Re: [mmotm:master 120/306] fs/proc/task_mmu.c:474 smaps_account() warn: should 'size << 12' be a 64 bit type?

["Kirill A. Shutemov" <kirill@shutemov.name>]

On Fri, Nov 14, 2014 at 02:44:15PM +0300, kbuild test robot wrote:
> [ You would have to enable transparent huge page tables on a 32 bit
>   system to trigger this bug and I don't think that's possible.

It is. We have THP on 32-bit x86.

>   I don't think Smatch will complain about this if you have the cross
>   function database turned on because it knows the value of size in that
>   case.  But most people don't build the database so it might be worth
>   silencing this bug?  Should I even bother sending these email for
>   non-bugs?  Let me know.  -dan ]
> 
> tree:   git://git.cmpxchg.org/linux-mmotm.git master
> head:   e668fb4c5c5e6de5b9432bd36d83b3a0b4ce78e8
> commit: be7c8db9daa43935912bc8c898ecea99b32d805b [120/306] mm: fix huge zero page accounting in smaps report
> 
> fs/proc/task_mmu.c:474 smaps_account() warn: should 'size << 12' be a 64 bit type?

This should fix the issue.

diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 8fd00743bd4d..de80a887d98e 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -464,17 +464,16 @@ static void smaps_account(struct mem_size_stats *mss, struct page *page,
                        mss->shared_dirty += size;
                else
                        mss->shared_clean += size;
-               mss->pss += (size << PSS_SHIFT) / mapcount;
+               mss->pss += ((u64)size << PSS_SHIFT) / mapcount;
        } else {
                if (dirty || PageDirty(page))
                        mss->private_dirty += size;
                else
                        mss->private_clean += size;
-               mss->pss += (size << PSS_SHIFT);
+               mss->pss += (u64)size << PSS_SHIFT;
        }
 }
 
-
 static void smaps_pte_entry(pte_t *pte, unsigned long addr,
                struct mm_walk *walk)
 {
-- 
 Kirill A. Shutemov

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