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    SubjectRe: [PATCH] fix read past end of array in md/linear.c
    On Thu, Mar 08, 2007 at 12:52:04PM -0800, Andy Isaacson wrote:
    > When iterating through an array, one must be careful to test one's index
    > variable rather than another similarly-named variable.
    >
    > The loop will read off the end of conf->disks[] in the following
    > (pathological) case:
    >
    > % dd bs=1 seek=840716287 if=/dev/zero of=d1 count=1
    > % for i in 2 3 4; do dd if=/dev/zero of=d$i bs=1k count=$(($i+150)); done
    > % ./vmlinux ubd0=root ubd1=d1 ubd2=d2 ubd3=d3 ubd4=d4
    > # mdadm -C /dev/md0 --level=linear --raid-devices=4 /dev/ubd[1234]
    >
    > adding some printks, I saw this:
    > [42949374.960000] hash_spacing = 821120
    > [42949374.960000] cnt = 4
    > [42949374.960000] min_spacing = 801
    > [42949374.960000] j=0 size=820928 sz=820928
    > [42949374.960000] i=0 sz=820928 hash_spacing=820928
    > [42949374.960000] j=1 size=64 sz=64
    > [42949374.960000] j=2 size=64 sz=128
    > [42949374.960000] j=3 size=64 sz=192
    > [42949374.960000] j=4 size=1515870810 sz=1515871002
    >
    > Index: linus/drivers/md/linear.c
    > ===================================================================
    > --- linus.orig/drivers/md/linear.c 2007-03-02 11:35:55.000000000 -0800
    > +++ linus/drivers/md/linear.c 2007-03-07 13:10:30.000000000 -0800
    > @@ -188,7 +188,7 @@
    > for (i=0; i < cnt-1 ; i++) {
    > sector_t sz = 0;
    > int j;
    > - for (j=i; i<cnt-1 && sz < min_spacing ; j++)
    > + for (j=i; j<cnt-1 && sz < min_spacing ; j++)
    > sz += conf->disks[j].size;
    > if (sz >= min_spacing && sz < conf->hash_spacing)
    > conf->hash_spacing = sz;

    Forgot to add:

    Signed-off-by: Andrew Isaacson <adi@hexapodia.org>

    -andy
    -
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