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From:   Alexander Potapenko <glider@google.com>
Date:   Fri, 9 Mar 2018 11:49:43 +0100
Message-ID: <CAG_fn=XP6X5rqRVBameyU-F2UOc4hpbowUBNxZENf2ZHpMSmfQ@mail.gmail.com>
Subject: Re: [PATCH] mm/mempolicy: Avoid use uninitialized preferred_node
To:     Yisheng Xie <xieyisheng1@huawei.com>
Cc:     Andrew Morton <akpm@linux-foundation.org>,
        Linux Memory Management List <linux-mm@kvack.org>,
        Dmitriy Vyukov <dvyukov@google.com>,
        Vlastimil Babka <vbabka@suse.cz>,
        "mhocko@suse.com" <mhocko@suse.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
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On Fri, Mar 9, 2018 at 6:21 AM, Yisheng Xie <xieyisheng1@huawei.com> wrote:
> Alexander reported an use of uninitialized memory in __mpol_equal(),
> which is caused by incorrect use of preferred_node.
>
> When mempolicy in mode MPOL_PREFERRED with flags MPOL_F_LOCAL, it use
> numa_node_id() instead of preferred_node, however, __mpol_equeue() use
> preferred_node without check whether it is MPOL_F_LOCAL or not.
>
> Reported-by: Alexander Potapenko <glider@google.com>
> Signed-off-by: Yisheng Xie <xieyisheng1@huawei.com>
Tested-by: Alexander Potapenko <glider@google.com>

I confirm that the patch fixes the problem. Thanks for the quick turnaround=
!
Any idea which commit had introduced the bug in the first place?
> ---
>  mm/mempolicy.c | 3 +++
>  1 file changed, 3 insertions(+)
>
> diff --git a/mm/mempolicy.c b/mm/mempolicy.c
> index d879f1d..641545e 100644
> --- a/mm/mempolicy.c
> +++ b/mm/mempolicy.c
> @@ -2124,6 +2124,9 @@ bool __mpol_equal(struct mempolicy *a, struct mempo=
licy *b)
>         case MPOL_INTERLEAVE:
>                 return !!nodes_equal(a->v.nodes, b->v.nodes);
>         case MPOL_PREFERRED:
> +               /* a's flags is the same as b's */
> +               if (a->flags & MPOL_F_LOCAL)
> +                       return true;
>                 return a->v.preferred_node =3D=3D b->v.preferred_node;
>         default:
>                 BUG();
> --
> 1.8.3.1
>


--=20
Alexander Potapenko
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