From 3c6748cd516ff009a3d8dac1d4cdc2ade6d218a7 Mon Sep 17 00:00:00 2001 From: Suren Baghdasaryan Date: Mon, 27 Feb 2023 09:36:20 -0800 Subject: [PATCH] UPSTREAM: mm/mmap: prevent pagefault handler from racing with mmu_notifier registration 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. Link: https://lkml.kernel.org/r/20230227173632.3292573-22-surenb@google.com Signed-off-by: Suren Baghdasaryan Signed-off-by: Andrew Morton (cherry picked from commit eeff9a5d47f89bc641034fea05501c8a6de131cb) Bug: 161210518 Change-Id: I4176bf0e1b07f03dfc1ac7dd37d7941d5a1dbc02 Signed-off-by: Suren Baghdasaryan --- mm/mmap.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/mm/mmap.c b/mm/mmap.c index 192821327eb5..ed1fc3927157 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -3592,6 +3592,7 @@ 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 * @@ -3614,6 +3615,13 @@ 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; @@ -3703,6 +3711,7 @@ 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); }