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The patch titled
Subject: mm/khugepaged: invoke MMU notifiers in shmem/file collapse paths
has been added to the -mm mm-hotfixes-unstable branch. Its filename is
mm-khugepaged-invoke-mmu-notifiers-in-shmem-file-collapse-paths.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: invoke MMU notifiers in shmem/file collapse paths
Date: Fri, 25 Nov 2022 22:37:14 +0100
Any codepath that zaps page table entries must invoke MMU notifiers to
ensure that secondary MMUs (like KVM) don't keep accessing pages which
aren't mapped anymore. Secondary MMUs don't hold their own references to
pages that are mirrored over, so failing to notify them can lead to page
use-after-free.
I'm marking this as addressing an issue introduced in commit f3f0e1d2150b
("khugepaged: add support of collapse for tmpfs/shmem pages"), but most of
the security impact of this only came in commit 27e1f8273113 ("khugepaged:
enable collapse pmd for pte-mapped THP"), which actually omitted flushes
for the removal of present PTEs, not just for the removal of empty page
tables.
Link: https://lkml.kernel.org/r/20221125213714.4115729-3-jannh@google.com
Fixes: f3f0e1d2150b ("khugepaged: add support of collapse for tmpfs/shmem pages")
Signed-off-by: Jann Horn <jannh(a)google.com>
Cc: David Hildenbrand <david(a)redhat.com>
Cc: John Hubbard <jhubbard(a)nvidia.com>
Cc: Peter Xu <peterx(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/khugepaged.c | 5 +++++
1 file changed, 5 insertions(+)
--- a/mm/khugepaged.c~mm-khugepaged-invoke-mmu-notifiers-in-shmem-file-collapse-paths
+++ a/mm/khugepaged.c
@@ -1399,6 +1399,7 @@ static void collapse_and_free_pmd(struct
unsigned long addr, pmd_t *pmdp)
{
pmd_t pmd;
+ struct mmu_notifier_range range;
mmap_assert_write_locked(mm);
if (vma->vm_file)
@@ -1410,8 +1411,12 @@ static void collapse_and_free_pmd(struct
if (vma->anon_vma)
lockdep_assert_held_write(&vma->anon_vma->root->rwsem);
+ mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, NULL, mm, addr,
+ addr + HPAGE_PMD_SIZE);
+ mmu_notifier_invalidate_range_start(&range);
pmd = pmdp_collapse_flush(vma, addr, pmdp);
tlb_remove_table_sync_one();
+ mmu_notifier_invalidate_range_end(&range);
mm_dec_nr_ptes(mm);
page_table_check_pte_clear_range(mm, addr, pmd);
pte_free(mm, pmd_pgtable(pmd));
_
Patches currently in -mm which might be from jannh(a)google.com are
mm-khugepaged-take-the-right-locks-for-page-table-retraction.patch
mm-khugepaged-fix-gup-fast-interaction-by-sending-ipi.patch
mm-khugepaged-invoke-mmu-notifiers-in-shmem-file-collapse-paths.patch
The patch titled
Subject: mm/khugepaged: fix GUP-fast interaction by sending IPI
has been added to the -mm mm-hotfixes-unstable branch. Its filename is
mm-khugepaged-fix-gup-fast-interaction-by-sending-ipi.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 GUP-fast interaction by sending IPI
Date: Fri, 25 Nov 2022 22:37:13 +0100
Since commit 70cbc3cc78a99 ("mm: gup: fix the fast GUP race against THP
collapse"), the lockless_pages_from_mm() fastpath rechecks the pmd_t to
ensure that the page table was not removed by khugepaged in between.
However, lockless_pages_from_mm() still requires that the page table is
not concurrently freed. Fix it by sending IPIs (if the architecture uses
semi-RCU-style page table freeing) before freeing/reusing page tables.
Link: https://lkml.kernel.org/r/20221125213714.4115729-2-jannh@google.com
Fixes: ba76149f47d8 ("thp: khugepaged")
Signed-off-by: Jann Horn <jannh(a)google.com>
Cc: David Hildenbrand <david(a)redhat.com>
Cc: John Hubbard <jhubbard(a)nvidia.com>
Cc: Peter Xu <peterx(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>
---
include/asm-generic/tlb.h | 4 ++++
mm/khugepaged.c | 2 ++
mm/mmu_gather.c | 4 +---
3 files changed, 7 insertions(+), 3 deletions(-)
--- a/include/asm-generic/tlb.h~mm-khugepaged-fix-gup-fast-interaction-by-sending-ipi
+++ a/include/asm-generic/tlb.h
@@ -222,12 +222,16 @@ extern void tlb_remove_table(struct mmu_
#define tlb_needs_table_invalidate() (true)
#endif
+void tlb_remove_table_sync_one(void);
+
#else
#ifdef tlb_needs_table_invalidate
#error tlb_needs_table_invalidate() requires MMU_GATHER_RCU_TABLE_FREE
#endif
+static inline void tlb_remove_table_sync_one(void) { }
+
#endif /* CONFIG_MMU_GATHER_RCU_TABLE_FREE */
--- a/mm/khugepaged.c~mm-khugepaged-fix-gup-fast-interaction-by-sending-ipi
+++ a/mm/khugepaged.c
@@ -1051,6 +1051,7 @@ static int collapse_huge_page(struct mm_
_pmd = pmdp_collapse_flush(vma, address, pmd);
spin_unlock(pmd_ptl);
mmu_notifier_invalidate_range_end(&range);
+ tlb_remove_table_sync_one();
spin_lock(pte_ptl);
result = __collapse_huge_page_isolate(vma, address, pte, cc,
@@ -1410,6 +1411,7 @@ static void collapse_and_free_pmd(struct
lockdep_assert_held_write(&vma->anon_vma->root->rwsem);
pmd = pmdp_collapse_flush(vma, addr, pmdp);
+ tlb_remove_table_sync_one();
mm_dec_nr_ptes(mm);
page_table_check_pte_clear_range(mm, addr, pmd);
pte_free(mm, pmd_pgtable(pmd));
--- a/mm/mmu_gather.c~mm-khugepaged-fix-gup-fast-interaction-by-sending-ipi
+++ a/mm/mmu_gather.c
@@ -153,7 +153,7 @@ static void tlb_remove_table_smp_sync(vo
/* Simply deliver the interrupt */
}
-static void tlb_remove_table_sync_one(void)
+void tlb_remove_table_sync_one(void)
{
/*
* This isn't an RCU grace period and hence the page-tables cannot be
@@ -177,8 +177,6 @@ static void tlb_remove_table_free(struct
#else /* !CONFIG_MMU_GATHER_RCU_TABLE_FREE */
-static void tlb_remove_table_sync_one(void) { }
-
static void tlb_remove_table_free(struct mmu_table_batch *batch)
{
__tlb_remove_table_free(batch);
_
Patches currently in -mm which might be from jannh(a)google.com are
mm-khugepaged-take-the-right-locks-for-page-table-retraction.patch
mm-khugepaged-fix-gup-fast-interaction-by-sending-ipi.patch
mm-khugepaged-invoke-mmu-notifiers-in-shmem-file-collapse-paths.patch