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    SubjectRe: md: raid10: fix use-after-free of bio
    On Monday July 30, m.hampel@gmx.de wrote:
    > >
    > > Surely we just leaked that bio if (mirror == -1)?
    > >
    > > better:
    > >
    > > --- a/drivers/md/raid10.c~md-raid10-fix-use-after-free-of-bio
    > > +++ a/drivers/md/raid10.c
    > > @@ -1534,7 +1534,6 @@ static void raid10d(mddev_t *mddev)
    > > bio = r10_bio->devs[r10_bio->read_slot].bio;
    > > r10_bio->devs[r10_bio->read_slot].bio =
    > > mddev->ro ? IO_BLOCKED : NULL;
    > > - bio_put(bio);
    > > mirror = read_balance(conf, r10_bio);
    > > if (mirror == -1) {
    > > printk(KERN_ALERT "raid10: %s: unrecoverable I/O"
    > > @@ -1542,8 +1541,10 @@ static void raid10d(mddev_t *mddev)
    > > bdevname(bio->bi_bdev,b),
    > > (unsigned long long)r10_bio->sector);
    > > raid_end_bio_io(r10_bio);
    > > + bio_put(bio);
    > raid_end_bio_io() calls put_all_bios(), which does a bio_put() to
    > corresponding r10_bio->devs[i]. So this looks like redundant code for
    > me.

    Yes, but note above that this bio for this slot has been set to
    'NULL', so put_all_bios won't find anything to call bio_put on.

    Thanks,
    NeilBrown


    > > } else {
    > > const int do_sync = bio_sync(r10_bio->master_bio);
    > > + bio_put(bio);
    > > rdev = conf->mirrors[mirror].rdev;
    > > if (printk_ratelimit())
    > > printk(KERN_ERR "raid10: %s: redirecting sector %llu to"
    >
    > Regards,
    > Maik Hampel
    >
    -
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