syzbot reports for sleeping function called from invalid context [1]. The recently added code for resizable hash tables uses hlist_bl bit locks in combination with spin_lock for the connection fields (cp->lock). Fix the following problems: * avoid using spin_lock(&cp->lock) under locked bit lock because it sleeps on PREEMPT_RT * as the recent changes call ip_vs_conn_hash() only for newly allocated connection, the spin_lock can be removed there because the connection is still not linked to table and does not need cp->lock protection. * the lock can be removed also from ip_vs_conn_unlink() where we are the last connection user. * the last place that is fixed is ip_vs_conn_fill_cport() where the locks can be reordered to follow the RT rules. [1]: BUG: sleeping function called from invalid context at kernel/locking/spinlock_rt.c:48 in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 16, name: ktimers/0 preempt_count: 2, expected: 0 RCU nest depth: 3, expected: 3 8 locks held by ktimers/0/16: #0: ffffffff8de5f260 (local_bh){.+.+}-{1:3}, at: __local_bh_disable_ip+0x3c/0x420 kernel/softirq.c:163 #1: ffffffff8dfc80c0 (rcu_read_lock){....}-{1:3}, at: __local_bh_disable_ip+0x3c/0x420 kernel/softirq.c:163 #2: ffff8880b8826360 (&base->expiry_lock){+...}-{3:3}, at: spin_lock include/linux/spinlock_rt.h:45 [inline] #2: ffff8880b8826360 (&base->expiry_lock){+...}-{3:3}, at: timer_base_lock_expiry kernel/time/timer.c:1502 [inline] #2: ffff8880b8826360 (&base->expiry_lock){+...}-{3:3}, at: __run_timer_base+0x120/0x9f0 kernel/time/timer.c:2384 #3: ffffffff8dfc80c0 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:300 [inline] #3: ffffffff8dfc80c0 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:838 [inline] #3: ffffffff8dfc80c0 (rcu_read_lock){....}-{1:3}, at: __rt_spin_lock kernel/locking/spinlock_rt.c:50 [inline] #3: ffffffff8dfc80c0 (rcu_read_lock){....}-{1:3}, at: rt_spin_lock+0x1e0/0x400 kernel/locking/spinlock_rt.c:57 #4: ffffc90000157a80 ((&cp->timer)){+...}-{0:0}, at: call_timer_fn+0xd4/0x5e0 kernel/time/timer.c:1745 #5: ffffffff8dfc80c0 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:300 [inline] #5: ffffffff8dfc80c0 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:838 [inline] #5: ffffffff8dfc80c0 (rcu_read_lock){....}-{1:3}, at: ip_vs_conn_unlink net/netfilter/ipvs/ip_vs_conn.c:315 [inline] #5: ffffffff8dfc80c0 (rcu_read_lock){....}-{1:3}, at: ip_vs_conn_expire+0x257/0x2390 net/netfilter/ipvs/ip_vs_conn.c:1260 #6: ffffffff8de5f260 (local_bh){.+.+}-{1:3}, at: __local_bh_disable_ip+0x3c/0x420 kernel/softirq.c:163 #7: ffff888068d4c3f0 (&cp->lock#2){+...}-{3:3}, at: spin_lock include/linux/spinlock_rt.h:45 [inline] #7: ffff888068d4c3f0 (&cp->lock#2){+...}-{3:3}, at: ip_vs_conn_unlink net/netfilter/ipvs/ip_vs_conn.c:324 [inline] #7: ffff888068d4c3f0 (&cp->lock#2){+...}-{3:3}, at: ip_vs_conn_expire+0xd4a/0x2390 net/netfilter/ipvs/ip_vs_conn.c:1260 Preemption disabled at: [] bit_spin_lock include/linux/bit_spinlock.h:38 [inline] [] hlist_bl_lock+0x18/0x110 include/linux/list_bl.h:149 CPU: 0 UID: 0 PID: 16 Comm: ktimers/0 Tainted: G W L syzkaller #0 PREEMPT_{RT,(full)} Tainted: [W]=WARN, [L]=SOFTLOCKUP Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/18/2026 Call Trace: dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120 __might_resched+0x329/0x480 kernel/sched/core.c:9162 __rt_spin_lock kernel/locking/spinlock_rt.c:48 [inline] rt_spin_lock+0xc2/0x400 kernel/locking/spinlock_rt.c:57 spin_lock include/linux/spinlock_rt.h:45 [inline] ip_vs_conn_unlink net/netfilter/ipvs/ip_vs_conn.c:324 [inline] ip_vs_conn_expire+0xd4a/0x2390 net/netfilter/ipvs/ip_vs_conn.c:1260 call_timer_fn+0x192/0x5e0 kernel/time/timer.c:1748 expire_timers kernel/time/timer.c:1799 [inline] __run_timers kernel/time/timer.c:2374 [inline] __run_timer_base+0x6a3/0x9f0 kernel/time/timer.c:2386 run_timer_base kernel/time/timer.c:2395 [inline] run_timer_softirq+0xb7/0x170 kernel/time/timer.c:2405 handle_softirqs+0x1de/0x6d0 kernel/softirq.c:622 __do_softirq kernel/softirq.c:656 [inline] run_ktimerd+0x69/0x100 kernel/softirq.c:1151 smpboot_thread_fn+0x541/0xa50 kernel/smpboot.c:160 kthread+0x388/0x470 kernel/kthread.c:436 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 Reported-by: syzbot+504e778ddaecd36fdd17@syzkaller.appspotmail.com Fixes: 2fa7cc9c7025 ("ipvs: switch to per-net connection table") Signed-off-by: Julian Anastasov --- net/netfilter/ipvs/ip_vs_conn.c | 49 ++++++++++++++------------------- 1 file changed, 21 insertions(+), 28 deletions(-) diff --git a/net/netfilter/ipvs/ip_vs_conn.c b/net/netfilter/ipvs/ip_vs_conn.c index 84a4921a7865..cf19dc06c65d 100644 --- a/net/netfilter/ipvs/ip_vs_conn.c +++ b/net/netfilter/ipvs/ip_vs_conn.c @@ -267,27 +267,20 @@ static inline int ip_vs_conn_hash(struct ip_vs_conn *cp) hash_key2 = hash_key; use2 = false; } + conn_tab_lock(t, cp, hash_key, hash_key2, use2, true /* new_hash */, &head, &head2); - spin_lock(&cp->lock); - - if (!(cp->flags & IP_VS_CONN_F_HASHED)) { - cp->flags |= IP_VS_CONN_F_HASHED; - WRITE_ONCE(cp->hn0.hash_key, hash_key); - WRITE_ONCE(cp->hn1.hash_key, hash_key2); - refcount_inc(&cp->refcnt); - hlist_bl_add_head_rcu(&cp->hn0.node, head); - if (use2) - hlist_bl_add_head_rcu(&cp->hn1.node, head2); - ret = 1; - } else { - pr_err("%s(): request for already hashed, called from %pS\n", - __func__, __builtin_return_address(0)); - ret = 0; - } - spin_unlock(&cp->lock); + cp->flags |= IP_VS_CONN_F_HASHED; + WRITE_ONCE(cp->hn0.hash_key, hash_key); + WRITE_ONCE(cp->hn1.hash_key, hash_key2); + refcount_inc(&cp->refcnt); + hlist_bl_add_head_rcu(&cp->hn0.node, head); + if (use2) + hlist_bl_add_head_rcu(&cp->hn1.node, head2); + conn_tab_unlock(head, head2); + ret = 1; /* Schedule resizing if load increases */ if (atomic_read(&ipvs->conn_count) > t->u_thresh && @@ -321,7 +314,6 @@ static inline bool ip_vs_conn_unlink(struct ip_vs_conn *cp) conn_tab_lock(t, cp, hash_key, hash_key2, use2, false /* new_hash */, &head, &head2); - spin_lock(&cp->lock); if (cp->flags & IP_VS_CONN_F_HASHED) { /* Decrease refcnt and unlink conn only if we are last user */ @@ -334,7 +326,6 @@ static inline bool ip_vs_conn_unlink(struct ip_vs_conn *cp) } } - spin_unlock(&cp->lock); conn_tab_unlock(head, head2); rcu_read_unlock(); @@ -637,6 +628,7 @@ void ip_vs_conn_fill_cport(struct ip_vs_conn *cp, __be16 cport) struct ip_vs_conn_hnode *hn; u32 hash_key, hash_key_new; struct ip_vs_conn_param p; + bool changed = false; int ntbl; int dir; @@ -709,9 +701,7 @@ void ip_vs_conn_fill_cport(struct ip_vs_conn *cp, __be16 cport) goto retry; } - spin_lock(&cp->lock); - if ((cp->flags & IP_VS_CONN_F_NO_CPORT) && - (cp->flags & IP_VS_CONN_F_HASHED)) { + if (cp->flags & IP_VS_CONN_F_NO_CPORT) { /* We do not recalc hash_key_r under lock, we assume the * parameters in cp do not change, i.e. cport is * the only possible change. @@ -726,19 +716,22 @@ void ip_vs_conn_fill_cport(struct ip_vs_conn *cp, __be16 cport) hlist_bl_del_rcu(&hn->node); hlist_bl_add_head_rcu(&hn->node, head_new); } - if (!dir) { - atomic_dec(&ipvs->no_cport_conns[af_id]); - cp->flags &= ~IP_VS_CONN_F_NO_CPORT; - cp->cport = cport; - } + if (!dir) + changed = true; } - spin_unlock(&cp->lock); if (head != head2) hlist_bl_unlock(head2); hlist_bl_unlock(head); write_seqcount_end(&t->seqc[hash_key & t->seqc_mask]); preempt_enable_nested(); + if (changed) { + atomic_dec(&ipvs->no_cport_conns[af_id]); + spin_lock(&cp->lock); + cp->flags &= ~IP_VS_CONN_F_NO_CPORT; + cp->cport = cport; + spin_unlock(&cp->lock); + } spin_unlock_bh(&t->lock[hash_key & t->lock_mask].l); if (dir--) goto next_dir; -- 2.53.0