> > From: Thomas Gleixner <t...@linutronix.de> > To: Dave Jones <da...@codemonkey.org.uk> > Cc: Linux Kernel <linux-kernel@vger.kernel.org>, Steven Rostedt > <rost...@goodmis.org>, Ursula Braun <ubr...@linux.vnet.ibm.com>, > net...@vger.kernel.org > Date: 21.03.2017 22:46 > Subject: Re: run_timer_softirq gpf. [smc] > Sent by: netdev-ow...@vger.kernel.org > > > > On Tue, 21 Mar 2017, Dave Jones wrote: >> On Tue, Mar 21, 2017 at 08:25:39PM +0100, Thomas Gleixner wrote: >> >> > > I just hit this while fuzzing.. >> > > >> > > general protection fault: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC >> > > CPU: 2 PID: 0 Comm: swapper/2 Not tainted 4.11.0-rc2-think+ #1 >> > > task: ffff88017f0ed440 task.stack: ffffc90000094000 >> > > RIP: 0010:run_timer_softirq+0x15f/0x700 >> > > RSP: 0018:ffff880507c03ec8 EFLAGS: 00010086 >> > > RAX: dead000000000200 RBX: ffff880507dd0d00 RCX: 0000000000000002 >> > > RDX: ffff880507c03ed0 RSI: 00000000ffffffff RDI: ffffffff8204b3a0 >> > > RBP: ffff880507c03f48 R08: ffff880507dd12d0 R09: ffff880507c03ed8 >> > > R10: ffff880507dd0db0 R11: 0000000000000000 R12: ffffffff8215cc38 >> > > R13: ffff880507c03ed0 R14: ffffffff82005188 R15: ffff8804b55491a8 >> > > FS: 0000000000000000(0000) GS:ffff880507c00000(0000) > knlGS:0000000000000000 >> > > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 >> > > CR2: 0000000000000004 CR3: 0000000005011000 CR4: 00000000001406e0 >> > > Call Trace: >> > > <IRQ> >> > > ? clockevents_program_event+0x47/0x120 >> > > __do_softirq+0xbf/0x5b1 >> > > irq_exit+0xb5/0xc0 >> > > smp_apic_timer_interrupt+0x3d/0x50 >> > > apic_timer_interrupt+0x97/0xa0 >> > > RIP: 0010:cpuidle_enter_state+0x12e/0x400 >> > > RSP: 0018:ffffc90000097e40 EFLAGS: 00000202 >> > > [CONT START] ORIG_RAX: ffffffffffffff10 >> > > RAX: ffff88017f0ed440 RBX: ffffe8ffffa03cc8 RCX: 0000000000000001 >> > > RDX: 20c49ba5e353f7cf RSI: 0000000000000001 RDI: ffff88017f0ed440 >> > > RBP: ffffc90000097e80 R08: 00000000ffffffff R09: 0000000000000008 >> > > R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000005 >> > > R13: ffffffff820b9338 R14: 0000000000000005 R15: ffffffff820b9320 >> > > </IRQ> >> > > cpuidle_enter+0x17/0x20 >> > > call_cpuidle+0x23/0x40 >> > > do_idle+0xfb/0x200 >> > > cpu_startup_entry+0x71/0x80 >> > > start_secondary+0x16a/0x210 >> > > start_cpu+0x14/0x14 >> > > Code: 8b 05 ce 1b ef 7e 83 f8 03 0f 87 4e 01 00 00 89 c0 49 0f a3 > 04 24 0f 82 0a 01 00 00 49 8b 07 49 8b 57 08 48 85 c0 48 89 02 74 04 <48> > 89 50 08 41 f6 47 2a 20 49 c7 47 08 00 00 00 00 48 89 df 48 >> > >> > The timer which expires has timer->entry.next == POISON2 ! >> > >> > it's a classic list corruption. The >> > bad news is that there is no trace of the culprit because that > happens when >> > some other timer expires after some random amount of time. >> > >> > If that is reproducible, then please enable debugobjects. That should >> > pinpoint the culprit. >> >> It's net/smc. This recently had a similar bug with workqueues. >> (https://marc.info/?l=linux-kernel&m=148821582909541) fixed by >> 637fdbae60d6cb9f6e963c1079d7e0445c86ff7d > > Fixed? It's not fixed by that commit. The workqueue code merily got a new > WARN_ON_ONCE(). But the underlying problem is still unfixed in net/smc > >> so it's probably unsurprising that there are similar issues. > > That one is related to workqueues: > >> WARNING: CPU: 0 PID: 2430 at lib/debugobjects.c:289 > debug_print_object+0x87/0xb0 >> ODEBUG: free active (active state 0) object type: timer_list hint: > delayed_work_timer_fn+0x0/0x20 > > delayed_work_timer_fn() is what queues the work once the timer expires. > >> CPU: 0 PID: 2430 Comm: trinity-c4 Not tainted 4.11.0-rc3-think+ #3 >> Call Trace: >> dump_stack+0x68/0x93 >> __warn+0xcb/0xf0 >> warn_slowpath_fmt+0x5f/0x80 >> ? debug_check_no_obj_freed+0xd9/0x260 >> debug_print_object+0x87/0xb0 >> ? work_on_cpu+0xd0/0xd0 >> debug_check_no_obj_freed+0x219/0x260 >> ? __sk_destruct+0x10d/0x1c0 >> kmem_cache_free+0x9f/0x370 >> __sk_destruct+0x10d/0x1c0 >> sk_destruct+0x20/0x30 >> __sk_free+0x43/0xa0 >> sk_free+0x18/0x20 > > smc_release does at the end of the function: > > if (smc->use_fallback) { > schedule_delayed_work(&smc->sock_put_work, > TCP_TIMEWAIT_LEN); > } else if (sk->sk_state == SMC_CLOSED) { > smc_conn_free(&smc->conn); > schedule_delayed_work(&smc->sock_put_work, > SMC_CLOSE_SOCK_PUT_DELAY); > } > sk->sk_prot->unhash(sk); > release_sock(sk); > > sock_put(sk); > > sock_put(sk) > { > if (atomic_dec_and_test(&sk->sk_refcnt)) > sk_free(sk); > } > > That means either smc_release() queued delayed work or it was already > queued. > > But in neither case it holds an extra refcount on sk. Otherwise sock_put() > would not end up in sk_free(). We are working on a fix for the smc socket closing code right now. > > Thanks, > > tglx