Commit b155b4fd authored by Simon Guo's avatar Simon Guo Committed by Linus Torvalds

mm: mlock: avoid increase mm->locked_vm on mlock() when already mlock2(,MLOCK_ONFAULT)

When one vma was with flag VM_LOCKED|VM_LOCKONFAULT (by invoking
mlock2(,MLOCK_ONFAULT)), it can again be populated with mlock() with
VM_LOCKED flag only.

There is a hole in mlock_fixup() which increase mm->locked_vm twice even
the two operations are on the same vma and both with VM_LOCKED flags.

The issue can be reproduced by following code:

  mlock(p, 1024 * 64);  //VM_LOCKED

Then check the increase VmLck field in /proc/pid/status(to 128k).

When vma is set with different vm_flags, and the new vm_flags is with
VM_LOCKED, it is not necessarily be a "new locked" vma.  This patch
corrects this bug by prevent mm->locked_vm from increment when old
vm_flags is already VM_LOCKED.

Link: 's avatarSimon Guo <>
Acked-by: 's avatarKirill A. Shutemov <>
Cc: Alexey Klimov <>
Cc: Eric B Munson <>
Cc: Geert Uytterhoeven <>
Cc: Mel Gorman <>
Cc: Michal Hocko <>
Cc: Shuah Khan <>
Cc: Simon Guo <>
Cc: Thierry Reding <>
Cc: Vlastimil Babka <>
Cc: David Rientjes <>
Signed-off-by: 's avatarAndrew Morton <>
Signed-off-by: 's avatarLinus Torvalds <>
parent 0cf2f6f6
......@@ -516,6 +516,7 @@ static int mlock_fixup(struct vm_area_struct *vma, struct vm_area_struct **prev,
int nr_pages;
int ret = 0;
int lock = !!(newflags & VM_LOCKED);
vm_flags_t old_flags = vma->vm_flags;
if (newflags == vma->vm_flags || (vma->vm_flags & VM_SPECIAL) ||
is_vm_hugetlb_page(vma) || vma == get_gate_vma(current->mm))
......@@ -550,6 +551,8 @@ static int mlock_fixup(struct vm_area_struct *vma, struct vm_area_struct **prev,
nr_pages = (end - start) >> PAGE_SHIFT;
if (!lock)
nr_pages = -nr_pages;
else if (old_flags & VM_LOCKED)
nr_pages = 0;
mm->locked_vm += nr_pages;
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