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Date: Tue, 30 Jan 2024 22:09:38 +0800
From: Oliver Sang <oliver.sang@intel.com>
To: Abel Wu <wuyun.abel@bytedance.com>
CC: <oe-lkp@lists.linux.dev>, <lkp@intel.com>, <linux-kernel@vger.kernel.org>,
	Peter Zijlstra <peterz@infradead.org>, <aubrey.li@linux.intel.com>,
	<yu.c.chen@intel.com>, Tiwei Bie <tiwei.btw@antgroup.com>,
	<oliver.sang@intel.com>
Subject: Re: [linus:master] [sched/eevdf] 2227a957e1:
 BUG:kernel_NULL_pointer_dereference,address
Message-ID: <ZbkDIlIR7qzPt7Vk@xsang-OptiPlex-9020>
References: <202401301012.2ed95df0-oliver.sang@intel.com>
 <23cbb613-c8a2-4f07-b83b-fa3104bef642@bytedance.com>
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hi, Abel,

On Tue, Jan 30, 2024 at 06:13:32PM +0800, Abel Wu wrote:
> On 1/30/24 3:24 PM, kernel test robot Wrote:
> > 
> > 
> > Hello,
> > 
> > (besides a previous performance report),
> > kernel test robot noticed "BUG:kernel_NULL_pointer_dereference,address" on:
> > 
> > commit: 2227a957e1d5b1941be4e4207879ec74f4bb37f8 ("sched/eevdf: Sort the rbtree by virtual deadline")
> > https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git master
> > 
> > [test failed on linus/master 3a5879d495b226d0404098e3564462d5f1daa33b]
> > [test failed on linux-next/master 01af33cc9894b4489fb68fa35c40e9fe85df63dc]
> > 
> > in testcase: trinity
> > version: trinity-i386-abe9de86-1_20230429
> > with following parameters:
> > 
> > 	runtime: 300s
> > 	group: group-03
> > 	nr_groups: 5
> > 
> > test-description: Trinity is a linux system call fuzz tester.
> > test-url: http://codemonkey.org.uk/projects/trinity/
> > 
> > 
> > compiler: clang-17
> > test machine: qemu-system-x86_64 -enable-kvm -cpu SandyBridge -smp 2 -m 16G
> > 
> > (please refer to attached dmesg/kmsg for entire log/backtrace)
> > 
> > 
> > 
> > we found this issue happens in very random way (23 out of 999 runs).
> > but keeps clean on parent.
> 
> Thanks for reporting, I will try to reproduce the issue. Does the 'parent'
> mean the same code branch without this commit?


it just means the parent in git log.

xsang@inn:/c/repo/linux$ git log --oneline --graph 2227a957e1
* 2227a957e1d5b sched/eevdf: Sort the rbtree by virtual deadline
* 84db47ca7146d sched/numa: Fix mm numa_scan_seq based unconditional scan  <-- parent


> 
> > 
> > 84db47ca7146d7bd 2227a957e1d5b1941be4e420787
> > ---------------- ---------------------------
> >         fail:runs  %reproduction    fail:runs
> >             |             |             |
> >             :999          2%          23:999   dmesg.BUG:kernel_NULL_pointer_dereference,address
> >             :999          2%          23:999   dmesg.Kernel_panic-not_syncing:Fatal_exception
> >             :999          2%          23:999   dmesg.Oops:#[##]
> > 
> > 
> > 
> > 
> > If you fix the issue in a separate patch/commit (i.e. not just a new version of
> > the same patch/commit), kindly add following tags
> > | Reported-by: kernel test robot <oliver.sang@intel.com>
> > | Closes: https://lore.kernel.org/oe-lkp/202401301012.2ed95df0-oliver.sang@intel.com
> > 
> > 
> > sorry for below parse failure which caused no real line numbers.
> > we will follow further. the orgial dmesg could be fetch from below link.
> > 
> > 
> > [  512.079810][ T8305] BUG: kernel NULL pointer dereference, address: 0000002c
> > [  512.080897][ T8305] #PF: supervisor read access in kernel mode
> > [  512.081636][ T8305] #PF: error_code(0x0000) - not-present page
> > [  512.082337][ T8305] *pde = 00000000
> > [  512.082829][ T8305] Oops: 0000 [#1] PREEMPT SMP
> > [  512.083407][ T8305] CPU: 1 PID: 8305 Comm: watchdog Tainted: G        W        N 6.7.0-rc1-00006-g2227a957e1d5 #1 819e6d1a8b887f5f97adb4aed77d98b15504c836
> > [  512.084986][ T8305] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
> > [ 512.086203][ T8305] EIP: set_next_entity (fair.c:?)
> 
> There was actually a NULL-test in pick_eevdf() before this commit,
> but I removed it by intent as I found it impossible to be NULL after
> examining 'all' the cases.
> 
> Also cc Tiwei who once proposed to add this check back.
> https://lore.kernel.org/all/20231208112100.18141-1-tiwei.btw@antgroup.com/
> 
> Thanks,
> 	Abel
> 
> > [ 512.086881][ T8305] Code: 89 d6 89 cf 85 d2 74 22 39 77 58 75 1d 89 f0 90 90 90 90 90 8b 48 70 39 41 58 75 0e c7 41 58 00 00 00 00 8b 40 6c 85 c0 75 ea <83> 7e 2c 00 74 28 3e 8d 74 26 00 89 f9 89 f2 e8 36 59 00 00 89 f9
> > All code
> > ========
> >     0:	89 d6                	mov    %edx,%esi
> >     2:	89 cf                	mov    %ecx,%edi
> >     4:	85 d2                	test   %edx,%edx
> >     6:	74 22                	je     0x2a
> >     8:	39 77 58             	cmp    %esi,0x58(%rdi)
> >     b:	75 1d                	jne    0x2a
> >     d:	89 f0                	mov    %esi,%eax
> >     f:	90                   	nop
> >    10:	90                   	nop
> >    11:	90                   	nop
> >    12:	90                   	nop
> >    13:	90                   	nop
> >    14:	8b 48 70             	mov    0x70(%rax),%ecx
> >    17:	39 41 58             	cmp    %eax,0x58(%rcx)
> >    1a:	75 0e                	jne    0x2a
> >    1c:	c7 41 58 00 00 00 00 	movl   $0x0,0x58(%rcx)
> >    23:	8b 40 6c             	mov    0x6c(%rax),%eax
> >    26:	85 c0                	test   %eax,%eax
> >    28:	75 ea                	jne    0x14
> >    2a:*	83 7e 2c 00          	cmpl   $0x0,0x2c(%rsi)		<-- trapping instruction
> >    2e:	74 28                	je     0x58
> >    30:	3e 8d 74 26 00       	lea    %ds:0x0(%rsi,%riz,1),%esi
> >    35:	89 f9                	mov    %edi,%ecx
> >    37:	89 f2                	mov    %esi,%edx
> >    39:	e8 36 59 00 00       	callq  0x5974
> >    3e:	89 f9                	mov    %edi,%ecx
> > 
> > Code starting with the faulting instruction
> > ===========================================
> >     0:	83 7e 2c 00          	cmpl   $0x0,0x2c(%rsi)
> >     4:	74 28                	je     0x2e
> >     6:	3e 8d 74 26 00       	lea    %ds:0x0(%rsi,%riz,1),%esi
> >     b:	89 f9                	mov    %edi,%ecx
> >     d:	89 f2                	mov    %esi,%edx
> >     f:	e8 36 59 00 00       	callq  0x594a
> >    14:	89 f9                	mov    %edi,%ecx
> > [  512.089261][ T8305] EAX: 00000000 EBX: e75ff100 ECX: e75ff100 EDX: 00000000
> > [  512.090180][ T8305] ESI: 00000000 EDI: e75ff100 EBP: ed229dd0 ESP: ed229dc0
> > [  512.091097][ T8305] DS: 007b ES: 007b FS: 00d8 GS: 0033 SS: 0068 EFLAGS: 00010046
> > [  512.092138][ T8305] CR0: 80050033 CR2: 0000002c CR3: 0a508000 CR4: 000406d0
> > [  512.093076][ T8305] DR0: 00000000 DR1: 00000000 DR2: 00000000 DR3: 00000000
> > [  512.094004][ T8305] DR6: fffe0ff0 DR7: 00000400
> > [  512.094643][ T8305] Call Trace:
> > [ 512.095145][ T8305] ? __die_body (dumpstack.c:?)
> > [ 512.095755][ T8305] ? __die (??:?)
> > [ 512.096309][ T8305] ? page_fault_oops (fault.c:?)
> > [ 512.096994][ T8305] ? __lock_acquire (lockdep.c:?)
> > [ 512.097677][ T8305] ? kmemleak_alloc (??:?)
> > [ 512.098343][ T8305] ? kernelmode_fixup_or_oops (fault.c:?)
> > [ 512.099085][ T8305] ? __bad_area_nosemaphore (fault.c:?)
> > [ 512.099839][ T8305] ? bad_area_nosemaphore (fault.c:?)
> > [ 512.100579][ T8305] ? do_user_addr_fault (fault.c:?)
> > [ 512.101325][ T8305] ? exc_page_fault (??:?)
> > [ 512.101992][ T8305] ? pvclock_clocksource_read_nowd (??:?)
> > [ 512.102799][ T8305] ? handle_exception (init_task.c:?)
> > [ 512.103492][ T8305] ? yield_to_task_fair (fair.c:?)
> > [ 512.104166][ T8305] ? pvclock_clocksource_read_nowd (??:?)
> > [ 512.104975][ T8305] ? set_next_entity (fair.c:?)
> > [ 512.105655][ T8305] ? pvclock_clocksource_read_nowd (??:?)
> > [ 512.106447][ T8305] ? set_next_entity (fair.c:?)
> > [ 512.107106][ T8305] pick_next_task_fair (??:?)
> > [ 512.107788][ T8305] ? put_prev_task_rt (build_policy.c:?)
> > [ 512.108460][ T8305] __pick_next_task_fair (fair.c:?)
> > [ 512.109162][ T8305] __schedule (core.c:?)
> > [ 512.109753][ T8305] schedule (??:?)
> > [ 512.110284][ T8305] do_nanosleep (hrtimer.c:?)
> > [ 512.110900][ T8305] hrtimer_nanosleep (??:?)
> > [ 512.111581][ T8305] ? __remove_hrtimer (hrtimer.c:?)
> > [ 512.112264][ T8305] common_nsleep (posix-timers.c:?)
> > [ 512.112891][ T8305] __ia32_sys_clock_nanosleep (??:?)
> > [ 512.113657][ T8305] ? syscall_enter_from_user_mode_work (??:?)
> > [ 512.114486][ T8305] __do_fast_syscall_32 (common.c:?)
> > [ 512.115180][ T8305] ? irqentry_exit_to_user_mode (??:?)
> > [ 512.115936][ T8305] ? irqentry_exit_to_user_mode (??:?)
> > [ 512.116690][ T8305] do_fast_syscall_32 (??:?)
> > [ 512.117386][ T8305] do_SYSENTER_32 (??:?)
> > [ 512.118022][ T8305] entry_SYSENTER_32 (??:?)
> > [  512.118645][ T8305] EIP: 0xb7edf539
> > [ 512.119172][ T8305] Code: 03 74 b4 01 10 07 03 74 b0 01 10 08 03 74 d8 01 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 51 52 55 89 e5 0f 34 cd 80 <5d> 5a 59 c3 90 90 90 90 0f 1f 00 58 b8 77 00 00 00 cd 80 90 0f 1f
> > All code
> > ========
> >     0:	03 74 b4 01          	add    0x1(%rsp,%rsi,4),%esi
> >     4:	10 07                	adc    %al,(%rdi)
> >     6:	03 74 b0 01          	add    0x1(%rax,%rsi,4),%esi
> >     a:	10 08                	adc    %cl,(%rax)
> >     c:	03 74 d8 01          	add    0x1(%rax,%rbx,8),%esi
> > 	...
> >    20:	00 51 52             	add    %dl,0x52(%rcx)
> >    23:	55                   	push   %rbp
> >    24:*	89 e5                	mov    %esp,%ebp		<-- trapping instruction
> >    26:	0f 34                	sysenter
> >    28:	cd 80                	int    $0x80
> >    2a:	5d                   	pop    %rbp
> >    2b:	5a                   	pop    %rdx
> >    2c:	59                   	pop    %rcx
> >    2d:	c3                   	retq
> >    2e:	90                   	nop
> >    2f:	90                   	nop
> >    30:	90                   	nop
> >    31:	90                   	nop
> >    32:	0f 1f 00             	nopl   (%rax)
> >    35:	58                   	pop    %rax
> >    36:	b8 77 00 00 00       	mov    $0x77,%eax
> >    3b:	cd 80                	int    $0x80
> >    3d:	90                   	nop
> >    3e:	0f                   	.byte 0xf
> >    3f:	1f                   	(bad)
> > 
> > Code starting with the faulting instruction
> > ===========================================
> >     0:	5d                   	pop    %rbp
> >     1:	5a                   	pop    %rdx
> >     2:	59                   	pop    %rcx
> >     3:	c3                   	retq
> >     4:	90                   	nop
> >     5:	90                   	nop
> >     6:	90                   	nop
> >     7:	90                   	nop
> >     8:	0f 1f 00             	nopl   (%rax)
> >     b:	58                   	pop    %rax
> >     c:	b8 77 00 00 00       	mov    $0x77,%eax
> >    11:	cd 80                	int    $0x80
> >    13:	90                   	nop
> >    14:	0f                   	.byte 0xf
> >    15:	1f                   	(bad)
> > 
> > 
> > The kernel config and materials to reproduce are available at:
> > https://download.01.org/0day-ci/archive/20240130/202401301012.2ed95df0-oliver.sang@intel.com
> > 
> > 
> >