diff options
| author | Lars Ellenberg | 2012-06-19 09:40:00 +0200 |
|---|---|---|
| committer | Philipp Reisner | 2012-07-24 14:15:16 +0200 |
| commit | c12e9c8964215aaf2b5dcd06048444c2b672f0b9 (patch) | |
| tree | a13c5561ad0325ca247f4c1d9d0b7770da0c64bb /drivers/block | |
| parent | 63a6d0bb3dd69afedb2b2952eb1d1e8340c11d0d (diff) | |
drbd: fix potential access after free
Occasionally, if we disconnect, we triggered this assert:
block drbd7: ASSERT FAILED tl_hash[27] == c30b0f04, expected NULL
hlist_del() happens only on master bio completion.
We used to wait for pending IO to complete before freeing tl_hash
on disconnect. We no longer do so, since we learned to "freeze"
IO on disconnect.
If the local disk is too slow, we may reach C_STANDALONE early,
and there are still some requests pending locally when we call
drbd_free_tl_hash().
If we now free the tl_hash, and later the local IO completion completes
the master bio, which then does hlist_del() and clobbers freed memory.
Do hlist_del_init() and hlist_add_fake() before kfree(tl_hash),
so the hlist_del() on master bio completion is harmless.
Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>
Diffstat (limited to 'drivers/block')
| -rw-r--r-- | drivers/block/drbd/drbd_receiver.c | 17 |
1 files changed, 12 insertions, 5 deletions
diff --git a/drivers/block/drbd/drbd_receiver.c b/drivers/block/drbd/drbd_receiver.c index ea4836e0ae98..83d99133f94b 100644 --- a/drivers/block/drbd/drbd_receiver.c +++ b/drivers/block/drbd/drbd_receiver.c @@ -3801,11 +3801,18 @@ void drbd_free_tl_hash(struct drbd_conf *mdev) mdev->ee_hash = NULL; mdev->ee_hash_s = 0; - /* paranoia code */ - for (h = mdev->tl_hash; h < mdev->tl_hash + mdev->tl_hash_s; h++) - if (h->first) - dev_err(DEV, "ASSERT FAILED tl_hash[%u] == %p, expected NULL\n", - (int)(h - mdev->tl_hash), h->first); + /* We may not have had the chance to wait for all locally pending + * application requests. The hlist_add_fake() prevents access after + * free on master bio completion. */ + for (h = mdev->tl_hash; h < mdev->tl_hash + mdev->tl_hash_s; h++) { + struct drbd_request *req; + struct hlist_node *pos, *n; + hlist_for_each_entry_safe(req, pos, n, h, collision) { + hlist_del_init(&req->collision); + hlist_add_fake(&req->collision); + } + } + kfree(mdev->tl_hash); mdev->tl_hash = NULL; mdev->tl_hash_s = 0; |