CVE-2022-49808 Information

Description

In the Linux kernel the following vulnerability has been resolved:

net: dsa: don’t leak tagger-owned storage on switch driver unbind

In the initial commit dc452a471dba ( et: dsa: introduce tagger-owned storage for private and shared data) we had a call to tag_ops->disconnect(dst) issued from dsa_tree_free() which is called at tree teardown time.

There were problems with connecting to a switch tree as a whole so this got reworked to connecting to individual switches within the tree. In this process tag_ops->disconnect(ds) was made to be called only from switch.c (cross-chip notifiers emitted as a result of dynamic tag proto changes) but the normal driver teardown code path wasn’t replaced with anything.

Solve this problem by adding a function that does the opposite of dsa_switch_setup_tag_protocol() which is called from the equivalent spot in dsa_switch_teardown(). The positioning here also ensures that we won’t have any use-after-free in tagging protocol (rcv) ops since the teardown sequence is as follows:

dsa_tree_teardown -> dsa_tree_teardown_master -> dsa_master_teardown -> unsets master->dsa_ptr making no further packets match the ETH_P_XDSA packet type handler -> dsa_tree_teardown_ports -> dsa_port_teardown -> dsa_slave_destroy -> unregisters DSA net devices there is even a synchronize_net() in unregister_netdevice_many() -> dsa_tree_teardown_switches -> dsa_switch_teardown -> dsa_switch_teardown_tag_protocol -> finally frees the tagger-owned storage

Reference

https://git.kernel.org/stable/c/4e0c19fcb8b5323716140fa82b79aa9f60e60407 https://git.kernel.org/stable/c/5809fb03942dbac25144db5bebea84fa003ecaca