3.16.72-rc1 review patch. If anyone has any objections, please let me know.
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From: Eric Dumazet edumazet@google.com
commit 0453c682459583910d611a96de928f4442205493 upstream.
This patch adds a limit on the number of skbs that fuzzers can queue into loopback_queue. 1000 packets for rose loopback seems more than enough.
Then, since we now have multiple cpus in most linux hosts, we also need to limit the number of skbs rose_loopback_timer() can dequeue at each round.
rose_loopback_queue() can be drop-monitor friendly, calling consume_skb() or kfree_skb() appropriately.
Finally, use mod_timer() instead of del_timer() + add_timer()
syzbot report was :
rcu: INFO: rcu_preempt self-detected stall on CPU rcu: 0-...!: (10499 ticks this GP) idle=536/1/0x4000000000000002 softirq=103291/103291 fqs=34 rcu: (t=10500 jiffies g=140321 q=323) rcu: rcu_preempt kthread starved for 10426 jiffies! g140321 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x402 ->cpu=1 rcu: RCU grace-period kthread stack dump: rcu_preempt I29168 10 2 0x80000000 Call Trace: context_switch kernel/sched/core.c:2877 [inline] __schedule+0x813/0x1cc0 kernel/sched/core.c:3518 schedule+0x92/0x180 kernel/sched/core.c:3562 schedule_timeout+0x4db/0xfd0 kernel/time/timer.c:1803 rcu_gp_fqs_loop kernel/rcu/tree.c:1971 [inline] rcu_gp_kthread+0x962/0x17b0 kernel/rcu/tree.c:2128 kthread+0x357/0x430 kernel/kthread.c:253 ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:352 NMI backtrace for cpu 0 CPU: 0 PID: 7632 Comm: kworker/0:4 Not tainted 5.1.0-rc5+ #172 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Workqueue: events iterate_cleanup_work Call Trace: <IRQ> __dump_stack lib/dump_stack.c:77 [inline] dump_stack+0x172/0x1f0 lib/dump_stack.c:113 nmi_cpu_backtrace.cold+0x63/0xa4 lib/nmi_backtrace.c:101 nmi_trigger_cpumask_backtrace+0x1be/0x236 lib/nmi_backtrace.c:62 arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:38 trigger_single_cpu_backtrace include/linux/nmi.h:164 [inline] rcu_dump_cpu_stacks+0x183/0x1cf kernel/rcu/tree.c:1223 print_cpu_stall kernel/rcu/tree.c:1360 [inline] check_cpu_stall kernel/rcu/tree.c:1434 [inline] rcu_pending kernel/rcu/tree.c:3103 [inline] rcu_sched_clock_irq.cold+0x500/0xa4a kernel/rcu/tree.c:2544 update_process_times+0x32/0x80 kernel/time/timer.c:1635 tick_sched_handle+0xa2/0x190 kernel/time/tick-sched.c:161 tick_sched_timer+0x47/0x130 kernel/time/tick-sched.c:1271 __run_hrtimer kernel/time/hrtimer.c:1389 [inline] __hrtimer_run_queues+0x33e/0xde0 kernel/time/hrtimer.c:1451 hrtimer_interrupt+0x314/0x770 kernel/time/hrtimer.c:1509 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1035 [inline] smp_apic_timer_interrupt+0x120/0x570 arch/x86/kernel/apic/apic.c:1060 apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:807 RIP: 0010:__sanitizer_cov_trace_pc+0x0/0x50 kernel/kcov.c:95 Code: 89 25 b4 6e ec 08 41 bc f4 ff ff ff e8 cd 5d ea ff 48 c7 05 9e 6e ec 08 00 00 00 00 e9 a4 e9 ff ff 90 90 90 90 90 90 90 90 90 <55> 48 89 e5 48 8b 75 08 65 48 8b 04 25 00 ee 01 00 65 8b 15 c8 60 RSP: 0018:ffff8880ae807ce0 EFLAGS: 00000286 ORIG_RAX: ffffffffffffff13 RAX: ffff88806fd40640 RBX: dffffc0000000000 RCX: ffffffff863fbc56 RDX: 0000000000000100 RSI: ffffffff863fbc1d RDI: ffff88808cf94228 RBP: ffff8880ae807d10 R08: ffff88806fd40640 R09: ffffed1015d00f8b R10: ffffed1015d00f8a R11: 0000000000000003 R12: ffff88808cf941c0 R13: 00000000fffff034 R14: ffff8882166cd840 R15: 0000000000000000 rose_loopback_timer+0x30d/0x3f0 net/rose/rose_loopback.c:91 call_timer_fn+0x190/0x720 kernel/time/timer.c:1325 expire_timers kernel/time/timer.c:1362 [inline] __run_timers kernel/time/timer.c:1681 [inline] __run_timers kernel/time/timer.c:1649 [inline] run_timer_softirq+0x652/0x1700 kernel/time/timer.c:1694 __do_softirq+0x266/0x95a kernel/softirq.c:293 do_softirq_own_stack+0x2a/0x40 arch/x86/entry/entry_64.S:1027
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Signed-off-by: Eric Dumazet edumazet@google.com Reported-by: syzbot syzkaller@googlegroups.com Signed-off-by: David S. Miller davem@davemloft.net [bwh: Backported to 3.16: Also move assignments to loopback_timer.{data,function} into rose_loopback_init(), done upstream in commit 4966babd904d "net/rose: Convert timers to use timer_setup()".] Signed-off-by: Ben Hutchings ben@decadent.org.uk --- net/rose/rose_loopback.c | 27 ++++++++++++++++----------- 1 file changed, 16 insertions(+), 11 deletions(-)
--- a/net/rose/rose_loopback.c +++ b/net/rose/rose_loopback.c @@ -16,15 +16,19 @@ #include <linux/init.h>
static struct sk_buff_head loopback_queue; +#define ROSE_LOOPBACK_LIMIT 1000 static struct timer_list loopback_timer;
static void rose_set_loopback_timer(void); +static void rose_loopback_timer(unsigned long);
void rose_loopback_init(void) { skb_queue_head_init(&loopback_queue);
init_timer(&loopback_timer); + loopback_timer.data = 0; + loopback_timer.function = &rose_loopback_timer; }
static int rose_loopback_running(void) @@ -34,33 +38,27 @@ static int rose_loopback_running(void)
int rose_loopback_queue(struct sk_buff *skb, struct rose_neigh *neigh) { - struct sk_buff *skbn; + struct sk_buff *skbn = NULL;
- skbn = skb_clone(skb, GFP_ATOMIC); + if (skb_queue_len(&loopback_queue) < ROSE_LOOPBACK_LIMIT) + skbn = skb_clone(skb, GFP_ATOMIC);
- kfree_skb(skb); - - if (skbn != NULL) { + if (skbn) { + consume_skb(skb); skb_queue_tail(&loopback_queue, skbn);
if (!rose_loopback_running()) rose_set_loopback_timer(); + } else { + kfree_skb(skb); }
return 1; }
-static void rose_loopback_timer(unsigned long); - static void rose_set_loopback_timer(void) { - del_timer(&loopback_timer); - - loopback_timer.data = 0; - loopback_timer.function = &rose_loopback_timer; - loopback_timer.expires = jiffies + 10; - - add_timer(&loopback_timer); + mod_timer(&loopback_timer, jiffies + 10); }
static void rose_loopback_timer(unsigned long param) @@ -71,8 +69,12 @@ static void rose_loopback_timer(unsigned struct sock *sk; unsigned short frametype; unsigned int lci_i, lci_o; + int count;
- while ((skb = skb_dequeue(&loopback_queue)) != NULL) { + for (count = 0; count < ROSE_LOOPBACK_LIMIT; count++) { + skb = skb_dequeue(&loopback_queue); + if (!skb) + return; if (skb->len < ROSE_MIN_LEN) { kfree_skb(skb); continue; @@ -109,6 +111,8 @@ static void rose_loopback_timer(unsigned kfree_skb(skb); } } + if (!skb_queue_empty(&loopback_queue)) + mod_timer(&loopback_timer, jiffies + 1); }
void __exit rose_loopback_clear(void)