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    SubjectRe: [PATCH] mm: fix null pointer dereference in wait_iff_congested()
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    Just FYI:

    This patch landed upstream [1].
    Thanks for all involved people.

    - Sedat -

    [1] http://git.kernel.org/?p=linux/kernel/git/torvalds/linux.git;a=commitdiff;h=ecccd1248d6e6986130ffcc3b0d003cb46a485c0

    On Fri, Dec 28, 2012 at 3:16 AM, Zlatko Calusic <zlatko.calusic@iskon.hr> wrote:
    > From: Zlatko Calusic <zlatko.calusic@iskon.hr>
    >
    > The unintended consequence of commit 4ae0a48b is that
    > wait_iff_congested() can now be called with NULL struct zone*
    > producing kernel oops like this:
    >
    > BUG: unable to handle kernel NULL pointer dereference
    > IP: [<ffffffff811542d9>] wait_iff_congested+0x59/0x140
    >
    > This trivial patch fixes it.
    >
    > Reported-by: Zhouping Liu <zliu@redhat.com>
    > Reported-and-tested-by: Sedat Dilek <sedat.dilek@gmail.com>
    > Cc: Andrew Morton <akpm@linux-foundation.org>
    > Cc: Mel Gorman <mgorman@suse.de>
    > Cc: Hugh Dickins <hughd@google.com>
    > Signed-off-by: Zlatko Calusic <zlatko.calusic@iskon.hr>
    > ---
    > mm/vmscan.c | 2 +-
    > 1 file changed, 1 insertion(+), 1 deletion(-)
    >
    > diff --git a/mm/vmscan.c b/mm/vmscan.c
    > index 02bcfa3..e55ce55 100644
    > --- a/mm/vmscan.c
    > +++ b/mm/vmscan.c
    > @@ -2782,7 +2782,7 @@ loop_again:
    > if (total_scanned && (sc.priority < DEF_PRIORITY - 2)) {
    > if (has_under_min_watermark_zone)
    > count_vm_event(KSWAPD_SKIP_CONGESTION_WAIT);
    > - else
    > + else if (unbalanced_zone)
    > wait_iff_congested(unbalanced_zone, BLK_RW_ASYNC, HZ/10);
    > }
    >
    > --
    > 1.8.1.rc3
    >
    > --
    > Zlatko


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