diff options
Diffstat (limited to 'mm/userfaultfd.c')
| -rw-r--r-- | mm/userfaultfd.c | 11 |
1 files changed, 9 insertions, 2 deletions
diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c index 1b0d7abad1d4..bd96855f3961 100644 --- a/mm/userfaultfd.c +++ b/mm/userfaultfd.c @@ -276,10 +276,14 @@ retry: BUG_ON(dst_addr >= dst_start + len); /* - * Serialize via hugetlb_fault_mutex + * Serialize via i_mmap_rwsem and hugetlb_fault_mutex. + * i_mmap_rwsem ensures the dst_pte remains valid even + * in the case of shared pmds. fault mutex prevents + * races with other faulting threads. */ - idx = linear_page_index(dst_vma, dst_addr); mapping = dst_vma->vm_file->f_mapping; + i_mmap_lock_read(mapping); + idx = linear_page_index(dst_vma, dst_addr); hash = hugetlb_fault_mutex_hash(mapping, idx); mutex_lock(&hugetlb_fault_mutex_table[hash]); @@ -287,6 +291,7 @@ retry: dst_pte = huge_pte_alloc(dst_mm, dst_addr, vma_hpagesize); if (!dst_pte) { mutex_unlock(&hugetlb_fault_mutex_table[hash]); + i_mmap_unlock_read(mapping); goto out_unlock; } @@ -294,6 +299,7 @@ retry: dst_pteval = huge_ptep_get(dst_pte); if (!huge_pte_none(dst_pteval)) { mutex_unlock(&hugetlb_fault_mutex_table[hash]); + i_mmap_unlock_read(mapping); goto out_unlock; } @@ -301,6 +307,7 @@ retry: dst_addr, src_addr, &page); mutex_unlock(&hugetlb_fault_mutex_table[hash]); + i_mmap_unlock_read(mapping); vm_alloc_shared = vm_shared; cond_resched(); |