From e1846cff2fe614d93a2f89461b5935678fd34bd9 Mon Sep 17 00:00:00 2001
From: Vladimir Oltean <vladimir.oltean@nxp.com>
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 <vladimir.oltean@nxp.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
---
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 9e28219b223df..faccfb3f01583 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 ca71b62a44dc3..20ceac81a2c2c 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 03b5e59d033e4..a9b26b3002be6 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 7b2bf9b1fe697..de26c992f8214 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;
--
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