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Mon, 11 Oct 2021 07:42:30 -0700 (PDT) Date: Mon, 11 Oct 2021 16:42:29 +0200 From: Andrea Righi To: Marco Elver Cc: Dmitry Vyukov , Alexander Potapenko , kasan-dev@googlegroups.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: BUG: soft lockup in __kmalloc_node() with KFENCE enabled Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Authentication-Results: imf09.hostedemail.com; dkim=pass header.d=canonical.com header.s=20210705 header.b=uv89gm8O; spf=pass (imf09.hostedemail.com: domain of andrea.righi@canonical.com designates 185.125.188.123 as permitted sender) smtp.mailfrom=andrea.righi@canonical.com; dmarc=pass (policy=none) header.from=canonical.com X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: E130E30008F8 X-Stat-Signature: xwozh1whwr3n4sjtkob6r37rmd14w8ep X-HE-Tag: 1633963353-914162 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Mon, Oct 11, 2021 at 12:03:52PM +0200, Marco Elver wrote: > On Mon, 11 Oct 2021 at 11:53, Andrea Righi wrote: > > On Mon, Oct 11, 2021 at 11:23:32AM +0200, Andrea Righi wrote: > > ... > > > > You seem to use the default 20s stall timeout. FWIW syzbot uses 160 > > > > secs timeout for TCG emulation to avoid false positive warnings: > > > > https://github.com/google/syzkaller/blob/838e7e2cd9228583ca33c49a39aea4d863d3e36d/dashboard/config/linux/upstream-arm64-kasan.config#L509 > > > > There are a number of other timeouts raised as well, some as high as > > > > 420 seconds. > > > > > > I see, I'll try with these settings and see if I can still hit the soft > > > lockup messages. > > > > Still getting soft lockup messages even with the new timeout settings: > > > > [ 462.663766] watchdog: BUG: soft lockup - CPU#2 stuck for 430s! [systemd-udevd:168] > > [ 462.755758] watchdog: BUG: soft lockup - CPU#3 stuck for 430s! [systemd-udevd:171] > > [ 924.663765] watchdog: BUG: soft lockup - CPU#2 stuck for 861s! [systemd-udevd:168] > > [ 924.755767] watchdog: BUG: soft lockup - CPU#3 stuck for 861s! [systemd-udevd:171] > > The lockups are expected if you're hitting the TCG bug I linked. Try > to pass '-enable-kvm' to the inner qemu instance (my bad if you > already have), assuming that's somehow easy to do. If I add '-enable-kvm' I can triggering other random panics (almost immediately), like this one for example: [21383.189976] BUG: kernel NULL pointer dereference, address: 0000000000000098 [21383.190633] #PF: supervisor read access in kernel mode [21383.191072] #PF: error_code(0x0000) - not-present page [21383.191529] PGD 0 P4D 0 [21383.191771] Oops: 0000 [#1] SMP NOPTI [21383.192113] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 5.15-rc4 [21383.192757] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.14.0-2 04/01/2014 [21383.193414] RIP: 0010:wb_timer_fn+0x44/0x3c0 [21383.193855] Code: 41 8b 9c 24 98 00 00 00 41 8b 94 24 b8 00 00 00 41 8b 84 24 d8 00 00 00 4d 8b 74 24 28 01 d3 01 c3 49 8b 44 24 60 48 8b 40 78 <4c> 8b b8 98 00 00 00 4d 85 f6 0f 84 c4 00 00 00 49 83 7c 24 30 00 [21383.195366] RSP: 0018:ffffbcd140003e68 EFLAGS: 00010246 [21383.195842] RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000004 [21383.196425] RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffff9a3521f4fd80 [21383.197010] RBP: ffffbcd140003e90 R08: 0000000000000000 R09: 0000000000000000 [21383.197594] R10: 0000000000000004 R11: 000000000000000f R12: ffff9a34c75c4900 [21383.198178] R13: ffff9a34c3906de0 R14: 0000000000000000 R15: ffff9a353dc18c00 [21383.198763] FS: 0000000000000000(0000) GS:ffff9a353dc00000(0000) knlGS:0000000000000000 [21383.199558] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [21383.200212] CR2: 0000000000000098 CR3: 0000000005f54000 CR4: 00000000000006f0 [21383.200930] Call Trace: [21383.201210] [21383.201461] ? blk_stat_free_callback_rcu+0x30/0x30 [21383.202692] blk_stat_timer_fn+0x138/0x140 [21383.203180] call_timer_fn+0x2b/0x100 [21383.203666] __run_timers.part.0+0x1d1/0x240 [21383.204227] ? kvm_clock_get_cycles+0x11/0x20 [21383.204815] ? ktime_get+0x3e/0xa0 [21383.205309] ? native_apic_msr_write+0x2c/0x30 [21383.205914] ? lapic_next_event+0x20/0x30 [21383.206412] ? clockevents_program_event+0x94/0xf0 [21383.206873] run_timer_softirq+0x2a/0x50 [21383.207260] __do_softirq+0xcb/0x26f [21383.207647] irq_exit_rcu+0x8c/0xb0 [21383.208010] sysvec_apic_timer_interrupt+0x7c/0x90 [21383.208464] [21383.208713] asm_sysvec_apic_timer_interrupt+0x12/0x20 I think that systemd autotest used to use -enable-kvm, but then they removed it, because it was introducing too many problems in the nested KVM context. I'm not sure about the nature of those problems though, I can investigate a bit and see if I can understand what they were exactly. -Andrea