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net/sched: act_mirred: add loop detection

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Commit 0f022d32c3 ("net/sched: Fix mirred deadlock on device recursion")
added code in the fast path, even when act_mirred is not used.

Prepare its revert by implementing loop detection in act_mirred.

Adds an array of device pointers in struct netdev_xmit.

tcf_mirred_is_act_redirect() can detect if the array
already contains the target device.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Kuniyuki Iwashima <kuniyu@google.com>
Reviewed-by: Toke Høiland-Jørgensen <toke@redhat.com>
Tested-by: Jamal Hadi Salim <jhs@mojatatu.com>
Acked-by: Jamal Hadi Salim <jhs@mojatatu.com>
Link: https://patch.msgid.link/20251014171907.3554413-4-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Eric Dumazet 2025-10-14 17:19:04 +00:00 committed by Jakub Kicinski
parent 5b2b7dec05
commit fe946a751d
2 changed files with 31 additions and 40 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

9
include/linux/netdevice_xmit.h
View File

@ -2,6 +2,12 @@
#ifndef _LINUX_NETDEVICE_XMIT_H #ifndef _LINUX_NETDEVICE_XMIT_H
#define _LINUX_NETDEVICE_XMIT_H #define _LINUX_NETDEVICE_XMIT_H
#if IS_ENABLED(CONFIG_NET_ACT_MIRRED)
#define MIRRED_NEST_LIMIT 4
#endif
struct net_device;
struct netdev_xmit { struct netdev_xmit {
u16 recursion; u16 recursion;
u8 more; u8 more;
@ -9,7 +15,8 @@ struct netdev_xmit {
u8 skip_txqueue; u8 skip_txqueue;
#endif #endif
#if IS_ENABLED(CONFIG_NET_ACT_MIRRED) #if IS_ENABLED(CONFIG_NET_ACT_MIRRED)
u8 sched_mirred_nest; u8 sched_mirred_nest;
struct net_device *sched_mirred_dev[MIRRED_NEST_LIMIT];
#endif #endif
#if IS_ENABLED(CONFIG_NF_DUP_NETDEV) #if IS_ENABLED(CONFIG_NF_DUP_NETDEV)
u8 nf_dup_skb_recursion; u8 nf_dup_skb_recursion;

62
net/sched/act_mirred.c
View File

@ -29,31 +29,6 @@
static LIST_HEAD(mirred_list); static LIST_HEAD(mirred_list);
static DEFINE_SPINLOCK(mirred_list_lock); static DEFINE_SPINLOCK(mirred_list_lock);
#define MIRRED_NEST_LIMIT 4
#ifndef CONFIG_PREEMPT_RT
static u8 tcf_mirred_nest_level_inc_return(void)
{
return __this_cpu_inc_return(softnet_data.xmit.sched_mirred_nest);
}
static void tcf_mirred_nest_level_dec(void)
{
__this_cpu_dec(softnet_data.xmit.sched_mirred_nest);
}
#else
static u8 tcf_mirred_nest_level_inc_return(void)
{
return current->net_xmit.sched_mirred_nest++;
}
static void tcf_mirred_nest_level_dec(void)
{
current->net_xmit.sched_mirred_nest--;
}
#endif
static bool tcf_mirred_is_act_redirect(int action) static bool tcf_mirred_is_act_redirect(int action)
{ {
return action == TCA_EGRESS_REDIR || action == TCA_INGRESS_REDIR; return action == TCA_EGRESS_REDIR || action == TCA_INGRESS_REDIR;
@ -439,44 +414,53 @@ TC_INDIRECT_SCOPE int tcf_mirred_act(struct sk_buff *skb,
{ {
struct tcf_mirred *m = to_mirred(a); struct tcf_mirred *m = to_mirred(a);
int retval = READ_ONCE(m->tcf_action); int retval = READ_ONCE(m->tcf_action);
unsigned int nest_level; struct netdev_xmit *xmit;
bool m_mac_header_xmit; bool m_mac_header_xmit;
struct net_device *dev; struct net_device *dev;
int m_eaction; int i, m_eaction;
u32 blockid; u32 blockid;
nest_level = tcf_mirred_nest_level_inc_return(); #ifdef CONFIG_PREEMPT_RT
if (unlikely(nest_level > MIRRED_NEST_LIMIT)) { xmit = &current->net_xmit;
#else
xmit = this_cpu_ptr(&softnet_data.xmit);
#endif
if (unlikely(xmit->sched_mirred_nest >= MIRRED_NEST_LIMIT)) {
net_warn_ratelimited("Packet exceeded mirred recursion limit on dev %s\n", net_warn_ratelimited("Packet exceeded mirred recursion limit on dev %s\n",
netdev_name(skb->dev)); netdev_name(skb->dev));
retval = TC_ACT_SHOT; return TC_ACT_SHOT;
goto dec_nest_level;
} }
tcf_lastuse_update(&m->tcf_tm); tcf_lastuse_update(&m->tcf_tm);
tcf_action_update_bstats(&m->common, skb); tcf_action_update_bstats(&m->common, skb);
blockid = READ_ONCE(m->tcfm_blockid); blockid = READ_ONCE(m->tcfm_blockid);
if (blockid) { if (blockid)
retval = tcf_blockcast(skb, m, blockid, res, retval); return tcf_blockcast(skb, m, blockid, res, retval);
goto dec_nest_level;
}
dev = rcu_dereference_bh(m->tcfm_dev); dev = rcu_dereference_bh(m->tcfm_dev);
if (unlikely(!dev)) { if (unlikely(!dev)) {
pr_notice_once("tc mirred: target device is gone\n"); pr_notice_once("tc mirred: target device is gone\n");
tcf_action_inc_overlimit_qstats(&m->common); tcf_action_inc_overlimit_qstats(&m->common);
goto dec_nest_level; return retval;
} }
for (i = 0; i < xmit->sched_mirred_nest; i++) {
if (xmit->sched_mirred_dev[i] != dev)
continue;
pr_notice_once("tc mirred: loop on device %s\n",
netdev_name(dev));
tcf_action_inc_overlimit_qstats(&m->common);
return retval;
}
xmit->sched_mirred_dev[xmit->sched_mirred_nest++] = dev;
m_mac_header_xmit = READ_ONCE(m->tcfm_mac_header_xmit); m_mac_header_xmit = READ_ONCE(m->tcfm_mac_header_xmit);
m_eaction = READ_ONCE(m->tcfm_eaction); m_eaction = READ_ONCE(m->tcfm_eaction);
retval = tcf_mirred_to_dev(skb, m, dev, m_mac_header_xmit, m_eaction, retval = tcf_mirred_to_dev(skb, m, dev, m_mac_header_xmit, m_eaction,
retval); retval);
xmit->sched_mirred_nest--;
dec_nest_level:
tcf_mirred_nest_level_dec();
return retval; return retval;
} }