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    SubjectRe: [PATCH 1/1] swapfile: swap_info_get: Check for swap_info[type] == NULL
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    Hi,

    Sorry, please ignore the patch file below.

    I made a mistake in understanding the code logic.
    I now understand that the first "bad_nofile" validation check
    is good enough for checking the validity of the value in the "type" variable.


    On Mon, Dec 26, 2011 at 6:56 AM, Kautuk Consul <consul.kautuk@gmail.com> wrote:
    > From: Kautuk Consul <consul.kautuk@gmail.com>
    >
    > If the swapfile type encoded within entry.val is corrupted in
    > such a way that the swap_info[type] == NULL, then the code in
    > swap_info_get will cause a NULL pointer exception.
    >
    > Assuming that the code in swap_info_get attempts to validate the
    > swapfile type by checking its range, another bad_nofile check would
    > be to check for check whether the swap_info[type] pointer is NULL.
    >
    > Adding a NULL check for swap_info[type] to be reagrded as a "bad_nofile"
    > error scenario.
    >
    > Signed-off-by: Kautuk Consul <consul.kautuk@gmail.com>
    > ---
    >  mm/swapfile.c |    2 ++
    >  1 files changed, 2 insertions(+), 0 deletions(-)
    >
    > diff --git a/mm/swapfile.c b/mm/swapfile.c
    > index b1cd120..7bdbe91 100644
    > --- a/mm/swapfile.c
    > +++ b/mm/swapfile.c
    > @@ -483,6 +483,8 @@ static struct swap_info_struct *swap_info_get(swp_entry_t entry)
    >        if (type >= nr_swapfiles)
    >                goto bad_nofile;
    >        p = swap_info[type];
    > +       if (!p)
    > +               goto bad_nofile;
    >        if (!(p->flags & SWP_USED))
    >                goto bad_device;
    >        offset = swp_offset(entry);
    > --
    > 1.7.6
    >
    --
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