From e1846cff2fe614d93a2f89461b5935678fd34bd9 Mon Sep 17 00:00:00 2001 From: Vladimir Oltean Date: Thu, 5 May 2022 02:54:59 +0300 Subject: net: mscc: ocelot: mark traps with a bool instead of keeping them in a list Since the blamed commit, VCAP filters can appear on more than one list. If their action is "trap", they are chained on ocelot->traps via filter->trap_list. This is in addition to their normal placement on the VCAP block->rules list head. Therefore, when we free a VCAP filter, we must remove it from all lists it is a member of, including ocelot->traps. There are at least 2 bugs which are direct consequences of this design decision. First is the incorrect usage of list_empty(), meant to denote whether "filter" is chained into ocelot->traps via filter->trap_list. This does not do the correct thing, because list_empty() checks whether "head->next == head", but in our case, head->next == head->prev == NULL. So we dereference NULL pointers and die when we call list_del(). Second is the fact that not all places that should remove the filter from ocelot->traps do so. One example is ocelot_vcap_block_remove_filter(), which is where we have the main kfree(filter). By keeping freed filters in ocelot->traps we end up in a use-after-free in felix_update_trapping_destinations(). Attempting to fix all the buggy patterns is a whack-a-mole game which makes the driver unmaintainable. Actually this is what the previous patch version attempted to do: https://patchwork.kernel.org/project/netdevbpf/patch/20220503115728.834457-3-vladimir.oltean@nxp.com/ but it introduced another set of bugs, because there are other places in which create VCAP filters, not just ocelot_vcap_filter_create(): - ocelot_trap_add() - felix_tag_8021q_vlan_add_rx() - felix_tag_8021q_vlan_add_tx() Relying on the convention that all those code paths must call INIT_LIST_HEAD(&filter->trap_list) is not going to scale. So let's do what should have been done in the first place and keep a bool in struct ocelot_vcap_filter which denotes whether we are looking at a trapping rule or not. Iterating now happens over the main VCAP IS2 block->rules. The advantage is that we no longer risk having stale references to a freed filter, since it is only present in that list. Fixes: e42bd4ed09aa ("net: mscc: ocelot: keep traps in a list") Signed-off-by: Vladimir Oltean Signed-off-by: Jakub Kicinski --- drivers/net/dsa/ocelot/felix.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) (limited to 'drivers/net/dsa') diff --git a/drivers/net/dsa/ocelot/felix.c b/drivers/net/dsa/ocelot/felix.c index 9e28219b223d..faccfb3f0158 100644 --- a/drivers/net/dsa/ocelot/felix.c +++ b/drivers/net/dsa/ocelot/felix.c @@ -403,6 +403,7 @@ static int felix_update_trapping_destinations(struct dsa_switch *ds, { struct ocelot *ocelot = ds->priv; struct felix *felix = ocelot_to_felix(ocelot); + struct ocelot_vcap_block *block_vcap_is2; struct ocelot_vcap_filter *trap; enum ocelot_mask_mode mask_mode; unsigned long port_mask; @@ -422,9 +423,13 @@ static int felix_update_trapping_destinations(struct dsa_switch *ds, /* We are sure that "cpu" was found, otherwise * dsa_tree_setup_default_cpu() would have failed earlier. */ + block_vcap_is2 = &ocelot->block[VCAP_IS2]; /* Make sure all traps are set up for that destination */ - list_for_each_entry(trap, &ocelot->traps, trap_list) { + list_for_each_entry(trap, &block_vcap_is2->rules, list) { + if (!trap->is_trap) + continue; + /* Figure out the current trapping destination */ if (using_tag_8021q) { /* Redirect to the tag_8021q CPU port. If timestamps -- cgit