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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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