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    SubjectRe: [PATCH 1/5] tmpfs: fix oops on mounts with mpol=default
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    On Tue, 2010-03-16 at 14:49 +0900, KOSAKI Motohiro wrote:
    > ChangeLog from Ravikiran's original one
    > - Fix the patch description. the problem is in mount, not only remount.
    > - Skip mpol_new() simply, instead adding NULL check.
    >
    >
    > =========================
    > From: Ravikiran G Thirumalai <kiran@scalex86.org>
    >
    > Fix an 'oops' when a tmpfs mount point is mounted with the mpol=default
    > mempolicy.
    >
    > Upon remounting a tmpfs mount point with 'mpol=default' option, the
    > mount code crashed with a null pointer dereference. The initial
    > problem report was on 2.6.27, but the problem exists in mainline
    > 2.6.34-rc as well. On examining the code, we see that mpol_new returns
    > NULL if default mempolicy was requested. This 'NULL' mempolicy is
    > accessed to store the node mask resulting in oops.
    >
    > The following patch fixes it.
    >
    > Signed-off-by: Ravikiran Thirumalai <kiran@scalex86.org>
    > Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
    > Cc: Christoph Lameter <cl@linux-foundation.org>
    > Cc: Mel Gorman <mel@csn.ul.ie>
    > Cc: Lee Schermerhorn <lee.schermerhorn@hp.com>
    > Cc: Hugh Dickins <hugh.dickins@tiscali.co.uk>
    > Cc: <stable@kernel.org>

    Acked-by: Lee Schermerhorn <lee.schermerhorn@hp.com>

    > ---
    > mm/mempolicy.c | 9 +++++++--
    > 1 files changed, 7 insertions(+), 2 deletions(-)
    >
    > diff --git a/mm/mempolicy.c b/mm/mempolicy.c
    > index bda230e..25a0c0f 100644
    > --- a/mm/mempolicy.c
    > +++ b/mm/mempolicy.c
    > @@ -2213,10 +2213,15 @@ int mpol_parse_str(char *str, struct mempolicy **mpol, int no_context)
    > goto out;
    > mode = MPOL_PREFERRED;
    > break;
    > -
    > + case MPOL_DEFAULT:
    > + /*
    > + * Insist on a empty nodelist
    > + */
    > + if (!nodelist)
    > + err = 0;
    > + goto out;
    > /*
    > * case MPOL_BIND: mpol_new() enforces non-empty nodemask.
    > - * case MPOL_DEFAULT: mpol_new() enforces empty nodemask, ignores flags.
    > */
    > }
    >



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