From 87e8827b37c0c391d9915d0dc6a06c9b5f9cac65 Mon Sep 17 00:00:00 2001 From: Oleg Nesterov Date: Thu, 5 Nov 2015 18:48:14 -0800 Subject: [PATCH] mm: fix the racy mm->locked_vm change in "mm->locked_vm += grow" and vm_stat_account() in acct_stack_growth() are not safe; multiple threads using the same ->mm can do this at the same time trying to expans different vma's under down_read(mmap_sem). This means that one of the "locked_vm += grow" changes can be lost and we can miss munlock_vma_pages_all() later. Move this code into the caller(s) under mm->page_table_lock. All other updates to ->locked_vm hold mmap_sem for writing. Signed-off-by: Oleg Nesterov Acked-by: Hugh Dickins Cc: Andrey Konovalov Cc: Davidlohr Bueso Cc: "Kirill A. Shutemov" Cc: Sasha Levin Cc: Vlastimil Babka Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/mmap.c | 12 ++++++++---- 1 file changed, 8 insertions(+), 4 deletions(-) diff --git a/mm/mmap.c b/mm/mmap.c index 3ec19b601be0..d1ac22485998 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -2138,10 +2138,6 @@ static int acct_stack_growth(struct vm_area_struct *vma, unsigned long size, uns if (security_vm_enough_memory_mm(mm, grow)) return -ENOMEM; - /* Ok, everything looks good - let it rip */ - if (vma->vm_flags & VM_LOCKED) - mm->locked_vm += grow; - vm_stat_account(mm, vma->vm_flags, vma->vm_file, grow); return 0; } @@ -2202,6 +2198,10 @@ int expand_upwards(struct vm_area_struct *vma, unsigned long address) * against concurrent vma expansions. */ spin_lock(&vma->vm_mm->page_table_lock); + if (vma->vm_flags & VM_LOCKED) + vma->vm_mm->locked_vm += grow; + vm_stat_account(vma->vm_mm, vma->vm_flags, + vma->vm_file, grow); anon_vma_interval_tree_pre_update_vma(vma); vma->vm_end = address; anon_vma_interval_tree_post_update_vma(vma); @@ -2273,6 +2273,10 @@ int expand_downwards(struct vm_area_struct *vma, * against concurrent vma expansions. */ spin_lock(&vma->vm_mm->page_table_lock); + if (vma->vm_flags & VM_LOCKED) + vma->vm_mm->locked_vm += grow; + vm_stat_account(vma->vm_mm, vma->vm_flags, + vma->vm_file, grow); anon_vma_interval_tree_pre_update_vma(vma); vma->vm_start = address; vma->vm_pgoff -= grow; -- GitLab