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    Subject[39/45] tmpfs: fix oops on mounts with mpol=default
    2.6.27-stable review patch.  If anyone has any objections, please let us know.

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

    From: Ravikiran G Thirumalai <kiran@scalex86.org>

    commit 413b43deab8377819aba1dbad2abf0c15d59b491 upstream.

    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>
    Acked-by: Lee Schermerhorn <lee.schermerhorn@hp.com>
    Cc: Hugh Dickins <hugh.dickins@tiscali.co.uk>
    Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
    Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
    Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

    ---
    mm/mempolicy.c | 9 +++++++--
    1 file changed, 7 insertions(+), 2 deletions(-)

    --- a/mm/mempolicy.c
    +++ b/mm/mempolicy.c
    @@ -2049,10 +2049,15 @@ int mpol_parse_str(char *str, struct mem
    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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