFAULTFD_MINOR
[ilog2(VM_UFFD_MINOR)] = "ui",
#endif /* CONFIG_HAVE_ARCH_USERFAULTFD_MINOR */
+#ifdef CONFIG_USERFAULTFD_RWP
+ [ilog2(VM_UFFD_RWP)] = "ur",
+#endif
#ifdef CONFIG_ARCH_HAS_USER_SHADOW_STACK
[ilog2(VM_SHADOW_STACK)] = "ss",
#endif
--- a/include/linux/mm.h~mm-add-vm_uffd_rwp-vma-flag
+++ a/include/linux/mm.h
@@ -354,6 +354,7 @@ enum {
#endif
DECLARE_VMA_BIT(UFFD_MINOR, 41),
DECLARE_VMA_BIT(SEALED, 42),
+ DECLARE_VMA_BIT(UFFD_RWP, 43),
/* Flags that reuse flags above. */
DECLARE_VMA_BIT_ALIAS(PKEY_BIT0, HIGH_ARCH_0),
DECLARE_VMA_BIT_ALIAS(PKEY_BIT1, HIGH_ARCH_1),
@@ -497,12 +498,17 @@ enum {
#else
#define VM_UFFD_MINOR VM_NONE
#endif
+#ifdef CONFIG_USERFAULTFD_RWP
+#define VM_UFFD_RWP INIT_VM_FLAG(UFFD_RWP)
+#else
+#define VM_UFFD_RWP VM_NONE
+#endif
/*
- * vma_flags_t masks for the userfaultfd VMA flags. VMA_UFFD_MINOR is gated on
- * the same config as VM_UFFD_MINOR -- which implies 64BIT, where the bit fits
- * -- so an out-of-range bit is never fed to mk_vma_flags() on a build whose
- * bitmap cannot hold it.
+ * vma_flags_t masks for the userfaultfd VMA flags. The two high-bit modes are
+ * gated on the same configs as their VM_* flags above -- both of which imply
+ * 64BIT -- so an out-of-range bit is never fed to mk_vma_flags() on a build
+ * whose bitmap cannot hold it.
*/
#define VMA_UFFD_MISSING mk_vma_flags(VMA_UFFD_MISSING_BIT)
#define VMA_UFFD_WP mk_vma_flags(VMA_UFFD_WP_BIT)
@@ -511,6 +517,11 @@ enum {
#else
#define VMA_UFFD_MINOR EMPTY_VMA_FLAGS
#endif
+#ifdef CONFIG_USERFAULTFD_RWP
+#define VMA_UFFD_RWP mk_vma_flags(VMA_UFFD_RWP_BIT)
+#else
+#define VMA_UFFD_RWP EMPTY_VMA_FLAGS
+#endif
#ifdef CONFIG_64BIT
#define VM_ALLOW_ANY_UNCACHED INIT_VM_FLAG(ALLOW_ANY_UNCACHED)
@@ -649,22 +660,24 @@ enum {
* reconsistuted upon page fault, so necessitate page table copying upon fork.
*
* Note that these flags should be compared with the DESTINATION VMA not the
- * source, as VM_UFFD_WP may not be propagated to destination, while all other
- * flags will be.
+ * source: VM_UFFD_WP and VM_UFFD_RWP may be cleared on the destination
+ * (dup_userfaultfd() -> userfaultfd_reset_ctx() when the parent context did
+ * not negotiate UFFD_FEATURE_EVENT_FORK), while all other flags propagate.
*
* VM_PFNMAP / VM_MIXEDMAP - These contain kernel-mapped data which cannot be
* reasonably reconstructed on page fault.
*
* VM_UFFD_WP - Encodes metadata about an installed uffd
- * write protect handler, which cannot be
- * reconstructed on page fault.
+ * VM_UFFD_RWP write- or read-write-protect handler, which
+ * cannot be reconstructed on page fault.
*
- * We always copy pgtables when dst_vma has uffd-wp
- * enabled even if it's file-backed
- * (e.g. shmem). Because when uffd-wp is enabled,
- * pgtable contains uffd-wp protection information,
- * that's something we can't retrieve from page cache,
- * and skip copying will lose those info.
+ * We always copy pgtables when dst_vma has the
+ * uffd PTE bit in use even if it's file-backed
+ * (e.g. shmem). Because when the uffd bit is
+ * in use, the pgtable contains the protection
+ * information, that's something we can't
+ * retrieve from page cache, and skip copying
+ * will lose those info.
*
* VM_MAYBE_GUARD - Could contain page guard region markers which
* by design are a property of the page tables
--- a/include/linux/userfaultfd_k.h~mm-add-vm_uffd_rwp-vma-flag
+++ a/include/linux/userfaultfd_k.h
@@ -21,10 +21,11 @@
#include <linux/hugetlb_inline.h>
/* The set of all possible UFFD-related VM flags. */
-#define __VM_UFFD_FLAGS (VM_UFFD_MISSING | VM_UFFD_WP | VM_UFFD_MINOR)
+#define __VM_UFFD_FLAGS (VM_UFFD_MISSING | VM_UFFD_MINOR | \
+ VM_UFFD_WP | VM_UFFD_RWP)
#define __VMA_UFFD_FLAGS mk_vma_flags_from_masks(VMA_UFFD_MISSING, VMA_UFFD_WP, \
- VMA_UFFD_MINOR)
+ VMA_UFFD_MINOR, VMA_UFFD_RWP)
/*
* CAREFUL: Check include/uapi/asm-generic/fcntl.h when defining
@@ -168,7 +169,8 @@ static inline bool is_mergeable_vm_userf
/*
* Never enable huge pmd sharing on some uffd registered vmas:
*
- * - VM_UFFD_WP VMAs, because write protect information is per pgtable entry.
+ * - VM_UFFD_WP and VM_UFFD_RWP VMAs, because the write protect / access
+ * tracking information is per pgtable entry.
*
* - VM_UFFD_MINOR VMAs, because otherwise we would never get minor faults for
* VMAs which share huge pmds. (If you have two mappings to the same
@@ -179,20 +181,25 @@ static inline bool is_mergeable_vm_userf
static inline bool uffd_disable_huge_pmd_share(struct vm_area_struct *vma)
{
return vma_test_any_mask(vma,
- mk_vma_flags_from_masks(VMA_UFFD_WP, VMA_UFFD_MINOR));
+ mk_vma_flags_from_masks(VMA_UFFD_WP, VMA_UFFD_RWP,
+ VMA_UFFD_MINOR));
}
/*
- * Don't do fault around for either WP or MINOR registered uffd range. For
+ * Don't do fault around for WP, RWP or MINOR registered uffd range. For
* MINOR registered range, fault around will be a total disaster and ptes can
* be installed without notifications; for WP it should mostly be fine as long
* as the fault around checks for pte_none() before the installation, however
- * to be super safe we just forbid it.
+ * to be super safe we just forbid it; for RWP, pre-faulted neighbours would
+ * be indistinguishable from accessed pages in PAGEMAP_SCAN (PAGE_IS_ACCESSED)
+ * and pollute the tracked working set, so each page must be populated by its
+ * own fault.
*/
static inline bool uffd_disable_fault_around(struct vm_area_struct *vma)
{
return vma_test_any_mask(vma,
- mk_vma_flags_from_masks(VMA_UFFD_WP, VMA_UFFD_MINOR));
+ mk_vma_flags_from_masks(VMA_UFFD_WP, VMA_UFFD_RWP,
+ VMA_UFFD_MINOR));
}
static inline bool userfaultfd_missing(struct vm_area_struct *vma)
@@ -210,6 +217,16 @@ static inline bool userfaultfd_minor(str
return vma_test_any_mask(vma, VMA_UFFD_MINOR);
}
+static inline bool userfaultfd_rwp(struct vm_area_struct *vma)
+{
+ return vma_test_single_mask(vma, VMA_UFFD_RWP);
+}
+
+static inline bool userfaultfd_protected(struct vm_area_struct *vma)
+{
+ return userfaultfd_wp(vma) || userfaultfd_rwp(vma);
+}
+
static inline bool userfaultfd_pte_wp(struct vm_area_struct *vma,
pte_t pte)
{
@@ -330,6 +347,16 @@ static inline bool userfaultfd_minor(str
return false;
}
+static inline bool userfaultfd_rwp(struct vm_area_struct *vma)
+{
+ return false;
+}
+
+static inline bool userfaultfd_protected(struct vm_area_struct *vma)
+{
+ return false;
+}
+
static inline bool userfaultfd_pte_wp(struct vm_area_struct *vma,
pte_t pte)
{
@@ -423,8 +450,8 @@ static inline bool userfaultfd_wp_use_ma
}
/*
- * Returns true if this is a swap pte and was uffd-wp wr-protected in either
- * forms (pte marker or a normal swap pte), false otherwise.
+ * Returns true if this swap pte carries uffd-tracked state in either
+ * form (pte marker or a normal swap pte), false otherwise.
*/
static inline bool pte_swp_uffd_any(pte_t pte)
{
--- a/include/trace/events/mmflags.h~mm-add-vm_uffd_rwp-vma-flag
+++ a/include/trace/events/mmflags.h
@@ -186,6 +186,12 @@ IF_HAVE_PG_ARCH_3(arch_3)
# define IF_HAVE_UFFD_MINOR(flag, name)
#endif
+#ifdef CONFIG_USERFAULTFD_RWP
+# define IF_HAVE_UFFD_RWP(flag, name) {flag, name},
+#else
+# define IF_HAVE_UFFD_RWP(flag, name)
+#endif
+
#if defined(CONFIG_64BIT) || defined(CONFIG_PPC32)
# define IF_HAVE_VM_DROPPABLE(flag, name) {flag, name},
#else
@@ -207,6 +213,7 @@ IF_HAVE_UFFD_MINOR(VM_UFFD_MINOR, "uffd_
{VM_PFNMAP, "pfnmap" }, \
{VM_MAYBE_GUARD, "maybe_guard" }, \
{VM_UFFD_WP, "uffd_wp" }, \
+IF_HAVE_UFFD_RWP(VM_UFFD_RWP, "uffd_rwp" ) \
{VM_LOCKED, "locked" }, \
{VM_IO, "io" }, \
{VM_SEQ_READ, "seqread" }, \
_
Patches currently in -mm which might be from [email protected] are
selftests-mm-add-pagemap_scan-test-for-thp-pmd-holes.patch
mm-huge_memory-remove-unused-can_split_folio.patch
mm-huge_memory-fold-split_folio_to_list_to_order-into-split_folio_to_order.patch
mm-fold-userfaultfd_rwp-to-false-without-config_arch_has_pte_protnone.patch