The quilt patch titled
Subject: mm/shmem: restore SHMEM_HUGE_DENY precedence over MADV_COLLAPSE
has been removed from the -mm tree. Its filename was
mm-shmem-restore-shmem_huge_deny-precedence-over-madv_collapse.patch
This patch was dropped because it was merged into the mm-hotfixes-stable branch
of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
------------------------------------------------------
From: "Zach O'Keefe" <zokeefe(a)google.com>
Subject: mm/shmem: restore SHMEM_HUGE_DENY precedence over MADV_COLLAPSE
Date: Sat, 24 Dec 2022 00:20:35 -0800
SHMEM_HUGE_DENY is for emergency use by the admin, to disable allocation
of shmem huge pages if, for example, a dangerous bug is found in their
usage: see "deny" in Documentation/mm/transhuge.rst. An app using
madvise(,,MADV_COLLAPSE) should not be allowed to override it: restore its
precedence over shmem_huge_force.
Restore SHMEM_HUGE_DENY precedence over MADV_COLLAPSE.
Link: https://lkml.kernel.org/r/20221224082035.3197140-2-zokeefe@google.com
Fixes: 7c6c6cc4d3a2 ("mm/shmem: add flag to enforce shmem THP in hugepage_vma_check()")
Signed-off-by: Zach O'Keefe <zokeefe(a)google.com>
Suggested-by: Hugh Dickins <hughd(a)google.com>
Acked-by: David Hildenbrand <david(a)redhat.com>
Cc: Yang Shi <shy828301(a)gmail.com>
Cc: <stable(a)vger.kernel.org>
Signed-off-by: Andrew Morton <akpm(a)linux-foundation.org>
---
mm/shmem.c | 6 ++----
1 file changed, 2 insertions(+), 4 deletions(-)
--- a/mm/shmem.c~mm-shmem-restore-shmem_huge_deny-precedence-over-madv_collapse
+++ a/mm/shmem.c
@@ -478,12 +478,10 @@ bool shmem_is_huge(struct vm_area_struct
if (vma && ((vma->vm_flags & VM_NOHUGEPAGE) ||
test_bit(MMF_DISABLE_THP, &vma->vm_mm->flags)))
return false;
- if (shmem_huge_force)
- return true;
- if (shmem_huge == SHMEM_HUGE_FORCE)
- return true;
if (shmem_huge == SHMEM_HUGE_DENY)
return false;
+ if (shmem_huge_force || shmem_huge == SHMEM_HUGE_FORCE)
+ return true;
switch (SHMEM_SB(inode->i_sb)->huge) {
case SHMEM_HUGE_ALWAYS:
_
Patches currently in -mm which might be from zokeefe(a)google.com are
The quilt patch titled
Subject: mm/MADV_COLLAPSE: don't expand collapse when vm_end is past requested end
has been removed from the -mm tree. Its filename was
mm-madv_collapse-dont-expand-collapse-when-vm_end-is-past-requested-end.patch
This patch was dropped because it was merged into the mm-hotfixes-stable branch
of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
------------------------------------------------------
From: "Zach O'Keefe" <zokeefe(a)google.com>
Subject: mm/MADV_COLLAPSE: don't expand collapse when vm_end is past requested end
Date: Sat, 24 Dec 2022 00:20:34 -0800
MADV_COLLAPSE acts on one hugepage-aligned/sized region at a time, until
it has collapsed all eligible memory contained within the bounds supplied
by the user.
At the top of each hugepage iteration we (re)lock mmap_lock and
(re)validate the VMA for eligibility and update variables that might have
changed while mmap_lock was dropped. One thing that might occur is that
the VMA could be resized, and as such, we refetch vma->vm_end to make sure
we don't collapse past the end of the VMA's new end.
However, it's possible that when refetching vma->vm_end that we expand the
region acted on by MADV_COLLAPSE if vma->vm_end is greater than size+len
supplied by the user.
The consequence here is that we may attempt to collapse more memory than
requested, possibly yielding either "too much success" or "false failure"
user-visible results. An example of the former is if we MADV_COLLAPSE the
first 4MiB of a 2TiB mmap()'d file, the incorrect refetch would cause the
operation to block for much longer than anticipated as we attempt to
collapse the entire TiB region. An example of the latter is that applying
MADV_COLLPSE to a 4MiB file mapped to the start of a 6MiB VMA will
successfully collapse the first 4MiB, then incorrectly attempt to collapse
the last hugepage-aligned/sized region -- fail (since readahead/page cache
lookup will fail) -- and report a failure to the user.
I don't believe there is a kernel stability concern here as we always
(re)validate the VMA / region accordingly. Also as Hugh mentions, the
user-visible effects are: we try to collapse more memory than requested
by the user, and/or failing an operation that should have otherwise
succeeded. An example is trying to collapse a 4MiB file contained
within a 12MiB VMA.
Don't expand the acted-on region when refetching vma->vm_end.
Link: https://lkml.kernel.org/r/20221224082035.3197140-1-zokeefe@google.com
Fixes: 4d24de9425f7 ("mm: MADV_COLLAPSE: refetch vm_end after reacquiring mmap_lock")
Signed-off-by: Zach O'Keefe <zokeefe(a)google.com>
Reported-by: Hugh Dickins <hughd(a)google.com>
Cc: Yang Shi <shy828301(a)gmail.com>
Cc: <stable(a)vger.kernel.org>
Signed-off-by: Andrew Morton <akpm(a)linux-foundation.org>
---
mm/khugepaged.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/mm/khugepaged.c~mm-madv_collapse-dont-expand-collapse-when-vm_end-is-past-requested-end
+++ a/mm/khugepaged.c
@@ -2647,7 +2647,7 @@ int madvise_collapse(struct vm_area_stru
goto out_nolock;
}
- hend = vma->vm_end & HPAGE_PMD_MASK;
+ hend = min(hend, vma->vm_end & HPAGE_PMD_MASK);
}
mmap_assert_locked(mm);
memset(cc->node_load, 0, sizeof(cc->node_load));
_
Patches currently in -mm which might be from zokeefe(a)google.com are
The quilt patch titled
Subject: mm/userfaultfd: enable writenotify while userfaultfd-wp is enabled for a VMA
has been removed from the -mm tree. Its filename was
mm-userfaultfd-enable-writenotify-while-userfaultfd-wp-is-enabled-for-a-vma.patch
This patch was dropped because it was merged into the mm-hotfixes-stable branch
of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
------------------------------------------------------
From: David Hildenbrand <david(a)redhat.com>
Subject: mm/userfaultfd: enable writenotify while userfaultfd-wp is enabled for a VMA
Date: Fri, 9 Dec 2022 09:09:12 +0100
Currently, we don't enable writenotify when enabling userfaultfd-wp on a
shared writable mapping (for now only shmem and hugetlb). The consequence
is that vma->vm_page_prot will still include write permissions, to be set
as default for all PTEs that get remapped (e.g., mprotect(), NUMA hinting,
page migration, ...).
So far, vma->vm_page_prot is assumed to be a safe default, meaning that we
only add permissions (e.g., mkwrite) but not remove permissions (e.g.,
wrprotect). For example, when enabling softdirty tracking, we enable
writenotify. With uffd-wp on shared mappings, that changed. More details
on vma->vm_page_prot semantics were summarized in [1].
This is problematic for uffd-wp: we'd have to manually check for a uffd-wp
PTEs/PMDs and manually write-protect PTEs/PMDs, which is error prone.
Prone to such issues is any code that uses vma->vm_page_prot to set PTE
permissions: primarily pte_modify() and mk_pte().
Instead, let's enable writenotify such that PTEs/PMDs/... will be mapped
write-protected as default and we will only allow selected PTEs that are
definitely safe to be mapped without write-protection (see
can_change_pte_writable()) to be writable. In the future, we might want
to enable write-bit recovery -- e.g., can_change_pte_writable() -- at more
locations, for example, also when removing uffd-wp protection.
This fixes two known cases:
(a) remove_migration_pte() mapping uffd-wp'ed PTEs writable, resulting
in uffd-wp not triggering on write access.
(b) do_numa_page() / do_huge_pmd_numa_page() mapping uffd-wp'ed PTEs/PMDs
writable, resulting in uffd-wp not triggering on write access.
Note that do_numa_page() / do_huge_pmd_numa_page() can be reached even
without NUMA hinting (which currently doesn't seem to be applicable to
shmem), for example, by using uffd-wp with a PROT_WRITE shmem VMA. On
such a VMA, userfaultfd-wp is currently non-functional.
Note that when enabling userfaultfd-wp, there is no need to walk page
tables to enforce the new default protection for the PTEs: we know that
they cannot be uffd-wp'ed yet, because that can only happen after enabling
uffd-wp for the VMA in general.
Also note that this makes mprotect() on ranges with uffd-wp'ed PTEs not
accidentally set the write bit -- which would result in uffd-wp not
triggering on later write access. This commit makes uffd-wp on shmem
behave just like uffd-wp on anonymous memory in that regard, even though,
mixing mprotect with uffd-wp is controversial.
[1] https://lkml.kernel.org/r/92173bad-caa3-6b43-9d1e-9a471fdbc184@redhat.com
Link: https://lkml.kernel.org/r/20221209080912.7968-1-david@redhat.com
Fixes: b1f9e876862d ("mm/uffd: enable write protection for shmem & hugetlbfs")
Signed-off-by: David Hildenbrand <david(a)redhat.com>
Reported-by: Ives van Hoorne <ives(a)codesandbox.io>
Debugged-by: Peter Xu <peterx(a)redhat.com>
Acked-by: Peter Xu <peterx(a)redhat.com>
Cc: Hugh Dickins <hughd(a)google.com>
Cc: Alistair Popple <apopple(a)nvidia.com>
Cc: Mike Rapoport <rppt(a)linux.vnet.ibm.com>
Cc: Nadav Amit <nadav.amit(a)gmail.com>
Cc: Andrea Arcangeli <aarcange(a)redhat.com>
Cc: <stable(a)vger.kernel.org>
Signed-off-by: Andrew Morton <akpm(a)linux-foundation.org>
---
fs/userfaultfd.c | 28 ++++++++++++++++++++++------
mm/mmap.c | 4 ++++
2 files changed, 26 insertions(+), 6 deletions(-)
--- a/fs/userfaultfd.c~mm-userfaultfd-enable-writenotify-while-userfaultfd-wp-is-enabled-for-a-vma
+++ a/fs/userfaultfd.c
@@ -108,6 +108,21 @@ static bool userfaultfd_is_initialized(s
return ctx->features & UFFD_FEATURE_INITIALIZED;
}
+static void userfaultfd_set_vm_flags(struct vm_area_struct *vma,
+ vm_flags_t flags)
+{
+ const bool uffd_wp_changed = (vma->vm_flags ^ flags) & VM_UFFD_WP;
+
+ vma->vm_flags = flags;
+ /*
+ * For shared mappings, we want to enable writenotify while
+ * userfaultfd-wp is enabled (see vma_wants_writenotify()). We'll simply
+ * recalculate vma->vm_page_prot whenever userfaultfd-wp changes.
+ */
+ if ((vma->vm_flags & VM_SHARED) && uffd_wp_changed)
+ vma_set_page_prot(vma);
+}
+
static int userfaultfd_wake_function(wait_queue_entry_t *wq, unsigned mode,
int wake_flags, void *key)
{
@@ -618,7 +633,8 @@ static void userfaultfd_event_wait_compl
for_each_vma(vmi, vma) {
if (vma->vm_userfaultfd_ctx.ctx == release_new_ctx) {
vma->vm_userfaultfd_ctx = NULL_VM_UFFD_CTX;
- vma->vm_flags &= ~__VM_UFFD_FLAGS;
+ userfaultfd_set_vm_flags(vma,
+ vma->vm_flags & ~__VM_UFFD_FLAGS);
}
}
mmap_write_unlock(mm);
@@ -652,7 +668,7 @@ int dup_userfaultfd(struct vm_area_struc
octx = vma->vm_userfaultfd_ctx.ctx;
if (!octx || !(octx->features & UFFD_FEATURE_EVENT_FORK)) {
vma->vm_userfaultfd_ctx = NULL_VM_UFFD_CTX;
- vma->vm_flags &= ~__VM_UFFD_FLAGS;
+ userfaultfd_set_vm_flags(vma, vma->vm_flags & ~__VM_UFFD_FLAGS);
return 0;
}
@@ -733,7 +749,7 @@ void mremap_userfaultfd_prep(struct vm_a
} else {
/* Drop uffd context if remap feature not enabled */
vma->vm_userfaultfd_ctx = NULL_VM_UFFD_CTX;
- vma->vm_flags &= ~__VM_UFFD_FLAGS;
+ userfaultfd_set_vm_flags(vma, vma->vm_flags & ~__VM_UFFD_FLAGS);
}
}
@@ -895,7 +911,7 @@ static int userfaultfd_release(struct in
prev = vma;
}
- vma->vm_flags = new_flags;
+ userfaultfd_set_vm_flags(vma, new_flags);
vma->vm_userfaultfd_ctx = NULL_VM_UFFD_CTX;
}
mmap_write_unlock(mm);
@@ -1463,7 +1479,7 @@ static int userfaultfd_register(struct u
* the next vma was merged into the current one and
* the current one has not been updated yet.
*/
- vma->vm_flags = new_flags;
+ userfaultfd_set_vm_flags(vma, new_flags);
vma->vm_userfaultfd_ctx.ctx = ctx;
if (is_vm_hugetlb_page(vma) && uffd_disable_huge_pmd_share(vma))
@@ -1651,7 +1667,7 @@ static int userfaultfd_unregister(struct
* the next vma was merged into the current one and
* the current one has not been updated yet.
*/
- vma->vm_flags = new_flags;
+ userfaultfd_set_vm_flags(vma, new_flags);
vma->vm_userfaultfd_ctx = NULL_VM_UFFD_CTX;
skip:
--- a/mm/mmap.c~mm-userfaultfd-enable-writenotify-while-userfaultfd-wp-is-enabled-for-a-vma
+++ a/mm/mmap.c
@@ -1524,6 +1524,10 @@ int vma_wants_writenotify(struct vm_area
if (vma_soft_dirty_enabled(vma) && !is_vm_hugetlb_page(vma))
return 1;
+ /* Do we need write faults for uffd-wp tracking? */
+ if (userfaultfd_wp(vma))
+ return 1;
+
/* Specialty mapping? */
if (vm_flags & VM_PFNMAP)
return 0;
_
Patches currently in -mm which might be from david(a)redhat.com are
mm-userfaultfd-rely-on-vma-vm_page_prot-in-uffd_wp_range.patch
mm-userfaultfd-rely-on-vma-vm_page_prot-in-uffd_wp_range-fix.patch
mm-mprotect-drop-pgprot_t-parameter-from-change_protection.patch
mm-mprotect-drop-pgprot_t-parameter-from-change_protection-fix.patch
selftests-vm-cow-add-cow-tests-for-collapsing-of-pte-mapped-anon-thp.patch
mm-nommu-factor-out-check-for-nommu-shared-mappings-into-is_nommu_shared_mapping.patch
mm-nommu-dont-use-vm_mayshare-for-map_private-mappings.patch
drivers-misc-open-dice-dont-touch-vm_mayshare.patch
selftests-mm-define-madv_pageout-to-fix-compilation-issues.patch
The quilt patch titled
Subject: mm/khugepaged: fix collapse_pte_mapped_thp() to allow anon_vma
has been removed from the -mm tree. Its filename was
mm-khugepaged-fix-collapse_pte_mapped_thp-to-allow-anon_vma.patch
This patch was dropped because it was merged into the mm-hotfixes-stable branch
of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
------------------------------------------------------
From: Hugh Dickins <hughd(a)google.com>
Subject: mm/khugepaged: fix collapse_pte_mapped_thp() to allow anon_vma
Date: Thu, 22 Dec 2022 12:41:50 -0800 (PST)
uprobe_write_opcode() uses collapse_pte_mapped_thp() to restore huge pmd,
when removing a breakpoint from hugepage text: vma->anon_vma is always set
in that case, so undo the prohibition. And MADV_COLLAPSE ought to be able
to collapse some page tables in a vma which happens to have anon_vma set
from CoWing elsewhere.
Is anon_vma lock required? Almost not: if any page other than expected
subpage of the non-anon huge page is found in the page table, collapse is
aborted without making any change. However, it is possible that an anon
page was CoWed from this extent in another mm or vma, in which case a
concurrent lookup might look here: so keep it away while clearing pmd (but
perhaps we shall go back to using pmd_lock() there in future).
Note that collapse_pte_mapped_thp() is exceptional in freeing a page table
without having cleared its ptes: I'm uneasy about that, and had thought
pte_clear()ing appropriate; but exclusive i_mmap lock does fix the
problem, and we would have to move the mmu_notification if clearing those
ptes.
What this fixes is not a dangerous instability. But I suggest Cc stable
because uprobes "healing" has regressed in that way, so this should follow
8d3c106e19e8 into those stable releases where it was backported (and may
want adjustment there - I'll supply backports as needed).
Link: https://lkml.kernel.org/r/b740c9fb-edba-92ba-59fb-7a5592e5dfc@google.com
Fixes: 8d3c106e19e8 ("mm/khugepaged: take the right locks for page table retraction")
Signed-off-by: Hugh Dickins <hughd(a)google.com>
Acked-by: David Hildenbrand <david(a)redhat.com>
Cc: Jann Horn <jannh(a)google.com>
Cc: Yang Shi <shy828301(a)gmail.com>
Cc: Zach O'Keefe <zokeefe(a)google.com>
Cc: Song Liu <songliubraving(a)fb.com>
Cc: <stable(a)vger.kernel.org> [5.4+]
Signed-off-by: Andrew Morton <akpm(a)linux-foundation.org>
---
mm/khugepaged.c | 14 ++++++--------
1 file changed, 6 insertions(+), 8 deletions(-)
--- a/mm/khugepaged.c~mm-khugepaged-fix-collapse_pte_mapped_thp-to-allow-anon_vma
+++ a/mm/khugepaged.c
@@ -1460,14 +1460,6 @@ int collapse_pte_mapped_thp(struct mm_st
if (!hugepage_vma_check(vma, vma->vm_flags, false, false, false))
return SCAN_VMA_CHECK;
- /*
- * Symmetry with retract_page_tables(): Exclude MAP_PRIVATE mappings
- * that got written to. Without this, we'd have to also lock the
- * anon_vma if one exists.
- */
- if (vma->anon_vma)
- return SCAN_VMA_CHECK;
-
/* Keep pmd pgtable for uffd-wp; see comment in retract_page_tables() */
if (userfaultfd_wp(vma))
return SCAN_PTE_UFFD_WP;
@@ -1567,8 +1559,14 @@ int collapse_pte_mapped_thp(struct mm_st
}
/* step 4: remove pte entries */
+ /* we make no change to anon, but protect concurrent anon page lookup */
+ if (vma->anon_vma)
+ anon_vma_lock_write(vma->anon_vma);
+
collapse_and_free_pmd(mm, vma, haddr, pmd);
+ if (vma->anon_vma)
+ anon_vma_unlock_write(vma->anon_vma);
i_mmap_unlock_write(vma->vm_file->f_mapping);
maybe_install_pmd:
_
Patches currently in -mm which might be from hughd(a)google.com are
The quilt patch titled
Subject: mm/hugetlb: fix uffd-wp handling for migration entries in hugetlb_change_protection()
has been removed from the -mm tree. Its filename was
mm-hugetlb-fix-uffd-wp-handling-for-migration-entries-in-hugetlb_change_protection.patch
This patch was dropped because it was merged into the mm-hotfixes-stable branch
of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
------------------------------------------------------
From: David Hildenbrand <david(a)redhat.com>
Subject: mm/hugetlb: fix uffd-wp handling for migration entries in hugetlb_change_protection()
Date: Thu, 22 Dec 2022 21:55:11 +0100
We have to update the uffd-wp SWP PTE bit independent of the type of
migration entry. Currently, if we're unlucky and we want to install/clear
the uffd-wp bit just while we're migrating a read-only mapped hugetlb
page, we would miss to set/clear the uffd-wp bit.
Further, if we're processing a readable-exclusive migration entry and
neither want to set or clear the uffd-wp bit, we could currently end up
losing the uffd-wp bit. Note that the same would hold for writable
migrating entries, however, having a writable migration entry with the
uffd-wp bit set would already mean that something went wrong.
Note that the change from !is_readable_migration_entry ->
writable_migration_entry is harmless and actually cleaner, as raised by
Miaohe Lin and discussed in [1].
[1] https://lkml.kernel.org/r/90dd6a93-4500-e0de-2bf0-bf522c311b0c@huawei.com
Link: https://lkml.kernel.org/r/20221222205511.675832-3-david@redhat.com
Fixes: 60dfaad65aa9 ("mm/hugetlb: allow uffd wr-protect none ptes")
Signed-off-by: David Hildenbrand <david(a)redhat.com>
Reviewed-by: Mike Kravetz <mike.kravetz(a)oracle.com>
Cc: Miaohe Lin <linmiaohe(a)huawei.com>
Cc: Muchun Song <muchun.song(a)linux.dev>
Cc: Peter Xu <peterx(a)redhat.com>
Cc: <stable(a)vger.kernel.org>
Signed-off-by: Andrew Morton <akpm(a)linux-foundation.org>
---
mm/hugetlb.c | 17 +++++++++--------
1 file changed, 9 insertions(+), 8 deletions(-)
--- a/mm/hugetlb.c~mm-hugetlb-fix-uffd-wp-handling-for-migration-entries-in-hugetlb_change_protection
+++ a/mm/hugetlb.c
@@ -6662,10 +6662,9 @@ unsigned long hugetlb_change_protection(
} else if (unlikely(is_hugetlb_entry_migration(pte))) {
swp_entry_t entry = pte_to_swp_entry(pte);
struct page *page = pfn_swap_entry_to_page(entry);
+ pte_t newpte = pte;
- if (!is_readable_migration_entry(entry)) {
- pte_t newpte;
-
+ if (is_writable_migration_entry(entry)) {
if (PageAnon(page))
entry = make_readable_exclusive_migration_entry(
swp_offset(entry));
@@ -6673,13 +6672,15 @@ unsigned long hugetlb_change_protection(
entry = make_readable_migration_entry(
swp_offset(entry));
newpte = swp_entry_to_pte(entry);
- if (uffd_wp)
- newpte = pte_swp_mkuffd_wp(newpte);
- else if (uffd_wp_resolve)
- newpte = pte_swp_clear_uffd_wp(newpte);
- set_huge_pte_at(mm, address, ptep, newpte);
pages++;
}
+
+ if (uffd_wp)
+ newpte = pte_swp_mkuffd_wp(newpte);
+ else if (uffd_wp_resolve)
+ newpte = pte_swp_clear_uffd_wp(newpte);
+ if (!pte_same(pte, newpte))
+ set_huge_pte_at(mm, address, ptep, newpte);
} else if (unlikely(is_pte_marker(pte))) {
/* No other markers apply for now. */
WARN_ON_ONCE(!pte_marker_uffd_wp(pte));
_
Patches currently in -mm which might be from david(a)redhat.com are
mm-userfaultfd-rely-on-vma-vm_page_prot-in-uffd_wp_range.patch
mm-userfaultfd-rely-on-vma-vm_page_prot-in-uffd_wp_range-fix.patch
mm-mprotect-drop-pgprot_t-parameter-from-change_protection.patch
mm-mprotect-drop-pgprot_t-parameter-from-change_protection-fix.patch
selftests-vm-cow-add-cow-tests-for-collapsing-of-pte-mapped-anon-thp.patch
mm-nommu-factor-out-check-for-nommu-shared-mappings-into-is_nommu_shared_mapping.patch
mm-nommu-dont-use-vm_mayshare-for-map_private-mappings.patch
drivers-misc-open-dice-dont-touch-vm_mayshare.patch
selftests-mm-define-madv_pageout-to-fix-compilation-issues.patch
The quilt patch titled
Subject: mm/hugetlb: fix PTE marker handling in hugetlb_change_protection()
has been removed from the -mm tree. Its filename was
mm-hugetlb-fix-pte-marker-handling-in-hugetlb_change_protection.patch
This patch was dropped because it was merged into the mm-hotfixes-stable branch
of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
------------------------------------------------------
From: David Hildenbrand <david(a)redhat.com>
Subject: mm/hugetlb: fix PTE marker handling in hugetlb_change_protection()
Date: Thu, 22 Dec 2022 21:55:10 +0100
Patch series "mm/hugetlb: uffd-wp fixes for hugetlb_change_protection()".
Playing with virtio-mem and background snapshots (using uffd-wp) on
hugetlb in QEMU, I managed to trigger a VM_BUG_ON(). Looking into the
details, hugetlb_change_protection() seems to not handle uffd-wp correctly
in all cases.
Patch #1 fixes my test case. I don't have reproducers for patch #2, as it
requires running into migration entries.
I did not yet check in detail yet if !hugetlb code requires similar care.
This patch (of 2):
There are two problematic cases when stumbling over a PTE marker in
hugetlb_change_protection():
(1) We protect an uffd-wp PTE marker a second time using uffd-wp: we will
end up in the "!huge_pte_none(pte)" case and mess up the PTE marker.
(2) We unprotect a uffd-wp PTE marker: we will similarly end up in the
"!huge_pte_none(pte)" case even though we cleared the PTE, because
the "pte" variable is stale. We'll mess up the PTE marker.
For example, if we later stumble over such a "wrongly modified" PTE marker,
we'll treat it like a present PTE that maps some garbage page.
This can, for example, be triggered by mapping a memfd backed by huge
pages, registering uffd-wp, uffd-wp'ing an unmapped page and (a)
uffd-wp'ing it a second time; or (b) uffd-unprotecting it; or (c)
unregistering uffd-wp. Then, ff we trigger fallocate(FALLOC_FL_PUNCH_HOLE)
on that file range, we will run into a VM_BUG_ON:
[ 195.039560] page:00000000ba1f2987 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x0
[ 195.039565] flags: 0x7ffffc0001000(reserved|node=0|zone=0|lastcpupid=0x1fffff)
[ 195.039568] raw: 0007ffffc0001000 ffffe742c0000008 ffffe742c0000008 0000000000000000
[ 195.039569] raw: 0000000000000000 0000000000000000 00000001ffffffff 0000000000000000
[ 195.039569] page dumped because: VM_BUG_ON_PAGE(compound && !PageHead(page))
[ 195.039573] ------------[ cut here ]------------
[ 195.039574] kernel BUG at mm/rmap.c:1346!
[ 195.039579] invalid opcode: 0000 [#1] PREEMPT SMP NOPTI
[ 195.039581] CPU: 7 PID: 4777 Comm: qemu-system-x86 Not tainted 6.0.12-200.fc36.x86_64 #1
[ 195.039583] Hardware name: LENOVO 20WNS1F81N/20WNS1F81N, BIOS N35ET50W (1.50 ) 09/15/2022
[ 195.039584] RIP: 0010:page_remove_rmap+0x45b/0x550
[ 195.039588] Code: [...]
[ 195.039589] RSP: 0018:ffffbc03c3633ba8 EFLAGS: 00010292
[ 195.039591] RAX: 0000000000000040 RBX: ffffe742c0000000 RCX: 0000000000000000
[ 195.039592] RDX: 0000000000000002 RSI: ffffffff8e7aac1a RDI: 00000000ffffffff
[ 195.039592] RBP: 0000000000000001 R08: 0000000000000000 R09: ffffbc03c3633a08
[ 195.039593] R10: 0000000000000003 R11: ffffffff8f146328 R12: ffff9b04c42754b0
[ 195.039594] R13: ffffffff8fcc6328 R14: ffffbc03c3633c80 R15: ffff9b0484ab9100
[ 195.039595] FS: 00007fc7aaf68640(0000) GS:ffff9b0bbf7c0000(0000) knlGS:0000000000000000
[ 195.039596] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 195.039597] CR2: 000055d402c49110 CR3: 0000000159392003 CR4: 0000000000772ee0
[ 195.039598] PKRU: 55555554
[ 195.039599] Call Trace:
[ 195.039600] <TASK>
[ 195.039602] __unmap_hugepage_range+0x33b/0x7d0
[ 195.039605] unmap_hugepage_range+0x55/0x70
[ 195.039608] hugetlb_vmdelete_list+0x77/0xa0
[ 195.039611] hugetlbfs_fallocate+0x410/0x550
[ 195.039612] ? _raw_spin_unlock_irqrestore+0x23/0x40
[ 195.039616] vfs_fallocate+0x12e/0x360
[ 195.039618] __x64_sys_fallocate+0x40/0x70
[ 195.039620] do_syscall_64+0x58/0x80
[ 195.039623] ? syscall_exit_to_user_mode+0x17/0x40
[ 195.039624] ? do_syscall_64+0x67/0x80
[ 195.039626] entry_SYSCALL_64_after_hwframe+0x63/0xcd
[ 195.039628] RIP: 0033:0x7fc7b590651f
[ 195.039653] Code: [...]
[ 195.039654] RSP: 002b:00007fc7aaf66e70 EFLAGS: 00000293 ORIG_RAX: 000000000000011d
[ 195.039655] RAX: ffffffffffffffda RBX: 0000558ef4b7f370 RCX: 00007fc7b590651f
[ 195.039656] RDX: 0000000018000000 RSI: 0000000000000003 RDI: 000000000000000c
[ 195.039657] RBP: 0000000008000000 R08: 0000000000000000 R09: 0000000000000073
[ 195.039658] R10: 0000000008000000 R11: 0000000000000293 R12: 0000000018000000
[ 195.039658] R13: 00007fb8bbe00000 R14: 000000000000000c R15: 0000000000001000
[ 195.039661] </TASK>
Fix it by not going into the "!huge_pte_none(pte)" case if we stumble over
an exclusive marker. spin_unlock() + continue would get the job done.
However, instead, make it clearer that there are no fall-through
statements: we process each case (hwpoison, migration, marker, !none,
none) and then unlock the page table to continue with the next PTE. Let's
avoid "continue" statements and use a single spin_unlock() at the end.
Link: https://lkml.kernel.org/r/20221222205511.675832-1-david@redhat.com
Link: https://lkml.kernel.org/r/20221222205511.675832-2-david@redhat.com
Fixes: 60dfaad65aa9 ("mm/hugetlb: allow uffd wr-protect none ptes")
Signed-off-by: David Hildenbrand <david(a)redhat.com>
Reviewed-by: Peter Xu <peterx(a)redhat.com>
Reviewed-by: Mike Kravetz <mike.kravetz(a)oracle.com>
Cc: Miaohe Lin <linmiaohe(a)huawei.com>
Cc: Muchun Song <muchun.song(a)linux.dev>
Cc: <stable(a)vger.kernel.org>
Signed-off-by: Andrew Morton <akpm(a)linux-foundation.org>
---
mm/hugetlb.c | 21 +++++++--------------
1 file changed, 7 insertions(+), 14 deletions(-)
--- a/mm/hugetlb.c~mm-hugetlb-fix-pte-marker-handling-in-hugetlb_change_protection
+++ a/mm/hugetlb.c
@@ -6658,10 +6658,8 @@ unsigned long hugetlb_change_protection(
}
pte = huge_ptep_get(ptep);
if (unlikely(is_hugetlb_entry_hwpoisoned(pte))) {
- spin_unlock(ptl);
- continue;
- }
- if (unlikely(is_hugetlb_entry_migration(pte))) {
+ /* Nothing to do. */
+ } else if (unlikely(is_hugetlb_entry_migration(pte))) {
swp_entry_t entry = pte_to_swp_entry(pte);
struct page *page = pfn_swap_entry_to_page(entry);
@@ -6682,18 +6680,13 @@ unsigned long hugetlb_change_protection(
set_huge_pte_at(mm, address, ptep, newpte);
pages++;
}
- spin_unlock(ptl);
- continue;
- }
- if (unlikely(pte_marker_uffd_wp(pte))) {
- /*
- * This is changing a non-present pte into a none pte,
- * no need for huge_ptep_modify_prot_start/commit().
- */
+ } else if (unlikely(is_pte_marker(pte))) {
+ /* No other markers apply for now. */
+ WARN_ON_ONCE(!pte_marker_uffd_wp(pte));
if (uffd_wp_resolve)
+ /* Safe to modify directly (non-present->none). */
huge_pte_clear(mm, address, ptep, psize);
- }
- if (!huge_pte_none(pte)) {
+ } else if (!huge_pte_none(pte)) {
pte_t old_pte;
unsigned int shift = huge_page_shift(hstate_vma(vma));
_
Patches currently in -mm which might be from david(a)redhat.com are
mm-userfaultfd-rely-on-vma-vm_page_prot-in-uffd_wp_range.patch
mm-userfaultfd-rely-on-vma-vm_page_prot-in-uffd_wp_range-fix.patch
mm-mprotect-drop-pgprot_t-parameter-from-change_protection.patch
mm-mprotect-drop-pgprot_t-parameter-from-change_protection-fix.patch
selftests-vm-cow-add-cow-tests-for-collapsing-of-pte-mapped-anon-thp.patch
mm-nommu-factor-out-check-for-nommu-shared-mappings-into-is_nommu_shared_mapping.patch
mm-nommu-dont-use-vm_mayshare-for-map_private-mappings.patch
drivers-misc-open-dice-dont-touch-vm_mayshare.patch
selftests-mm-define-madv_pageout-to-fix-compilation-issues.patch
The patch titled
Subject: mm/khugepaged: fix ->anon_vma race
has been added to the -mm mm-hotfixes-unstable branch. Its filename is
mm-khugepaged-fix-anon_vma-race.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patche…
This patch will later appear in the mm-hotfixes-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
Before you just go and hit "reply", please:
a) Consider who else should be cc'ed
b) Prefer to cc a suitable mailing list as well
c) Ideally: find the original patch on the mailing list and do a
reply-to-all to that, adding suitable additional cc's
*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next via the mm-everything
branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
and is updated there every 2-3 working days
------------------------------------------------------
From: Jann Horn <jannh(a)google.com>
Subject: mm/khugepaged: fix ->anon_vma race
Date: Wed, 11 Jan 2023 14:33:51 +0100
If an ->anon_vma is attached to the VMA, collapse_and_free_pmd() requires
it to be locked. retract_page_tables() bails out if an ->anon_vma is
attached, but does this check before holding the mmap lock (as the comment
above the check explains).
If we racily merge an existing ->anon_vma (shared with a child process)
from a neighboring VMA, subsequent rmap traversals on pages belonging to
the child will be able to see the page tables that we are concurrently
removing while assuming that nothing else can access them.
Repeat the ->anon_vma check once we hold the mmap lock to ensure that
there really is no concurrent page table access.
Link: https://lkml.kernel.org/r/20230111133351.807024-1-jannh@google.com
Fixes: f3f0e1d2150b ("khugepaged: add support of collapse for tmpfs/shmem pages")
Signed-off-by: Jann Horn <jannh(a)google.com>
Reported-by: Zach O'Keefe <zokeefe(a)google.com>
Cc: David Hildenbrand <david(a)redhat.com>
Cc: Kirill A. Shutemov <kirill.shutemov(a)linux.intel.com>
Cc: Yang Shi <shy828301(a)gmail.com>
Cc: <stable(a)vger.kernel.org>
Signed-off-by: Andrew Morton <akpm(a)linux-foundation.org>
---
mm/khugepaged.c | 14 +++++++++++++-
1 file changed, 13 insertions(+), 1 deletion(-)
--- a/mm/khugepaged.c~mm-khugepaged-fix-anon_vma-race
+++ a/mm/khugepaged.c
@@ -1642,7 +1642,7 @@ static int retract_page_tables(struct ad
* has higher cost too. It would also probably require locking
* the anon_vma.
*/
- if (vma->anon_vma) {
+ if (READ_ONCE(vma->anon_vma)) {
result = SCAN_PAGE_ANON;
goto next;
}
@@ -1671,6 +1671,18 @@ static int retract_page_tables(struct ad
if ((cc->is_khugepaged || is_target) &&
mmap_write_trylock(mm)) {
/*
+ * Re-check whether we have an ->anon_vma, because
+ * collapse_and_free_pmd() requires that either no
+ * ->anon_vma exists or the anon_vma is locked.
+ * We already checked ->anon_vma above, but that check
+ * is racy because ->anon_vma can be populated under the
+ * mmap lock in read mode.
+ */
+ if (vma->anon_vma) {
+ result = SCAN_PAGE_ANON;
+ goto unlock_next;
+ }
+ /*
* When a vma is registered with uffd-wp, we can't
* recycle the pmd pgtable because there can be pte
* markers installed. Skip it only, so the rest mm/vma
_
Patches currently in -mm which might be from jannh(a)google.com are
mm-khugepaged-fix-anon_vma-race.patch
The patch titled
Subject: maple_tree: fix mas_empty_area_rev() lower bound validation
has been added to the -mm mm-hotfixes-unstable branch. Its filename is
maple_tree-fix-mas_empty_area_rev-lower-bound-validation.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patche…
This patch will later appear in the mm-hotfixes-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
Before you just go and hit "reply", please:
a) Consider who else should be cc'ed
b) Prefer to cc a suitable mailing list as well
c) Ideally: find the original patch on the mailing list and do a
reply-to-all to that, adding suitable additional cc's
*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next via the mm-everything
branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
and is updated there every 2-3 working days
------------------------------------------------------
From: Liam Howlett <liam.howlett(a)oracle.com>
Subject: maple_tree: fix mas_empty_area_rev() lower bound validation
Date: Wed, 11 Jan 2023 20:02:07 +0000
mas_empty_area_rev() was not correctly validating the start of a gap
against the lower limit. This could lead to the range starting lower than
the requested minimum.
Fix the issue by better validating a gap once one is found.
This commit also adds tests to the maple tree test suite for this issue
and tests the mas_empty_area() function for similar bound checking.
Link: https://lkml.kernel.org/r/20230111200136.1851322-1-Liam.Howlett@oracle.com
Link: https://bugzilla.kernel.org/show_bug.cgi?id=216911
Fixes: 54a611b60590 ("Maple Tree: add new data structure")
Signed-off-by: Liam R. Howlett <Liam.Howlett(a)oracle.com>
Reported-by: <amanieu(a)gmail.com>
Link: https://lore.kernel.org/linux-mm/0b9f5425-08d4-8013-aa4c-e620c3b10bb2@leemh…
Cc: <stable(a)vger.kernel.org>
Signed-off-by: Andrew Morton <akpm(a)linux-foundation.org>
---
lib/maple_tree.c | 17 +++----
lib/test_maple_tree.c | 89 ++++++++++++++++++++++++++++++++++++++++
2 files changed, 97 insertions(+), 9 deletions(-)
--- a/lib/maple_tree.c~maple_tree-fix-mas_empty_area_rev-lower-bound-validation
+++ a/lib/maple_tree.c
@@ -4887,7 +4887,7 @@ static bool mas_rev_awalk(struct ma_stat
unsigned long *pivots, *gaps;
void __rcu **slots;
unsigned long gap = 0;
- unsigned long max, min, index;
+ unsigned long max, min;
unsigned char offset;
if (unlikely(mas_is_err(mas)))
@@ -4909,8 +4909,7 @@ static bool mas_rev_awalk(struct ma_stat
min = mas_safe_min(mas, pivots, --offset);
max = mas_safe_pivot(mas, pivots, offset, type);
- index = mas->index;
- while (index <= max) {
+ while (mas->index <= max) {
gap = 0;
if (gaps)
gap = gaps[offset];
@@ -4941,10 +4940,8 @@ static bool mas_rev_awalk(struct ma_stat
min = mas_safe_min(mas, pivots, offset);
}
- if (unlikely(index > max)) {
- mas_set_err(mas, -EBUSY);
- return false;
- }
+ if (unlikely((mas->index > max) || (size - 1 > max - mas->index)))
+ goto no_space;
if (unlikely(ma_is_leaf(type))) {
mas->offset = offset;
@@ -4961,9 +4958,11 @@ static bool mas_rev_awalk(struct ma_stat
return false;
ascend:
- if (mte_is_root(mas->node))
- mas_set_err(mas, -EBUSY);
+ if (!mte_is_root(mas->node))
+ return false;
+no_space:
+ mas_set_err(mas, -EBUSY);
return false;
}
--- a/lib/test_maple_tree.c~maple_tree-fix-mas_empty_area_rev-lower-bound-validation
+++ a/lib/test_maple_tree.c
@@ -2517,6 +2517,91 @@ static noinline void check_bnode_min_spa
mt_set_non_kernel(0);
}
+static noinline void check_empty_area_window(struct maple_tree *mt)
+{
+ unsigned long i, nr_entries = 20;
+ MA_STATE(mas, mt, 0, 0);
+
+ for (i = 1; i <= nr_entries; i++)
+ mtree_store_range(mt, i*10, i*10 + 9,
+ xa_mk_value(i), GFP_KERNEL);
+
+ /* Create another hole besides the one at 0 */
+ mtree_store_range(mt, 160, 169, NULL, GFP_KERNEL);
+
+ /* Check lower bounds that don't fit */
+ rcu_read_lock();
+ MT_BUG_ON(mt, mas_empty_area_rev(&mas, 5, 90, 10) != -EBUSY);
+
+ mas_reset(&mas);
+ MT_BUG_ON(mt, mas_empty_area_rev(&mas, 6, 90, 5) != -EBUSY);
+
+ /* Check lower bound that does fit */
+ mas_reset(&mas);
+ MT_BUG_ON(mt, mas_empty_area_rev(&mas, 5, 90, 5) != 0);
+ MT_BUG_ON(mt, mas.index != 5);
+ MT_BUG_ON(mt, mas.last != 9);
+ rcu_read_unlock();
+
+ /* Check one gap that doesn't fit and one that does */
+ rcu_read_lock();
+ mas_reset(&mas);
+ MT_BUG_ON(mt, mas_empty_area_rev(&mas, 5, 217, 9) != 0);
+ MT_BUG_ON(mt, mas.index != 161);
+ MT_BUG_ON(mt, mas.last != 169);
+
+ /* Check one gap that does fit above the min */
+ mas_reset(&mas);
+ MT_BUG_ON(mt, mas_empty_area_rev(&mas, 100, 218, 3) != 0);
+ MT_BUG_ON(mt, mas.index != 216);
+ MT_BUG_ON(mt, mas.last != 218);
+
+ /* Check size that doesn't fit any gap */
+ mas_reset(&mas);
+ MT_BUG_ON(mt, mas_empty_area_rev(&mas, 100, 218, 16) != -EBUSY);
+
+ /*
+ * Check size that doesn't fit the lower end of the window but
+ * does fit the gap
+ */
+ mas_reset(&mas);
+ MT_BUG_ON(mt, mas_empty_area_rev(&mas, 167, 200, 4) != -EBUSY);
+
+ /*
+ * Check size that doesn't fit the upper end of the window but
+ * does fit the gap
+ */
+ mas_reset(&mas);
+ MT_BUG_ON(mt, mas_empty_area_rev(&mas, 100, 162, 4) != -EBUSY);
+
+ /* Check mas_empty_area forward */
+ mas_reset(&mas);
+ MT_BUG_ON(mt, mas_empty_area(&mas, 0, 100, 9) != 0);
+ MT_BUG_ON(mt, mas.index != 0);
+ MT_BUG_ON(mt, mas.last != 8);
+
+ mas_reset(&mas);
+ MT_BUG_ON(mt, mas_empty_area(&mas, 0, 100, 4) != 0);
+ MT_BUG_ON(mt, mas.index != 0);
+ MT_BUG_ON(mt, mas.last != 3);
+
+ mas_reset(&mas);
+ MT_BUG_ON(mt, mas_empty_area(&mas, 0, 100, 11) != -EBUSY);
+
+ mas_reset(&mas);
+ MT_BUG_ON(mt, mas_empty_area(&mas, 5, 100, 6) != -EBUSY);
+
+ mas_reset(&mas);
+ MT_BUG_ON(mt, mas_empty_area(&mas, 0, 8, 10) != -EBUSY);
+
+ mas_reset(&mas);
+ mas_empty_area(&mas, 100, 165, 3);
+
+ mas_reset(&mas);
+ MT_BUG_ON(mt, mas_empty_area(&mas, 100, 163, 6) != -EBUSY);
+ rcu_read_unlock();
+}
+
static DEFINE_MTREE(tree);
static int maple_tree_seed(void)
{
@@ -2765,6 +2850,10 @@ static int maple_tree_seed(void)
check_bnode_min_spanning(&tree);
mtree_destroy(&tree);
+ mt_init_flags(&tree, MT_FLAGS_ALLOC_RANGE);
+ check_empty_area_window(&tree);
+ mtree_destroy(&tree);
+
#if defined(BENCH)
skip:
#endif
_
Patches currently in -mm which might be from liam.howlett(a)oracle.com are
nommu-fix-memory-leak-in-do_mmap-error-path.patch
nommu-fix-do_munmap-error-path.patch
nommu-fix-split_vma-map_count-error.patch
maple_tree-fix-mas_empty_area_rev-lower-bound-validation.patch
maple_tree-remove-gfp_zero-from-kmem_cache_alloc-and-kmem_cache_alloc_bulk.patch
Happy new 2023,
I normally watch [1] for the next LTS linux-kernel which is for me an
official site and for an official announcement.
On the debian-kernel mailing list you read Linux 6.1 will be the
official one for Debian-12 aka bookworm.
I saw a phoronix article about EOL of Linux-4.9 [3] which points to [2].
[2] says:
After being prompted on the kernel mailing list, Linux stable
maintainer Greg Kroah-Hartman commented:
> I usually pick the "last kernel of the year", and based on the normal release cycle, yes, 6.1 will be that kernel.
> But I can't promise anything until it is released, for obvious reasons.
This is not a clear statement for me and was maybe at a point where
6.1 was not released.
If you published a clear statement please point me to it.
And if so, please update [1] accordingly.
( It dropped 4.9 from LTS list recently from [1] - guess Konstantin or
someone from helpdesk did - so [1] is actively maintained. )
Please, a clear statement.
Thanks.
Regards,
-Sedat-
P.S.: Just for the records: I am not subscribed to LKML or
linux-stable mailing-lists and may miss such a clear statement.
[1] https://kernel.org/category/releases.html
[2] https://www.phoronix.com/news/Linux-6.1-Likely-LTS
[3] https://www.phoronix.com/news/Linux-4.9.337-LTS-Over
[4] https://release.debian.org/ > Key release dates