From: Jann Horn jannh@google.com
stable inclusion from stable-v4.19.270 commit ff2a1a6f869650aec99e9d070b5ab625bfbc5bc3 category: bugfix bugzilla: https://gitee.com/openeuler/kernel/issues/I6DPF8 CVE: NA
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commit f268f6cf875f3220afc77bdd0bf1bb136eb54db9 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 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/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: f3f0e1d2150b ("khugepaged: add support of collapse for tmpfs/shmem pages") Signed-off-by: Jann Horn jannh@google.com Acked-by: David Hildenbrand david@redhat.com Reviewed-by: Yang Shi shy828301@gmail.com Cc: John Hubbard jhubbard@nvidia.com Cc: Peter Xu peterx@redhat.com Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org [manual backport: this code was refactored from two copies into a common helper between 5.15 and 6.0; pmd collapse for PTE-mapped THP was only added in 5.4; MMU notifier API changed between 4.19 and 5.4] Signed-off-by: Jann Horn jannh@google.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org Signed-off-by: Ma Wupeng mawupeng1@huawei.com Reviewed-by: tong tiangen tongtiangen@huawei.com Signed-off-by: Yongqiang Liu liuyongqiang13@huawei.com --- mm/khugepaged.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-)
diff --git a/mm/khugepaged.c b/mm/khugepaged.c index 83500fe19572..04d0a3ee006e 100644 --- a/mm/khugepaged.c +++ b/mm/khugepaged.c @@ -1327,13 +1327,20 @@ static void retract_page_tables(struct address_space *mapping, pgoff_t pgoff) */ if (down_write_trylock(&mm->mmap_sem)) { if (!khugepaged_test_exit(mm)) { - spinlock_t *ptl = pmd_lock(mm, pmd); + spinlock_t *ptl; + unsigned long end = addr + HPAGE_PMD_SIZE; + + mmu_notifier_invalidate_range_start(mm, addr, + end); + ptl = pmd_lock(mm, pmd); /* assume page table is clear */ _pmd = pmdp_collapse_flush(vma, addr, pmd); spin_unlock(ptl); mm_dec_nr_ptes(mm); tlb_remove_table_sync_one(); pte_free(mm, pmd_pgtable(_pmd)); + mmu_notifier_invalidate_range_end(mm, addr, + end); } up_write(&mm->mmap_sem); }