* [PATCH net] net/sched: fix lockdep splat in qdisc_tree_reduce_backlog()
@ 2024-04-02 13:41 Eric Dumazet
2024-04-02 14:39 ` Jiri Pirko
` (2 more replies)
0 siblings, 3 replies; 4+ messages in thread
From: Eric Dumazet @ 2024-04-02 13:41 UTC (permalink / raw)
To: David S . Miller, Jakub Kicinski, Paolo Abeni
Cc: Jamal Hadi Salim, Cong Wang, Jiri Pirko, netdev, eric.dumazet,
Eric Dumazet, syzbot
qdisc_tree_reduce_backlog() is called with the qdisc lock held,
not RTNL.
We must use qdisc_lookup_rcu() instead of qdisc_lookup()
syzbot reported:
WARNING: suspicious RCU usage
6.1.74-syzkaller #0 Not tainted
-----------------------------
net/sched/sch_api.c:305 suspicious rcu_dereference_protected() usage!
other info that might help us debug this:
rcu_scheduler_active = 2, debug_locks = 1
3 locks held by udevd/1142:
#0: ffffffff87c729a0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:306 [inline]
#0: ffffffff87c729a0 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:747 [inline]
#0: ffffffff87c729a0 (rcu_read_lock){....}-{1:2}, at: net_tx_action+0x64a/0x970 net/core/dev.c:5282
#1: ffff888171861108 (&sch->q.lock){+.-.}-{2:2}, at: spin_lock include/linux/spinlock.h:350 [inline]
#1: ffff888171861108 (&sch->q.lock){+.-.}-{2:2}, at: net_tx_action+0x754/0x970 net/core/dev.c:5297
#2: ffffffff87c729a0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:306 [inline]
#2: ffffffff87c729a0 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:747 [inline]
#2: ffffffff87c729a0 (rcu_read_lock){....}-{1:2}, at: qdisc_tree_reduce_backlog+0x84/0x580 net/sched/sch_api.c:792
stack backtrace:
CPU: 1 PID: 1142 Comm: udevd Not tainted 6.1.74-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/25/2024
Call Trace:
<TASK>
[<ffffffff85b85f14>] __dump_stack lib/dump_stack.c:88 [inline]
[<ffffffff85b85f14>] dump_stack_lvl+0x1b1/0x28f lib/dump_stack.c:106
[<ffffffff85b86007>] dump_stack+0x15/0x1e lib/dump_stack.c:113
[<ffffffff81802299>] lockdep_rcu_suspicious+0x1b9/0x260 kernel/locking/lockdep.c:6592
[<ffffffff84f0054c>] qdisc_lookup+0xac/0x6f0 net/sched/sch_api.c:305
[<ffffffff84f037c3>] qdisc_tree_reduce_backlog+0x243/0x580 net/sched/sch_api.c:811
[<ffffffff84f5b78c>] pfifo_tail_enqueue+0x32c/0x4b0 net/sched/sch_fifo.c:51
[<ffffffff84fbcf63>] qdisc_enqueue include/net/sch_generic.h:833 [inline]
[<ffffffff84fbcf63>] netem_dequeue+0xeb3/0x15d0 net/sched/sch_netem.c:723
[<ffffffff84eecab9>] dequeue_skb net/sched/sch_generic.c:292 [inline]
[<ffffffff84eecab9>] qdisc_restart net/sched/sch_generic.c:397 [inline]
[<ffffffff84eecab9>] __qdisc_run+0x249/0x1e60 net/sched/sch_generic.c:415
[<ffffffff84d7aa96>] qdisc_run+0xd6/0x260 include/net/pkt_sched.h:125
[<ffffffff84d85d29>] net_tx_action+0x7c9/0x970 net/core/dev.c:5313
[<ffffffff85e002bd>] __do_softirq+0x2bd/0x9bd kernel/softirq.c:616
[<ffffffff81568bca>] invoke_softirq kernel/softirq.c:447 [inline]
[<ffffffff81568bca>] __irq_exit_rcu+0xca/0x230 kernel/softirq.c:700
[<ffffffff81568ae9>] irq_exit_rcu+0x9/0x20 kernel/softirq.c:712
[<ffffffff85b89f52>] sysvec_apic_timer_interrupt+0x42/0x90 arch/x86/kernel/apic/apic.c:1107
[<ffffffff85c00ccb>] asm_sysvec_apic_timer_interrupt+0x1b/0x20 arch/x86/include/asm/idtentry.h:656
Fixes: d636fc5dd692 ("net: sched: add rcu annotations around qdisc->qdisc_sleeping")
Reported-by: syzbot <syzkaller@googlegroups.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
---
net/sched/sch_api.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/net/sched/sch_api.c b/net/sched/sch_api.c
index 65e05b0c98e461953aa8d98020142f0abe3ad8a7..60239378d43fb7adfe3926f927f3883f09673c16 100644
--- a/net/sched/sch_api.c
+++ b/net/sched/sch_api.c
@@ -809,7 +809,7 @@ void qdisc_tree_reduce_backlog(struct Qdisc *sch, int n, int len)
notify = !sch->q.qlen && !WARN_ON_ONCE(!n &&
!qdisc_is_offloaded);
/* TODO: perform the search on a per txq basis */
- sch = qdisc_lookup(qdisc_dev(sch), TC_H_MAJ(parentid));
+ sch = qdisc_lookup_rcu(qdisc_dev(sch), TC_H_MAJ(parentid));
if (sch == NULL) {
WARN_ON_ONCE(parentid != TC_H_ROOT);
break;
--
2.44.0.478.gd926399ef9-goog
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH net] net/sched: fix lockdep splat in qdisc_tree_reduce_backlog()
2024-04-02 13:41 [PATCH net] net/sched: fix lockdep splat in qdisc_tree_reduce_backlog() Eric Dumazet
@ 2024-04-02 14:39 ` Jiri Pirko
2024-04-02 16:37 ` Jamal Hadi Salim
2024-04-04 2:40 ` patchwork-bot+netdevbpf
2 siblings, 0 replies; 4+ messages in thread
From: Jiri Pirko @ 2024-04-02 14:39 UTC (permalink / raw)
To: Eric Dumazet
Cc: David S . Miller, Jakub Kicinski, Paolo Abeni, Jamal Hadi Salim,
Cong Wang, netdev, eric.dumazet, syzbot
Tue, Apr 02, 2024 at 03:41:33PM CEST, edumazet@google.com wrote:
>qdisc_tree_reduce_backlog() is called with the qdisc lock held,
>not RTNL.
>
>We must use qdisc_lookup_rcu() instead of qdisc_lookup()
>
>syzbot reported:
>
>WARNING: suspicious RCU usage
>6.1.74-syzkaller #0 Not tainted
>-----------------------------
>net/sched/sch_api.c:305 suspicious rcu_dereference_protected() usage!
>
>other info that might help us debug this:
>
>rcu_scheduler_active = 2, debug_locks = 1
>3 locks held by udevd/1142:
> #0: ffffffff87c729a0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:306 [inline]
> #0: ffffffff87c729a0 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:747 [inline]
> #0: ffffffff87c729a0 (rcu_read_lock){....}-{1:2}, at: net_tx_action+0x64a/0x970 net/core/dev.c:5282
> #1: ffff888171861108 (&sch->q.lock){+.-.}-{2:2}, at: spin_lock include/linux/spinlock.h:350 [inline]
> #1: ffff888171861108 (&sch->q.lock){+.-.}-{2:2}, at: net_tx_action+0x754/0x970 net/core/dev.c:5297
> #2: ffffffff87c729a0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:306 [inline]
> #2: ffffffff87c729a0 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:747 [inline]
> #2: ffffffff87c729a0 (rcu_read_lock){....}-{1:2}, at: qdisc_tree_reduce_backlog+0x84/0x580 net/sched/sch_api.c:792
>
>stack backtrace:
>CPU: 1 PID: 1142 Comm: udevd Not tainted 6.1.74-syzkaller #0
>Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/25/2024
>Call Trace:
> <TASK>
> [<ffffffff85b85f14>] __dump_stack lib/dump_stack.c:88 [inline]
> [<ffffffff85b85f14>] dump_stack_lvl+0x1b1/0x28f lib/dump_stack.c:106
> [<ffffffff85b86007>] dump_stack+0x15/0x1e lib/dump_stack.c:113
> [<ffffffff81802299>] lockdep_rcu_suspicious+0x1b9/0x260 kernel/locking/lockdep.c:6592
> [<ffffffff84f0054c>] qdisc_lookup+0xac/0x6f0 net/sched/sch_api.c:305
> [<ffffffff84f037c3>] qdisc_tree_reduce_backlog+0x243/0x580 net/sched/sch_api.c:811
> [<ffffffff84f5b78c>] pfifo_tail_enqueue+0x32c/0x4b0 net/sched/sch_fifo.c:51
> [<ffffffff84fbcf63>] qdisc_enqueue include/net/sch_generic.h:833 [inline]
> [<ffffffff84fbcf63>] netem_dequeue+0xeb3/0x15d0 net/sched/sch_netem.c:723
> [<ffffffff84eecab9>] dequeue_skb net/sched/sch_generic.c:292 [inline]
> [<ffffffff84eecab9>] qdisc_restart net/sched/sch_generic.c:397 [inline]
> [<ffffffff84eecab9>] __qdisc_run+0x249/0x1e60 net/sched/sch_generic.c:415
> [<ffffffff84d7aa96>] qdisc_run+0xd6/0x260 include/net/pkt_sched.h:125
> [<ffffffff84d85d29>] net_tx_action+0x7c9/0x970 net/core/dev.c:5313
> [<ffffffff85e002bd>] __do_softirq+0x2bd/0x9bd kernel/softirq.c:616
> [<ffffffff81568bca>] invoke_softirq kernel/softirq.c:447 [inline]
> [<ffffffff81568bca>] __irq_exit_rcu+0xca/0x230 kernel/softirq.c:700
> [<ffffffff81568ae9>] irq_exit_rcu+0x9/0x20 kernel/softirq.c:712
> [<ffffffff85b89f52>] sysvec_apic_timer_interrupt+0x42/0x90 arch/x86/kernel/apic/apic.c:1107
> [<ffffffff85c00ccb>] asm_sysvec_apic_timer_interrupt+0x1b/0x20 arch/x86/include/asm/idtentry.h:656
>
>Fixes: d636fc5dd692 ("net: sched: add rcu annotations around qdisc->qdisc_sleeping")
>Reported-by: syzbot <syzkaller@googlegroups.com>
>Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Jiri Pirko <jiri@nvidia.com>
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH net] net/sched: fix lockdep splat in qdisc_tree_reduce_backlog()
2024-04-02 13:41 [PATCH net] net/sched: fix lockdep splat in qdisc_tree_reduce_backlog() Eric Dumazet
2024-04-02 14:39 ` Jiri Pirko
@ 2024-04-02 16:37 ` Jamal Hadi Salim
2024-04-04 2:40 ` patchwork-bot+netdevbpf
2 siblings, 0 replies; 4+ messages in thread
From: Jamal Hadi Salim @ 2024-04-02 16:37 UTC (permalink / raw)
To: Eric Dumazet
Cc: David S . Miller, Jakub Kicinski, Paolo Abeni, Cong Wang,
Jiri Pirko, netdev, eric.dumazet, syzbot
On Tue, Apr 2, 2024 at 9:41 AM Eric Dumazet <edumazet@google.com> wrote:
>
> qdisc_tree_reduce_backlog() is called with the qdisc lock held,
> not RTNL.
>
> We must use qdisc_lookup_rcu() instead of qdisc_lookup()
>
> syzbot reported:
>
> WARNING: suspicious RCU usage
> 6.1.74-syzkaller #0 Not tainted
> -----------------------------
> net/sched/sch_api.c:305 suspicious rcu_dereference_protected() usage!
>
> other info that might help us debug this:
>
> rcu_scheduler_active = 2, debug_locks = 1
> 3 locks held by udevd/1142:
> #0: ffffffff87c729a0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:306 [inline]
> #0: ffffffff87c729a0 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:747 [inline]
> #0: ffffffff87c729a0 (rcu_read_lock){....}-{1:2}, at: net_tx_action+0x64a/0x970 net/core/dev.c:5282
> #1: ffff888171861108 (&sch->q.lock){+.-.}-{2:2}, at: spin_lock include/linux/spinlock.h:350 [inline]
> #1: ffff888171861108 (&sch->q.lock){+.-.}-{2:2}, at: net_tx_action+0x754/0x970 net/core/dev.c:5297
> #2: ffffffff87c729a0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:306 [inline]
> #2: ffffffff87c729a0 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:747 [inline]
> #2: ffffffff87c729a0 (rcu_read_lock){....}-{1:2}, at: qdisc_tree_reduce_backlog+0x84/0x580 net/sched/sch_api.c:792
>
> stack backtrace:
> CPU: 1 PID: 1142 Comm: udevd Not tainted 6.1.74-syzkaller #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/25/2024
> Call Trace:
> <TASK>
> [<ffffffff85b85f14>] __dump_stack lib/dump_stack.c:88 [inline]
> [<ffffffff85b85f14>] dump_stack_lvl+0x1b1/0x28f lib/dump_stack.c:106
> [<ffffffff85b86007>] dump_stack+0x15/0x1e lib/dump_stack.c:113
> [<ffffffff81802299>] lockdep_rcu_suspicious+0x1b9/0x260 kernel/locking/lockdep.c:6592
> [<ffffffff84f0054c>] qdisc_lookup+0xac/0x6f0 net/sched/sch_api.c:305
> [<ffffffff84f037c3>] qdisc_tree_reduce_backlog+0x243/0x580 net/sched/sch_api.c:811
> [<ffffffff84f5b78c>] pfifo_tail_enqueue+0x32c/0x4b0 net/sched/sch_fifo.c:51
> [<ffffffff84fbcf63>] qdisc_enqueue include/net/sch_generic.h:833 [inline]
> [<ffffffff84fbcf63>] netem_dequeue+0xeb3/0x15d0 net/sched/sch_netem.c:723
> [<ffffffff84eecab9>] dequeue_skb net/sched/sch_generic.c:292 [inline]
> [<ffffffff84eecab9>] qdisc_restart net/sched/sch_generic.c:397 [inline]
> [<ffffffff84eecab9>] __qdisc_run+0x249/0x1e60 net/sched/sch_generic.c:415
> [<ffffffff84d7aa96>] qdisc_run+0xd6/0x260 include/net/pkt_sched.h:125
> [<ffffffff84d85d29>] net_tx_action+0x7c9/0x970 net/core/dev.c:5313
> [<ffffffff85e002bd>] __do_softirq+0x2bd/0x9bd kernel/softirq.c:616
> [<ffffffff81568bca>] invoke_softirq kernel/softirq.c:447 [inline]
> [<ffffffff81568bca>] __irq_exit_rcu+0xca/0x230 kernel/softirq.c:700
> [<ffffffff81568ae9>] irq_exit_rcu+0x9/0x20 kernel/softirq.c:712
> [<ffffffff85b89f52>] sysvec_apic_timer_interrupt+0x42/0x90 arch/x86/kernel/apic/apic.c:1107
> [<ffffffff85c00ccb>] asm_sysvec_apic_timer_interrupt+0x1b/0x20 arch/x86/include/asm/idtentry.h:656
>
> Fixes: d636fc5dd692 ("net: sched: add rcu annotations around qdisc->qdisc_sleeping")
> Reported-by: syzbot <syzkaller@googlegroups.com>
> Signed-off-by: Eric Dumazet <edumazet@google.com>
LGTM.
Acked-by: Jamal Hadi Salim <jhs@mojatatu.com>
cheers,
jamal
> ---
> net/sched/sch_api.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/net/sched/sch_api.c b/net/sched/sch_api.c
> index 65e05b0c98e461953aa8d98020142f0abe3ad8a7..60239378d43fb7adfe3926f927f3883f09673c16 100644
> --- a/net/sched/sch_api.c
> +++ b/net/sched/sch_api.c
> @@ -809,7 +809,7 @@ void qdisc_tree_reduce_backlog(struct Qdisc *sch, int n, int len)
> notify = !sch->q.qlen && !WARN_ON_ONCE(!n &&
> !qdisc_is_offloaded);
> /* TODO: perform the search on a per txq basis */
> - sch = qdisc_lookup(qdisc_dev(sch), TC_H_MAJ(parentid));
> + sch = qdisc_lookup_rcu(qdisc_dev(sch), TC_H_MAJ(parentid));
> if (sch == NULL) {
> WARN_ON_ONCE(parentid != TC_H_ROOT);
> break;
> --
> 2.44.0.478.gd926399ef9-goog
>
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH net] net/sched: fix lockdep splat in qdisc_tree_reduce_backlog()
2024-04-02 13:41 [PATCH net] net/sched: fix lockdep splat in qdisc_tree_reduce_backlog() Eric Dumazet
2024-04-02 14:39 ` Jiri Pirko
2024-04-02 16:37 ` Jamal Hadi Salim
@ 2024-04-04 2:40 ` patchwork-bot+netdevbpf
2 siblings, 0 replies; 4+ messages in thread
From: patchwork-bot+netdevbpf @ 2024-04-04 2:40 UTC (permalink / raw)
To: Eric Dumazet
Cc: davem, kuba, pabeni, jhs, xiyou.wangcong, jiri, netdev,
eric.dumazet, syzkaller
Hello:
This patch was applied to netdev/net.git (main)
by Jakub Kicinski <kuba@kernel.org>:
On Tue, 2 Apr 2024 13:41:33 +0000 you wrote:
> qdisc_tree_reduce_backlog() is called with the qdisc lock held,
> not RTNL.
>
> We must use qdisc_lookup_rcu() instead of qdisc_lookup()
>
> syzbot reported:
>
> [...]
Here is the summary with links:
- [net] net/sched: fix lockdep splat in qdisc_tree_reduce_backlog()
https://git.kernel.org/netdev/net/c/7eb322360b02
You are awesome, thank you!
--
Deet-doot-dot, I am a bot.
https://korg.docs.kernel.org/patchwork/pwbot.html
^ permalink raw reply [flat|nested] 4+ messages in thread
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2024-04-02 13:41 [PATCH net] net/sched: fix lockdep splat in qdisc_tree_reduce_backlog() Eric Dumazet
2024-04-02 14:39 ` Jiri Pirko
2024-04-02 16:37 ` Jamal Hadi Salim
2024-04-04 2:40 ` patchwork-bot+netdevbpf
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