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    SubjectRe: md: raid10: fix use-after-free of bio
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    Am Samstag, den 28.07.2007, 23:55 -0700 schrieb Andrew Morton:
    > On Fri, 27 Jul 2007 16:46:23 +0200 Maik Hampel <m.hampel@gmx.de> wrote:
    >
    > > In case of read errors raid10d tries to print a nice error message,
    > > unfortunately using data from an already put bio.
    > >
    > > Signed-off-by: Maik Hampel <m.hampel@gmx.de>
    > >
    > > diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
    > > index f730a14..ea1b3e3 100644
    > > --- a/drivers/md/raid10.c
    > > +++ b/drivers/md/raid10.c
    > > @@ -1557,7 +1557,6 @@ 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"
    > > @@ -1567,6 +1566,7 @@ static void raid10d(mddev_t *mddev)
    > > raid_end_bio_io(r10_bio);
    > > } 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"
    > >
    > >
    >
    > 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.
    > } 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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