| From | Greg Kroah-Hartman <> | Subject | [PATCH 4.9 047/105] net: sched: fix use-after-free in tcf_action_destroy and tcf_del_walker | Date | Tue, 10 Oct 2017 21:50:18 +0200 |
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4.9-stable review patch. If anyone has any objections, please let me know.
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From: Jiri Pirko <jiri@mellanox.com>
[ Upstream commit 255cd50f207ae8ec7b22663246c833407744e634 ]
Recent commit d7fb60b9cafb ("net_sched: get rid of tcfa_rcu") removed freeing in call_rcu, which changed already existing hard-to-hit race condition into 100% hit:
[ 598.599825] BUG: unable to handle kernel NULL pointer dereference at 0000000000000030 [ 598.607782] IP: tcf_action_destroy+0xc0/0x140
Or:
[ 40.858924] BUG: unable to handle kernel NULL pointer dereference at 0000000000000030 [ 40.862840] IP: tcf_generic_walker+0x534/0x820
Fix this by storing the ops and use them directly for module_put call.
Fixes: a85a970af265 ("net_sched: move tc_action into tcf_common") Signed-off-by: Jiri Pirko <jiri@mellanox.com> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> --- net/sched/act_api.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-)
--- a/net/sched/act_api.c +++ b/net/sched/act_api.c @@ -141,7 +141,7 @@ static int tcf_del_walker(struct tcf_has hlist_for_each_entry_safe(p, n, head, tcfa_head) { ret = __tcf_hash_release(p, false, true); if (ret == ACT_P_DELETED) { - module_put(p->ops->owner); + module_put(ops->owner); n_i++; } else if (ret < 0) goto nla_put_failure; @@ -450,13 +450,15 @@ EXPORT_SYMBOL(tcf_action_exec); int tcf_action_destroy(struct list_head *actions, int bind) { + const struct tc_action_ops *ops; struct tc_action *a, *tmp; int ret = 0; list_for_each_entry_safe(a, tmp, actions, list) { + ops = a->ops; ret = __tcf_hash_release(a, bind, true); if (ret == ACT_P_DELETED) - module_put(a->ops->owner); + module_put(ops->owner); else if (ret < 0) return ret; }
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