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mm: fix the racy mm->locked_vm change in

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"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 <oleg@redhat.com>
Acked-by: Hugh Dickins <hughd@google.com>
Cc: Andrey Konovalov <andreyknvl@google.com>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: "Kirill A. Shutemov" <kirill@shutemov.name>
Cc: Sasha Levin <sasha.levin@oracle.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Oleg Nesterov 2015-11-05 18:48:14 -08:00 committed by Linus Torvalds
parent 9fd745d450
commit 87e8827b37
1 changed files with 8 additions and 4 deletions
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12
mm/mmap.c
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@ -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;