Re: [ 0.003333] BUG: KASAN: use-after-scope in console_unlock+0x605/0xcc0

Dmitry Vyukov
2017-11-30T08:16:44Z

On Thu, Nov 30, 2017 at 7:47 AM, Sergey Senozhatsky
<sergey.senozhatsky.work@gmail.com> wrote:
> Hi,
>
> On (11/30/17 10:26), Fengguang Wu wrote:
>> FYI this happens in mainline kernel v4.15-rc1 .
>> It shows up after v4.14 . Bisect is on the way.
>
> hm, printk saw no changes between 4.14 and 4.15
>
>
>> It occurs in 4 out of 4 boots.
>>
>> [ 0.003333] RCU callback double-/use-after-free debug enabled.
>> [ 0.003333] RCU CPU stall warnings timeout set to 100 (rcu_cpu_stall_timeout).
>> [ 0.003333] Tasks RCU enabled.
>> [ 0.003333] NR_IRQS: 4352, nr_irqs: 48, preallocated irqs: 16
>> [ 0.003333] ==================================================================
>> [ 0.003333] BUG: KASAN: use-after-scope in console_unlock+0x605/0xcc0:
>> atomic_read at arch/x86/include/asm/atomic.h:27
>> (inlined by) static_key_count at include/linux/jump_label.h:191
>> (inlined by) static_key_false at include/linux/jump_label.h:201
>> (inlined by) trace_console_rcuidle at include/trace/events/printk.h:10
>> (inlined by) call_console_drivers at kernel/printk/printk.c:1556
>> (inlined by) console_unlock at kernel/printk/printk.c:2233
>> [ 0.003333] Write of size 4 at addr ffffffff83607aa0 by task swapper/0
>> [ 0.003333]
>> [ 0.003333] CPU: 0 PID: 0 Comm: swapper Not tainted 4.15.0-rc1 #1
>> [ 0.003333] Call Trace:
>> [ 0.003333] ? print_address_description+0x4f/0x3c0:
>> print_address_description at mm/kasan/report.c:253
>> [ 0.003333] ? console_unlock+0x605/0xcc0:
>> atomic_read at arch/x86/include/asm/atomic.h:27
>> (inlined by) static_key_count at include/linux/jump_label.h:191
>> (inlined by) static_key_false at include/linux/jump_label.h:201
>> (inlined by) trace_console_rcuidle at include/trace/events/printk.h:10
>> (inlined by) call_console_drivers at kernel/printk/printk.c:1556
>> (inlined by) console_unlock at kernel/printk/printk.c:2233
>
> so KASAN didn't like atomic_read(&key->enabled) from static_key_count()?
> "Write of size 4"...
>
>
>> [ 0.003333] ? kasan_report+0x304/0x390:
>> kasan_report_error at mm/kasan/report.c:352
>> (inlined by) kasan_report at mm/kasan/report.c:409
>> [ 0.003333] ? console_unlock+0x605/0xcc0:
>> atomic_read at arch/x86/include/asm/atomic.h:27
>> (inlined by) static_key_count at include/linux/jump_label.h:191
>> (inlined by) static_key_false at include/linux/jump_label.h:201
>> (inlined by) trace_console_rcuidle at include/trace/events/printk.h:10
>> (inlined by) call_console_drivers at kernel/printk/printk.c:1556
>> (inlined by) console_unlock at kernel/printk/printk.c:2233
>> [ 0.003333] ? wake_up_klogd+0x180/0x180:
>> console_unlock at kernel/printk/printk.c:2138
>> [ 0.003333] ? _raw_spin_unlock_irqrestore+0xcf/0xf0:
>> __raw_spin_unlock_irqrestore at include/linux/spinlock_api_smp.h:161
>> (inlined by) _raw_spin_unlock_irqrestore at kernel/locking/spinlock.c:191
>> [ 0.003333] ? __down_trylock_console_sem+0xf8/0x120:
>> __down_trylock_console_sem at kernel/printk/printk.c:234
>> [ 0.003333] ? __down_trylock_console_sem+0x106/0x120:
>> __down_trylock_console_sem at kernel/printk/printk.c:235
>> [ 0.003333] ? vprintk_emit+0x63e/0x6f0:
>> vprintk_emit at kernel/printk/printk.c:1757
>> [ 0.003333] ? vprintk_func+0x11e/0x130:
>> vprintk_func at kernel/printk/printk_safe.c:379
>> [ 0.003333] ? printk+0xaf/0xcf:
>> printk at kernel/printk/printk.c:1824
>> [ 0.003333] ? show_regs_print_info+0x40/0x40:
>> printk at kernel/printk/printk.c:1824
>> [ 0.003333] ? __flush_tlb_all+0x1e/0x31:
>> __flush_tlb_global at arch/x86/include/asm/paravirt.h:298
>> (inlined by) __flush_tlb_all at arch/x86/include/asm/tlbflush.h:293
>> [ 0.003333] ? native_flush_tlb_global+0x5/0xa0:
>> native_flush_tlb_global at arch/x86/kernel/paravirt.c:199
>> [ 0.003333] ? kasan_init+0x276/0x306:
>> kasan_init at arch/x86/mm/kasan_init_64.c:349
>> [ 0.003333] ? setup_arch+0x1bb0/0x1cad:
>> setup_arch at arch/x86/kernel/setup.c:1236
>> [ 0.003333] ? reserve_standard_io_resources+0x88/0x88:
>> setup_arch at arch/x86/kernel/setup.c:829
>> [ 0.003333] ? vprintk_emit+0x6dc/0x6f0:
>> vprintk_emit at kernel/printk/printk.c:1761
>> [ 0.003333] ? vprintk_func+0x125/0x130:
>> vprintk_func at kernel/printk/printk_safe.c:380
>> [ 0.003333] ? printk+0xaf/0xcf:
>> printk at kernel/printk/printk.c:1824
>> [ 0.003333] ? show_regs_print_info+0x40/0x40:
>> printk at kernel/printk/printk.c:1824
>> [ 0.003333] ? trace_hardirqs_on+0x220/0x220:
>> trace_hardirqs_off at kernel/trace/trace_irqsoff.c:799
>> [ 0.003333] ? __early_make_pgtable+0x2a5/0x308:
>> __early_make_pgtable at arch/x86/kernel/head64.c:251
>> [ 0.003333] ? boot_cpu_init+0x16/0x56:
>> set_bit at arch/x86/include/asm/bitops.h:76
>> (inlined by) cpumask_set_cpu at include/linux/cpumask.h:297
>> (inlined by) set_cpu_online at include/linux/cpumask.h:799
>> (inlined by) boot_cpu_init at kernel/cpu.c:2012
>> [ 0.003333] ? start_kernel+0xe7/0x8cd:
>> add_latent_entropy at include/linux/random.h:26
>> (inlined by) start_kernel at init/main.c:535
>> [ 0.003333] ? thread_stack_cache_init+0x37/0x37
>> [ 0.003333] ? x86_cpuid_vendor+0xbe/0xd0:
>> x86_cpuid_vendor at arch/x86/include/asm/microcode.h:125
>> [ 0.003333] ? x86_family+0x2f/0x40:
>> x86_family at arch/x86/lib/cpu.c:14
>> [ 0.003333] ? load_ucode_bsp+0x3c4/0x46f:
>> load_ucode_bsp at arch/x86/kernel/cpu/microcode/core.c:189
>> [ 0.003333] ? x86_early_init_platform_quirks+0x146/0x1a1:
>> x86_early_init_platform_quirks at arch/x86/kernel/platform-quirks.c:31
>> [ 0.003333] ? secondary_startup_64+0xa5/0xb0:
>> secondary_startup_64 at arch/x86/kernel/head_64.S:237
>> [ 0.003333]
>> [ 0.003333] Memory state around the buggy address:
>> [ 0.003333] ffffffff83607980: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>> [ 0.003333] ffffffff83607a00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>> [ 0.003333] >ffffffff83607a80: f1 f1 f1 f1 f8 f2 f2 f2 f2 f2 f2 f2 00 f2 f2 f2
>
> to be honest, this backtrace hardly makes any sense to me.
>
> vprintk_emit()
> reserve_standard_io_resources()
> __flush_tlb_all()
> vprintk_emit()
> __down_trylock_console_sem()
> wake_up_klogd()
> console_unlock()
>
> I need some help here.

You can try dirty patch from here:
https://groups.google.com/d/msg/kasan-dev/iDb5bhcMBT0/55QzwWaHAwAJ
It should make KASAN print the exact variable name and frame where it
was allocated.