Commit 7d310301 authored by Jann Horn's avatar Jann Horn Committed by Wupeng Ma
Browse files

mm/khugepaged: invoke MMU notifiers in shmem/file collapse paths 

stable inclusion
from stable-v5.10.159
commit 7f445ca2e0e59c7971d0b7b853465e50844ab596
category: bugfix
bugzilla: https://gitee.com/src-openeuler/kernel/issues/IAYREP
CVE: CVE-2022-48991

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=7f445ca2e0e59c7971d0b7b853465e50844ab596

--------------------------------

commit f268f6cf upstream.

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 f3f0e1d2
("khugepaged: add support of collapse for tmpfs/shmem pages"), but most of
the security impact of this only came in commit 27e1f827 ("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/20221129154730.2274278-3-jannh@google.com
Link: https://lkml.kernel.org/r/20221128180252.1684965-3-jannh@google.com
Link: https://lkml.kernel.org/r/20221125213714.4115729-3-jannh@google.com


Fixes: f3f0e1d2 ("khugepaged: add support of collapse for tmpfs/shmem pages")
Signed-off-by: default avatarJann Horn <jannh@google.com>
Acked-by: default avatarDavid Hildenbrand <david@redhat.com>
Reviewed-by: default avatarYang Shi <shy828301@gmail.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
[manual backport: this code was refactored from two copies into a common
helper between 5.15 and 6.0]
Signed-off-by: default avatarJann Horn <jannh@google.com>
Signed-off-by: default avatarSasha Levin <sashal@kernel.org>

Conflicts:
	mm/khugepaged.c
[Ma Wupeng: conflicts context is tring to use right lock, not MMU related]
Signed-off-by: default avatarMa Wupeng <mawupeng1@huawei.com>
parent b55d1f03

mm/khugepaged.c

+13 −0
Original line number Diff line number Diff line
@@ -1454,6 +1454,7 @@ void collapse_pte_mapped_thp(struct mm_struct *mm, unsigned long addr) 
	spinlock_t *ptl;

	int count = 0;

	int i;

	struct mmu_notifier_range range;



	if (!vma || !vma->vm_file ||

	    vma->vm_start > haddr || vma->vm_end < haddr + HPAGE_PMD_SIZE)
@@ -1528,9 +1529,13 @@ void collapse_pte_mapped_thp(struct mm_struct *mm, unsigned long addr) 


	/* step 4: collapse pmd */

	ptl = pmd_lock(vma->vm_mm, pmd);

	mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, NULL, mm, haddr,

				haddr + HPAGE_PMD_SIZE);

	mmu_notifier_invalidate_range_start(&range);

	_pmd = pmdp_collapse_flush(vma, haddr, pmd);

	spin_unlock(ptl);

	mm_dec_nr_ptes(mm);

	mmu_notifier_invalidate_range_end(&range);

	pte_free(mm, pmd_pgtable(_pmd));



drop_hpage:
@@ -1612,11 +1617,19 @@ static void retract_page_tables(struct address_space *mapping, pgoff_t pgoff) 
		if (mmap_write_trylock(mm)) {

			if (!khugepaged_test_exit(mm)) {

				spinlock_t *ptl = pmd_lock(mm, pmd);

				struct mmu_notifier_range range;



				mmu_notifier_range_init(&range,

							MMU_NOTIFY_CLEAR, 0,

							NULL, mm, addr,

							addr + HPAGE_PMD_SIZE);

				mmu_notifier_invalidate_range_start(&range);

				/* assume page table is clear */

				_pmd = pmdp_collapse_flush(vma, addr, pmd);

				spin_unlock(ptl);

				mm_dec_nr_ptes(mm);

				pte_free(mm, pmd_pgtable(_pmd));

				mmu_notifier_invalidate_range_end(&range);

			}

			mmap_write_unlock(mm);

		} else {