4.4-stable review patch. If anyone has any objections, please let me know.
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From: Simon Guo wei.guo.simon@gmail.com
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/1472554781-9835-3-git-send-email-wei.guo.simon@gmai... Signed-off-by: Simon Guo wei.guo.simon@gmail.com Acked-by: Kirill A. Shutemov kirill.shutemov@linux.intel.com Cc: Alexey Klimov klimov.linux@gmail.com Cc: Eric B Munson emunson@akamai.com Cc: Geert Uytterhoeven geert@linux-m68k.org Cc: Mel Gorman mgorman@techsingularity.net Cc: Michal Hocko mhocko@suse.com Cc: Shuah Khan shuah@kernel.org Cc: Simon Guo wei.guo.simon@gmail.com Cc: Thierry Reding treding@nvidia.com Cc: Vlastimil Babka vbabka@suse.cz Cc: David Rientjes rientjes@google.com Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Linus Torvalds torvalds@linux-foundation.org Cc: Rafael David Tinoco rafael.tinoco@linaro.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- 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;
/*