From e1846cff2fe614d93a2f89461b5935678fd34bd9 Mon Sep 17 00:00:00 2001 From: Vladimir Oltean Date: Thu, 5 May 2022 02:54:59 +0300 Subject: [PATCH] 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 ++++++- drivers/net/ethernet/mscc/ocelot.c | 11 +++-------- drivers/net/ethernet/mscc/ocelot_flower.c | 4 +--- include/soc/mscc/ocelot_vcap.h | 2 +- 4 files changed, 11 insertions(+), 13 deletions(-) diff --git a/drivers/net/dsa/ocelot/felix.c b/drivers/net/dsa/ocelot/felix.c index 9e28219..faccfb3 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 diff --git a/drivers/net/ethernet/mscc/ocelot.c b/drivers/net/ethernet/mscc/ocelot.c index ca71b62..20ceac8 100644 --- a/drivers/net/ethernet/mscc/ocelot.c +++ b/drivers/net/ethernet/mscc/ocelot.c @@ -1622,7 +1622,7 @@ int ocelot_trap_add(struct ocelot *ocelot, int port, trap->action.mask_mode = OCELOT_MASK_MODE_PERMIT_DENY; trap->action.port_mask = 0; trap->take_ts = take_ts; - list_add_tail(&trap->trap_list, &ocelot->traps); + trap->is_trap = true; new = true; } @@ -1634,10 +1634,8 @@ int ocelot_trap_add(struct ocelot *ocelot, int port, err = ocelot_vcap_filter_replace(ocelot, trap); if (err) { trap->ingress_port_mask &= ~BIT(port); - if (!trap->ingress_port_mask) { - list_del(&trap->trap_list); + if (!trap->ingress_port_mask) kfree(trap); - } return err; } @@ -1657,11 +1655,8 @@ int ocelot_trap_del(struct ocelot *ocelot, int port, unsigned long cookie) return 0; trap->ingress_port_mask &= ~BIT(port); - if (!trap->ingress_port_mask) { - list_del(&trap->trap_list); - + if (!trap->ingress_port_mask) return ocelot_vcap_filter_del(ocelot, trap); - } return ocelot_vcap_filter_replace(ocelot, trap); } diff --git a/drivers/net/ethernet/mscc/ocelot_flower.c b/drivers/net/ethernet/mscc/ocelot_flower.c index 03b5e59..a9b26b3 100644 --- a/drivers/net/ethernet/mscc/ocelot_flower.c +++ b/drivers/net/ethernet/mscc/ocelot_flower.c @@ -295,7 +295,7 @@ static int ocelot_flower_parse_action(struct ocelot *ocelot, int port, filter->action.cpu_copy_ena = true; filter->action.cpu_qu_num = 0; filter->type = OCELOT_VCAP_FILTER_OFFLOAD; - list_add_tail(&filter->trap_list, &ocelot->traps); + filter->is_trap = true; break; case FLOW_ACTION_POLICE: if (filter->block_id == PSFP_BLOCK_ID) { @@ -878,8 +878,6 @@ int ocelot_cls_flower_replace(struct ocelot *ocelot, int port, ret = ocelot_flower_parse(ocelot, port, ingress, f, filter); if (ret) { - if (!list_empty(&filter->trap_list)) - list_del(&filter->trap_list); kfree(filter); return ret; } diff --git a/include/soc/mscc/ocelot_vcap.h b/include/soc/mscc/ocelot_vcap.h index 7b2bf9b..de26c99 100644 --- a/include/soc/mscc/ocelot_vcap.h +++ b/include/soc/mscc/ocelot_vcap.h @@ -681,7 +681,6 @@ struct ocelot_vcap_id { struct ocelot_vcap_filter { struct list_head list; - struct list_head trap_list; enum ocelot_vcap_filter_type type; int block_id; @@ -695,6 +694,7 @@ struct ocelot_vcap_filter { struct ocelot_vcap_stats stats; /* For VCAP IS1 and IS2 */ bool take_ts; + bool is_trap; unsigned long ingress_port_mask; /* For VCAP ES0 */ struct ocelot_vcap_port ingress_port; -- 2.7.4