Re: general protection fault, probably for non-canonical address in pick_next_task_fair()

[Abel Wu <wuyun.abel@bytedance.com>]

(+ Chen Yu, Oliver Sang)

On 2/29/24 11:55 PM, Breno Leitao Wrote:
> I've been running some stress test using stress-ng with a kernel with some
> debug options enabled, such as KASAN and friends (See the config below).
> 
> I saw it in rc4 and the decode instructions are a bit off (as it is here
> also - search for mavabs in dmesg below and you will find something as `(bad)`,
> so I though it was a machine issue. But now I see it again, and I am sharing
> for awareness.
> 
> This is happening in upstream kernel against the following commit
> d206a76d7d2726 ("Linux 6.8-rc6")
> 
> This is the exercpt that shows before the crash:
> 
> 	general protection fault, probably for non-canonical address 0xdffffc0000000014: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC KASAN
> 	KASAN: null-ptr-deref in range [0x00000000000000a0-0x00000000000000a7]
> 
> This is the stack that is getting it
> 
> 	? __die_body (arch/x86/kernel/dumpstack.c:421)
> 	? die_addr (arch/x86/kernel/dumpstack.c:460)
> 	? exc_general_protection (arch/x86/kernel/traps.c:? arch/x86/kernel/traps.c:643)
> 	? asm_exc_general_protection (arch/x86/include/asm/idtentry.h:564)
> 	? pick_next_task_fair (kernel/sched/sched.h:1453 kernel/sched/fair.c:8435)
> 	? pick_next_task_fair (kernel/sched/fair.c:5463 kernel/sched/fair.c:8434)
> 	? update_rq_clock_task (kernel/sched/core.c:?)
> 	__schedule (kernel/sched/core.c:6022 kernel/sched/core.c:6545 kernel/sched/core.c:6691)
> 	schedule (kernel/sched/core.c:6803 kernel/sched/core.c:6817)
> 	syscall_exit_to_user_mode (kernel/entry/common.c:98 include/linux/entry-common.h:328 kernel/entry/common.c:201 kernel/entry/common.c:212)
> 	do_syscall_64 (arch/x86/entry/common.c:102)
> 	? irqentry_exit_to_user_mode (kernel/entry/common.c:228)
> 	entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:129)
> 
> Full dmesg: https://paste.mozilla.org/RiLnt4QO#
> Configs: https://paste.mozilla.org/XJ9wbdRp
>