[PATCH v4 21/33] mm/mmap: prevent pagefault handler from racing with mmu_notifier registration
From: Suren Baghdasaryan <surenb@google.com>
Date: 2023-02-27 17:38:39
Also in:
linux-mm, lkml
Subsystem:
memory management, memory mapping, the rest · Maintainers:
Andrew Morton, Liam R. Howlett, Lorenzo Stoakes, Linus Torvalds
Page fault handlers might need to fire MMU notifications while a new notifier is being registered. Modify mm_take_all_locks to write-lock all VMAs and prevent this race with page fault handlers that would hold VMA locks. VMAs are locked before i_mmap_rwsem and anon_vma to keep the same locking order as in page fault handlers. Signed-off-by: Suren Baghdasaryan <surenb@google.com> --- mm/mmap.c | 9 +++++++++ 1 file changed, 9 insertions(+)
diff --git a/mm/mmap.c b/mm/mmap.c
index ec745586785c..b947d82e8522 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c@@ -3486,6 +3486,7 @@ static void vm_lock_mapping(struct mm_struct *mm, struct address_space *mapping) * of mm/rmap.c: * - all hugetlbfs_i_mmap_rwsem_key locks (aka mapping->i_mmap_rwsem for * hugetlb mapping); + * - all vmas marked locked * - all i_mmap_rwsem locks; * - all anon_vma->rwseml *
@@ -3508,6 +3509,13 @@ int mm_take_all_locks(struct mm_struct *mm) mutex_lock(&mm_all_locks_mutex); + mas_for_each(&mas, vma, ULONG_MAX) { + if (signal_pending(current)) + goto out_unlock; + vma_start_write(vma); + } + + mas_set(&mas, 0); mas_for_each(&mas, vma, ULONG_MAX) { if (signal_pending(current)) goto out_unlock;
@@ -3597,6 +3605,7 @@ void mm_drop_all_locks(struct mm_struct *mm) if (vma->vm_file && vma->vm_file->f_mapping) vm_unlock_mapping(vma->vm_file->f_mapping); } + vma_end_write_all(mm); mutex_unlock(&mm_all_locks_mutex); }
--
2.39.2.722.g9855ee24e9-goog