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drbd: fix possible access after free

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If we release the page pointed to by md_io_tmpp, we need to zero out the
pointer, too, as that may be used later to decide whether we need to
allocate a new page again.

Impact: a previously freed page may be used and clobbered.  Depending on
what that particular page is being used for meanwhile, this may result
in silent data corruption of completely unrelated things.

Only of concern on devices with logical_block_size != 512 byte,
if you re-attach after becoming diskless once.

Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>
This commit is contained in:
Lars Ellenberg 2010-09-14 20:14:09 +02:00 committed by Philipp Reisner
parent 8979d9c9e0
commit f65363cfa0
1 changed files with 3 additions and 1 deletions
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4
drivers/block/drbd/drbd_main.c
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@ -1407,8 +1407,10 @@ static void after_state_ch(struct drbd_conf *mdev, union drbd_state os,
drbd_free_bc(mdev->ldev); drbd_free_bc(mdev->ldev);
mdev->ldev = NULL;); mdev->ldev = NULL;);
if (mdev->md_io_tmpp) if (mdev->md_io_tmpp) {
__free_page(mdev->md_io_tmpp); __free_page(mdev->md_io_tmpp);
mdev->md_io_tmpp = NULL;
}
} }
/* Disks got bigger while they were detached */ /* Disks got bigger while they were detached */