Messages in this thread | | | Date | Mon, 15 Nov 2021 10:44:11 +0000 | From | Mark Rutland <> | Subject | Re: KASAN + CPU soft-hotplug = stack-out-of-bounds at cpuinfo_store_cpu |
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Hi,
On Fri, Nov 12, 2021 at 11:50:16PM -0500, Qian Cai wrote: > FYI, running CPU soft-hotplug with KASAN on arm64 defconfig will > always trigger a stack-out-of-bounds below. I am not right sure where > exactly KASAN pointed at, so I am just doing the brute-force > bisect. The progress so far:
From below it looks like this is on linux-next; I can reproduce this on v5.16-rc1 using your config, when hotplugging CPU0 back in.
We used to have issues with stale poison being left on the stack across a hotplug, and we fixed that with commit:
e1b77c92981a5222 ("sched/kasan: remove stale KASAN poison after hotplug")
... but it looks like we no longer call init_idle() for each hotplug since commit:
f1a0a376ca0c4ef1 ("sched/core: Initialize the idle task with preemption disabled")
... and so don't get the kasan_unpoison_task_stack() call which we want when bringing up a CPU, which we used to get by way of idle_thread_get() calling init_idle().
Adding a call to kasan_unpoison_task_stack(idle) within bringup_cpu() gets rid of that, and I reckon we want that explciitly *somewhere* on the CPU bringup path.
Thanks, Mark.
> # git bisect log > git bisect start > # bad: [e73f0f0ee7541171d89f2e2491130c7771ba58d3] Linux 5.14-rc1 > git bisect bad e73f0f0ee7541171d89f2e2491130c7771ba58d3 > # good: [62fb9874f5da54fdb243003b386128037319b219] Linux 5.13 > git bisect good 62fb9874f5da54fdb243003b386128037319b219 > # bad: [e058a84bfddc42ba356a2316f2cf1141974625c9] Merge tag 'drm-next-2021-07-01' of git://anongit.freedesktop.org/drm/drm > git bisect bad e058a84bfddc42ba356a2316f2cf1141974625c9 > # bad: [a6eaf3850cb171c328a8b0db6d3c79286a1eba9d] Merge tag 'sched-urgent-2021-06-30' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip > git bisect bad a6eaf3850cb171c328a8b0db6d3c79286a1eba9d > # bad: [31e798fd6f0ff0acdc49c1a358b581730936a09a] Merge tag 'media/v5.14-1' of git://git.kernel.org/pub/scm/linux/kernel/git/mchehab/linux-media > git bisect bad 31e798fd6f0ff0acdc49c1a358b581730936a09a > > I am going to test the "arm64-upstream" merge request next which has > some interesting arm64/cpuinfo patches. > > BUG: KASAN: stack-out-of-bounds in vsnprintf > Read of size 8 at addr ffff800016297db8 by task swapper/0/0
> > CPU: 0 PID: 0 Comm: swapper/0 Not tainted 5.15.0-next-20211110 #157 > Hardware name: MiTAC RAPTOR EV-883832-X3-0001/RAPTOR, BIOS 1.6 06/28/2020 > Call trace: > dump_backtrace > show_stack > dump_stack_lvl > print_address_description.constprop.0 > kasan_report > __asan_report_load8_noabort > vsnprintf > vsnprintf at /root/linux-next/lib/vsprintf.c:2807 > vprintk_store > vprintk_store at /root/linux-next/kernel/printk/printk.c:2138 (discriminator 5) > vprintk_emit > vprintk_emit at /root/linux-next/kernel/printk/printk.c:2232 > vprintk_default > vprintk_default at /root/linux-next/kernel/printk/printk.c:2260 > vprintk > vprintk at /root/linux-next/kernel/printk/printk_safe.c:50 > _printk > printk at /root/linux-next/kernel/printk/printk.c:2264 > __cpuinfo_store_cpu > __cpuinfo_store_cpu at /root/linux-next/arch/arm64/kernel/cpuinfo.c:412 > cpuinfo_store_cpu > cpuinfo_store_cpu at /root/linux-next/arch/arm64/kernel/cpuinfo.c:418 > secondary_start_kernel > secondary_start_kernel at /root/linux-next/arch/arm64/kernel/smp.c:241 > __secondary_switched > > > addr ffff800016297db8 is located in stack of task swapper/0/0 at offset 136 in frame: > _printk > > this frame has 1 object: > [32, 64) 'args' > > Memory state around the buggy address: > ffff800016297c80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 > ffff800016297d00: 00 00 00 00 00 00 f1 f1 f1 f1 00 00 00 00 f3 f3 > >ffff800016297d80: f3 f3 00 00 00 00 f3 f3 00 00 00 00 00 00 00 00 > ^ > ffff800016297e00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 > ffff800016297e80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
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