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    Subject[PATCH 3.18 098/185] mm/mempolicy.c: avoid use uninitialized preferred_node
    Date
    3.18-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Yisheng Xie <xieyisheng1@huawei.com>

    [ Upstream commit 8970a63e965b43288c4f5f40efbc2bbf80de7f16 ]

    Alexander reported a 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 uses
    numa_node_id() instead of preferred_node, however, __mpol_equal() uses
    preferred_node without checking whether it is MPOL_F_LOCAL or not.

    [akpm@linux-foundation.org: slight comment tweak]
    Link: http://lkml.kernel.org/r/4ebee1c2-57f6-bcb8-0e2d-1833d1ee0bb7@huawei.com
    Fixes: fc36b8d3d819 ("mempolicy: use MPOL_F_LOCAL to Indicate Preferred Local Policy")
    Signed-off-by: Yisheng Xie <xieyisheng1@huawei.com>
    Reported-by: Alexander Potapenko <glider@google.com>
    Tested-by: Alexander Potapenko <glider@google.com>
    Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
    Cc: Dmitriy Vyukov <dvyukov@google.com>
    Cc: Vlastimil Babka <vbabka@suse.cz>
    Cc: Michal Hocko <mhocko@kernel.org>
    Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
    Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
    Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    mm/mempolicy.c | 3 +++
    1 file changed, 3 insertions(+)

    --- a/mm/mempolicy.c
    +++ b/mm/mempolicy.c
    @@ -2169,6 +2169,9 @@ bool __mpol_equal(struct mempolicy *a, s
    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 == b->v.preferred_node;
    default:
    BUG();

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