From: Mike Snitzer snitzer@redhat.com
commit a4a8d286586d4b28c8517a51db8d86954aadc74b upstream.
dm-thin uses struct pool to hold the state of the pool. There may be multiple pool_c's pointing to a given pool, each pool_c represents a loaded target. pool_c's may be created and destroyed arbitrarily and the pool contains a reference count of pool_c's pointing to it.
Since commit 694cfe7f31db3 ("dm thin: Flush data device before committing metadata") a pointer to pool_c is passed to dm_pool_register_pre_commit_callback and this function stores it in pmd->pre_commit_context. If this pool_c is freed, but pool is not (because there is another pool_c referencing it), we end up in a situation where pmd->pre_commit_context structure points to freed pool_c. It causes a crash in metadata_pre_commit_callback.
Fix this by moving the dm_pool_register_pre_commit_callback() from pool_ctr() to pool_preresume(). This way the in-core thin-pool metadata is only ever armed with callback data whose lifetime matches the active thin-pool target.
In should be noted that this fix preserves the ability to load a thin-pool table that uses a different data block device (that contains the same data) -- though it is unclear if that capability is still useful and/or needed.
Fixes: 694cfe7f31db3 ("dm thin: Flush data device before committing metadata") Cc: stable@vger.kernel.org Reported-by: Zdenek Kabelac zkabelac@redhat.com Reported-by: Mikulas Patocka mpatocka@redhat.com Signed-off-by: Mike Snitzer snitzer@redhat.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- drivers/md/dm-thin.c | 7 +++---- 1 file changed, 3 insertions(+), 4 deletions(-)
--- a/drivers/md/dm-thin.c +++ b/drivers/md/dm-thin.c @@ -3408,10 +3408,6 @@ static int pool_ctr(struct dm_target *ti if (r) goto out_flags_changed;
- dm_pool_register_pre_commit_callback(pt->pool->pmd, - metadata_pre_commit_callback, - pt); - pt->callbacks.congested_fn = pool_is_congested; dm_table_add_target_callbacks(ti->table, &pt->callbacks);
@@ -3574,6 +3570,9 @@ static int pool_preresume(struct dm_targ if (r) return r;
+ dm_pool_register_pre_commit_callback(pool->pmd, + metadata_pre_commit_callback, pt); + r = maybe_resize_data_dev(ti, &need_commit1); if (r) return r;