On Thu, Jan 4, 2018 at 1:57 PM, Takashi Iwai tiwai@suse.de wrote:
On Thu, 04 Jan 2018 13:08:45 +0100, Dmitry Vyukov wrote:
On Thu, Jan 4, 2018 at 1:03 PM, syzbot syzbot+387f48da65cb522abfe8@syzkaller.appspotmail.com wrote:
Hello,
syzkaller hit the following crash on 30a7acd573899fd8b8ac39236eff6468b195ac7d git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/master compiler: gcc (GCC) 7.1.1 20170620 .config is attached Raw console output is attached. Unfortunately, I don't have any reproducer for this bug yet.
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This looks ALSA-related. +ALSA maintainers.
Not sure exactly what triggers it. It's the simple memcpy(), and I don't know where RCU is involved in that code path.
BTW, other two suspicious RCU usage reports are actually stopped at the second WARN_ON() after the RCU message, and the second WARN_ON() is independent from RCU; it's the known spurious WARN_ON() and was already removed in the sound git tree.
Hi Takashi,
Another similar one just popped up:
https://groups.google.com/forum/#!topic/syzkaller-bugs/X3d6-PIrJM0
This looks like mulaw_decode enters an infinite loop, or at least doing very large amount of computations without a resched, e.g. (uint64_t)-1 number of iterations of something along these lines.
INFO: rcu_sched detected stalls on CPUs/tasks: (detected by 0, t=125002 jiffies, g=15654, c=15653, q=133) All QSes seen, last rcu_sched kthread activity 125002 (4294863411-4294738409), jiffies_till_next_fqs=3, root ->qsmask 0x0 syz-executor1 R running task 24936 11943 3739 0x0000000c Call Trace:
<IRQ> sched_show_task+0x4a3/0x5e0 kernel/sched/core.c:5198 print_other_cpu_stall+0x996/0x1090 kernel/rcu/tree.c:1564 check_cpu_stall.isra.61+0x6e6/0x15b0 kernel/rcu/tree.c:1682 __rcu_pending kernel/rcu/tree.c:3440 [inline] rcu_pending kernel/rcu/tree.c:3502 [inline] rcu_check_callbacks+0x256/0xd00 kernel/rcu/tree.c:2842 update_process_times+0x30/0x60 kernel/time/timer.c:1628 tick_sched_handle+0x85/0x160 kernel/time/tick-sched.c:162 tick_sched_timer+0x42/0x120 kernel/time/tick-sched.c:1194 __run_hrtimer kernel/time/hrtimer.c:1211 [inline] __hrtimer_run_queues+0x358/0xe20 kernel/time/hrtimer.c:1275 hrtimer_interrupt+0x1c2/0x5e0 kernel/time/hrtimer.c:1309 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1025 [inline] smp_apic_timer_interrupt+0x14a/0x700 arch/x86/kernel/apic/apic.c:1050 apic_timer_interrupt+0xa9/0xb0 arch/x86/entry/entry_64.S:920 </IRQ> RIP: 0010:kasan_mem_to_shadow include/linux/kasan.h:30 [inline] RIP: 0010:memory_is_poisoned_n mm/kasan/kasan.c:210 [inline] RIP: 0010:memory_is_poisoned mm/kasan/kasan.c:241 [inline] RIP: 0010:check_memory_region_inline mm/kasan/kasan.c:257 [inline] RIP: 0010:check_memory_region+0x38/0x190 mm/kasan/kasan.c:267 RSP: 0000:ffff8801bd2ff868 EFLAGS: 00000212 ORIG_RAX: ffffffffffffff11 RAX: ffff7fffffffffff RBX: ffffc9000160020b RCX: ffffffff841fceaf RDX: 0000000000000001 RSI: 0000000000000002 RDI: ffffc9000160020a RBP: ffff8801bd2ff878 R08: ffffc9000160020a R09: dffffc0000000000 R10: 0000000000000001 R11: ffffed0037a5ff2e R12: ffffc9000160020a R13: ffff8801bd2ff970 R14: dffffc0000000000 R15: ffffc9000160020a memcpy+0x37/0x50 mm/kasan/kasan.c:303 memcpy include/linux/string.h:344 [inline] cvt_s16_to_native sound/core/oss/mulaw.c:164 [inline] mulaw_decode+0x52f/0x770 sound/core/oss/mulaw.c:195 mulaw_transfer+0x222/0x270 sound/core/oss/mulaw.c:273 snd_pcm_plug_write_transfer+0x22d/0x420 sound/core/oss/pcm_plugin.c:611 snd_pcm_oss_write2+0x260/0x420 sound/core/oss/pcm_oss.c:1311 snd_pcm_oss_write1 sound/core/oss/pcm_oss.c:1372 [inline] snd_pcm_oss_write+0x5fe/0x830 sound/core/oss/pcm_oss.c:2646 __vfs_write+0xef/0x970 fs/read_write.c:480 vfs_write+0x189/0x510 fs/read_write.c:544 SYSC_write fs/read_write.c:589 [inline] SyS_write+0xef/0x220 fs/read_write.c:581 entry_SYSCALL_64_fastpath+0x23/0x9a RIP: 0033:0x452ac9 RSP: 002b:00007fa354a13c58 EFLAGS: 00000212 ORIG_RAX: 0000000000000001 RAX: ffffffffffffffda RBX: cccccccccccccccd RCX: 0000000000452ac9 RDX: 00000000fffffeb2 RSI: 0000000020083fc6 RDI: 0000000000000014 RBP: 00000000000005b5 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000212 R12: 00000000006f6998 R13: 00000000ffffffff R14: 00007fa354a146d4 R15: 0000000000000000 rcu_sched kthread starved for 125002 jiffies! g15654 c15653 f0x2 RCU_GP_WAIT_FQS(3) ->state=0x0 ->cpu=0 rcu_sched R running task 23456 8 2 0x80000000 Call Trace: context_switch kernel/sched/core.c:2799 [inline] __schedule+0x8eb/0x2060 kernel/sched/core.c:3375 schedule+0xf5/0x430 kernel/sched/core.c:3434 schedule_timeout+0x118/0x230 kernel/time/timer.c:1793 rcu_gp_kthread+0x9e5/0x1930 kernel/rcu/tree.c:2314 kthread+0x33c/0x400 kernel/kthread.c:238 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:524
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