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authorTaehee Yoo <ap420073@gmail.com>2023-09-05 08:46:10 +0000
committerDavid S. Miller <davem@davemloft.net>2023-09-06 06:04:13 +0100
commit39285e124edbc752331e98ace37cc141a6a3747a (patch)
tree418de278d1a3be2520173d365cfc14db6060daea /include
parenta5e2151ff9d5852d0ababbbcaeebd9646af9c8d9 (diff)
net: team: do not use dynamic lockdep key
team interface has used a dynamic lockdep key to avoid false-positive lockdep deadlock detection. Virtual interfaces such as team usually have their own lock for protecting private data. These interfaces can be nested. team0 | team1 Each interface's lock is actually different(team0->lock and team1->lock). So, mutex_lock(&team0->lock); mutex_lock(&team1->lock); mutex_unlock(&team1->lock); mutex_unlock(&team0->lock); The above case is absolutely safe. But lockdep warns about deadlock. Because the lockdep understands these two locks are same. This is a false-positive lockdep warning. So, in order to avoid this problem, the team interfaces started to use dynamic lockdep key. The false-positive problem was fixed, but it introduced a new problem. When the new team virtual interface is created, it registers a dynamic lockdep key(creates dynamic lockdep key) and uses it. But there is the limitation of the number of lockdep keys. So, If so many team interfaces are created, it consumes all lockdep keys. Then, the lockdep stops to work and warns about it. In order to fix this problem, team interfaces use the subclass instead of the dynamic key. So, when a new team interface is created, it doesn't register(create) a new lockdep, but uses existed subclass key instead. It is already used by the bonding interface for a similar case. As the bonding interface does, the subclass variable is the same as the 'dev->nested_level'. This variable indicates the depth in the stacked interface graph. The 'dev->nested_level' is protected by RTNL and RCU. So, 'mutex_lock_nested()' for 'team->lock' requires RTNL or RCU. In the current code, 'team->lock' is usually acquired under RTNL, there is no problem with using 'dev->nested_level'. The 'team_nl_team_get()' and The 'lb_stats_refresh()' functions acquire 'team->lock' without RTNL. But these don't iterate their own ports nested so they don't need nested lock. Reproducer: for i in {0..1000} do ip link add team$i type team ip link add dummy$i master team$i type dummy ip link set dummy$i up ip link set team$i up done Splat looks like: BUG: MAX_LOCKDEP_ENTRIES too low! turning off the locking correctness validator. Please attach the output of /proc/lock_stat to the bug report CPU: 0 PID: 4104 Comm: ip Not tainted 6.5.0-rc7+ #45 Call Trace: <TASK> dump_stack_lvl+0x64/0xb0 add_lock_to_list+0x30d/0x5e0 check_prev_add+0x73a/0x23a0 ... sock_def_readable+0xfe/0x4f0 netlink_broadcast+0x76b/0xac0 nlmsg_notify+0x69/0x1d0 dev_open+0xed/0x130 ... Reported-by: syzbot+9bbbacfbf1e04d5221f7@syzkaller.appspotmail.com Fixes: 369f61bee0f5 ("team: fix nested locking lockdep warning") Signed-off-by: Taehee Yoo <ap420073@gmail.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'include')
-rw-r--r--include/linux/if_team.h30
1 files changed, 29 insertions, 1 deletions
diff --git a/include/linux/if_team.h b/include/linux/if_team.h
index 1b9b15a492fa..12d4447fc8ab 100644
--- a/include/linux/if_team.h
+++ b/include/linux/if_team.h
@@ -221,10 +221,38 @@ struct team {
atomic_t count_pending;
struct delayed_work dw;
} mcast_rejoin;
- struct lock_class_key team_lock_key;
long mode_priv[TEAM_MODE_PRIV_LONGS];
};
+static inline void __team_lock(struct team *team)
+{
+ mutex_lock(&team->lock);
+}
+
+static inline int team_trylock(struct team *team)
+{
+ return mutex_trylock(&team->lock);
+}
+
+#ifdef CONFIG_LOCKDEP
+static inline void team_lock(struct team *team)
+{
+ ASSERT_RTNL();
+ mutex_lock_nested(&team->lock, team->dev->nested_level);
+}
+
+#else
+static inline void team_lock(struct team *team)
+{
+ __team_lock(team);
+}
+#endif
+
+static inline void team_unlock(struct team *team)
+{
+ mutex_unlock(&team->lock);
+}
+
static inline int team_dev_queue_xmit(struct team *team, struct team_port *port,
struct sk_buff *skb)
{