Re: [linus:master] [sched/eevdf] 2227a957e1: BUG:kernel_NULL_pointer_dereference,address

From: Abel Wu
Date: Tue Jan 30 2024 - 05:14:04 EST

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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?

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@xxxxxxxxx>
| Closes: https://lore.kernel.org/oe-lkp/202401301012.2ed95df0-oliver.sang@xxxxxxxxx

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@xxxxxxxxxxxx/

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@xxxxxxxxx

Next message: Luis Henriques: "[PATCH v3] keys: update key quotas in key_put()"
Previous message: Mika Westerberg: "Re: [PATCH 1/2] ata: ahci: Add force LPM policy quirk for ASUS B1400CEAE"
In reply to: kernel test robot: "[linus:master] [sched/eevdf] 2227a957e1: BUG:kernel_NULL_pointer_dereference,address"
Next in thread: Oliver Sang: "Re: [linus:master] [sched/eevdf] 2227a957e1: BUG:kernel_NULL_pointer_dereference,address"
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