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

Sergey Senozhatsky
2017-11-30T06:47:18Z

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.

-ss