From: Zhiqiang Liu liuzhiqiang26@huawei.com
hulk inclusion category: bugfix bugzilla: 13690 CVE: CVE-2020-12771
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coccicheck reports: drivers/md//bcache/btree.c:1538:1-7: preceding lock on line 1417
btree_gc_coalesce func is designed to coalesce two adjacent nodes in new_nodes[GC_MERGE_NODES] and finally release one node. All nodes`write_lock, new_nodes[i]->write_lock, are holded before coalescing adjacent nodes, and them will be released after coalescing successfully.
However, if the coalescing process fails, such as no enough space of new_nodes[1] to fit all of the remaining keys in new_nodes[0] and realloc keylist failed, we will goto to out_nocoalesce tag directly without releasing new_nodes[i]->write_lock. Then, a deadlock will occur after calling btree_node_free to free new_nodes[i], which also try to acquire new_nodes[i]->write_lock.
Here, we add a new tag 'out_unlock_nocoalesce' before out_nocoalesce tag to release new_nodes[i]->write_lock when coalescing process fails.
Fixes: 2a285686c1 ("bcache: btree locking rework") Signed-off-by: Zhiqiang Liu liuzhiqiang26@huawei.com Signed-off-by: Yang Yingliang yangyingliang@huawei.com Reviewed-by: Jason Yan yanaijie@huawei.com Signed-off-by: Yang Yingliang yangyingliang@huawei.com --- drivers/md/bcache/btree.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-)
diff --git a/drivers/md/bcache/btree.c b/drivers/md/bcache/btree.c index 74c5267..2298028 100644 --- a/drivers/md/bcache/btree.c +++ b/drivers/md/bcache/btree.c @@ -1450,7 +1450,7 @@ static int btree_gc_coalesce(struct btree *b, struct btree_op *op, if (__set_blocks(n1, n1->keys + n2->keys, block_bytes(b->c)) > btree_blocks(new_nodes[i])) - goto out_nocoalesce; + goto out_unlock_nocoalesce;
keys = n2->keys; /* Take the key of the node we're getting rid of */ @@ -1479,7 +1479,7 @@ static int btree_gc_coalesce(struct btree *b, struct btree_op *op,
if (__bch_keylist_realloc(&keylist, bkey_u64s(&new_nodes[i]->key))) - goto out_nocoalesce; + goto out_unlock_nocoalesce;
bch_btree_node_write(new_nodes[i], &cl); bch_keylist_add(&keylist, &new_nodes[i]->key); @@ -1525,6 +1525,10 @@ static int btree_gc_coalesce(struct btree *b, struct btree_op *op, /* Invalidated our iterator */ return -EINTR;
+out_unlock_nocoalesce: + for (i = 0; i < nodes; i++) + mutex_unlock(&new_nodes[i]->write_lock); + out_nocoalesce: closure_sync(&cl);