4.4-stable review patch. If anyone has any objections, please let me know.
------------------ From: Simon Guo <[email protected]> commit b155b4fde5bdde9fed439cd1f5ea07173df2ed31 upstream. 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: mlock2(p, 1024 * 64, MLOCK_ONFAULT); //VM_LOCKED|VM_LOCKONFAULT 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: http://lkml.kernel.org/r/[email protected] Signed-off-by: Simon Guo <[email protected]> Acked-by: Kirill A. Shutemov <[email protected]> Cc: Alexey Klimov <[email protected]> Cc: Eric B Munson <[email protected]> Cc: Geert Uytterhoeven <[email protected]> Cc: Mel Gorman <[email protected]> Cc: Michal Hocko <[email protected]> Cc: Shuah Khan <[email protected]> Cc: Simon Guo <[email protected]> Cc: Thierry Reding <[email protected]> Cc: Vlastimil Babka <[email protected]> Cc: David Rientjes <[email protected]> Signed-off-by: Andrew Morton <[email protected]> Signed-off-by: Linus Torvalds <[email protected]> Cc: Rafael David Tinoco <[email protected]> Signed-off-by: Greg Kroah-Hartman <[email protected]> --- mm/mlock.c | 3 +++ 1 file changed, 3 insertions(+) --- a/mm/mlock.c +++ b/mm/mlock.c @@ -504,6 +504,7 @@ static int mlock_fixup(struct vm_area_st 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)) @@ -538,6 +539,8 @@ success: 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; /*
