From: Simon Guo <wei.guo.simon@xxxxxxxxx> Subject: 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: 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/1472554781-9835-3-git-send-email-wei.guo.simon@xxxxxxxxx Signed-off-by: Simon Guo <wei.guo.simon@xxxxxxxxx> Acked-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx> Cc: Alexey Klimov <klimov.linux@xxxxxxxxx> Cc: Eric B Munson <emunson@xxxxxxxxxx> Cc: Geert Uytterhoeven <geert@xxxxxxxxxxxxxx> Cc: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx> Cc: Michal Hocko <mhocko@xxxxxxxx> Cc: Shuah Khan <shuah@xxxxxxxxxx> Cc: Simon Guo <wei.guo.simon@xxxxxxxxx> Cc: Thierry Reding <treding@xxxxxxxxxx> Cc: Vlastimil Babka <vbabka@xxxxxxx> Cc: David Rientjes <rientjes@xxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/mlock.c | 3 +++ 1 file changed, 3 insertions(+) diff -puN mm/mlock.c~mm-mlock-avoid-increase-mm-locked_vm-on-mlock-when-already-mlock2mlock_onfault mm/mlock.c --- a/mm/mlock.c~mm-mlock-avoid-increase-mm-locked_vm-on-mlock-when-already-mlock2mlock_onfault +++ a/mm/mlock.c @@ -516,6 +516,7 @@ 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)) @@ -550,6 +551,8 @@ 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; /* _ -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
