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Message-ID: <202509081409.2daadf50-lkp@intel.com>
Date: Mon, 8 Sep 2025 14:52:22 +0800
From: kernel test robot <oliver.sang@...el.com>
To: Joey Pabalinas <joeypabalinas@...il.com>
CC: <oe-lkp@...ts.linux.dev>, <lkp@...el.com>, <linux-kernel@...r.kernel.org>,
<linux-mm@...ck.org>, Kees Cook <kees@...nel.org>, Joey Pabalinas
<joeypabalinas@...il.com>, <oliver.sang@...el.com>
Subject: Re: [PATCH] fork: simplify overcomplicated if conditions
Hello,
kernel test robot noticed "BUG:kernel_NULL_pointer_dereference,address" on:
commit: 62b2846e29a8bec933d0dd7a3a4ccc7af409d8d0 ("[PATCH] fork: simplify overcomplicated if conditions")
url: https://github.com/intel-lab-lkp/linux/commits/Joey-Pabalinas/fork-simplify-overcomplicated-if-conditions/20250904-144729
base: https://git.kernel.org/cgit/linux/kernel/git/kees/linux.git for-next/execve
patch link: https://lore.kernel.org/all/357638f71edc7f1d9814b1851a64e09a8895bffc.1756968204.git.joeypabalinas@gmail.com/
patch subject: [PATCH] fork: simplify overcomplicated if conditions
in testcase: boot
config: i386-randconfig-004-20250906
compiler: gcc-13
test machine: qemu-system-x86_64 -enable-kvm -cpu SandyBridge -smp 2 -m 16G
(please refer to attached dmesg/kmsg for entire log/backtrace)
+---------------------------------------------+------------+------------+
| | 8c94db0ae9 | 62b2846e29 |
+---------------------------------------------+------------+------------+
| boot_successes | 6 | 0 |
| boot_failures | 0 | 6 |
| BUG:kernel_NULL_pointer_dereference,address | 0 | 6 |
| Oops | 0 | 6 |
| EIP:rest_init | 0 | 6 |
| Kernel_panic-not_syncing:Fatal_exception | 0 | 6 |
+---------------------------------------------+------------+------------+
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@...el.com>
| Closes: https://lore.kernel.org/oe-lkp/202509081409.2daadf50-lkp@intel.com
[ 3.204615][ T0] BUG: kernel NULL pointer dereference, address: 00000020
[ 3.205081][ T0] #PF: supervisor write access in kernel mode
[ 3.205081][ T0] #PF: error_code(0x0002) - not-present page
[ 3.205081][ T0] *pde = 00000000
[ 3.205081][ T0] Oops: Oops: 0002 [#1] SMP
[ 3.205081][ T0] CPU: 0 UID: 0 PID: 0 Comm: swapper/0 Not tainted 6.17.0-rc2-00004-g62b2846e29a8 #1 PREEMPT(full) cdac75d461890a0b0673a9c64f8f62c890a06589
[ 3.205081][ T0] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
[ 3.205081][ T0] EIP: rest_init (init/main.c:717)
[ 3.205081][ T0] Code: 00 75 1b b9 b4 d6 a7 83 ba 4a 03 00 00 b8 9b d6 a7 83 c6 05 25 19 68 84 01 e8 80 c8 7f fe 89 d8 ba c0 ab f6 83 e8 e0 aa 7c fe <81> 48 20 00 00 00 04 64 8b 3d 18 20 8d 84 89 c6 89 fb 83 e3 1f 43
All code
========
0: 00 75 1b add %dh,0x1b(%rbp)
3: b9 b4 d6 a7 83 mov $0x83a7d6b4,%ecx
8: ba 4a 03 00 00 mov $0x34a,%edx
d: b8 9b d6 a7 83 mov $0x83a7d69b,%eax
12: c6 05 25 19 68 84 01 movb $0x1,-0x7b97e6db(%rip) # 0xffffffff8468193e
19: e8 80 c8 7f fe call 0xfffffffffe7fc89e
1e: 89 d8 mov %ebx,%eax
20: ba c0 ab f6 83 mov $0x83f6abc0,%edx
25: e8 e0 aa 7c fe call 0xfffffffffe7cab0a
2a:* 81 48 20 00 00 00 04 orl $0x4000000,0x20(%rax) <-- trapping instruction
31: 64 8b 3d 18 20 8d 84 mov %fs:-0x7b72dfe8(%rip),%edi # 0xffffffff848d2050
38: 89 c6 mov %eax,%esi
3a: 89 fb mov %edi,%ebx
3c: 83 e3 1f and $0x1f,%ebx
3f: 43 rex.XB
Code starting with the faulting instruction
===========================================
0: 81 48 20 00 00 00 04 orl $0x4000000,0x20(%rax)
7: 64 8b 3d 18 20 8d 84 mov %fs:-0x7b72dfe8(%rip),%edi # 0xffffffff848d2026
e: 89 c6 mov %eax,%esi
10: 89 fb mov %edi,%ebx
12: 83 e3 1f and $0x1f,%ebx
15: 43 rex.XB
[ 3.205081][ T0] EAX: 00000000 EBX: ffffffea ECX: 00000000 EDX: 00000000
[ 3.205081][ T0] ESI: ee7fd750 EDI: ee7fd740 EBP: 83eebf80 ESP: 83eebf74
[ 3.205081][ T0] DS: 007b ES: 007b FS: 00d8 GS: 0000 SS: 0068 EFLAGS: 00210246
[ 3.205081][ T0] CR0: 80050033 CR2: 00000020 CR3: 04910000 CR4: 00040690
[ 3.205081][ T0] Call Trace:
[ 3.205081][ T0] start_kernel (init/main.c:1335)
[ 3.205081][ T0] i386_start_kernel (arch/x86/kernel/head32.c:129)
[ 3.205081][ T0] startup_32_smp (arch/x86/kernel/head_32.S:290)
[ 3.205081][ T0] Modules linked in:
[ 3.205081][ T0] CR2: 0000000000000020
[ 3.205081][ T0] ---[ end trace 0000000000000000 ]---
[ 3.205081][ T0] EIP: rest_init (init/main.c:717)
[ 3.205081][ T0] Code: 00 75 1b b9 b4 d6 a7 83 ba 4a 03 00 00 b8 9b d6 a7 83 c6 05 25 19 68 84 01 e8 80 c8 7f fe 89 d8 ba c0 ab f6 83 e8 e0 aa 7c fe <81> 48 20 00 00 00 04 64 8b 3d 18 20 8d 84 89 c6 89 fb 83 e3 1f 43
All code
========
0: 00 75 1b add %dh,0x1b(%rbp)
3: b9 b4 d6 a7 83 mov $0x83a7d6b4,%ecx
8: ba 4a 03 00 00 mov $0x34a,%edx
d: b8 9b d6 a7 83 mov $0x83a7d69b,%eax
12: c6 05 25 19 68 84 01 movb $0x1,-0x7b97e6db(%rip) # 0xffffffff8468193e
19: e8 80 c8 7f fe call 0xfffffffffe7fc89e
1e: 89 d8 mov %ebx,%eax
20: ba c0 ab f6 83 mov $0x83f6abc0,%edx
25: e8 e0 aa 7c fe call 0xfffffffffe7cab0a
2a:* 81 48 20 00 00 00 04 orl $0x4000000,0x20(%rax) <-- trapping instruction
31: 64 8b 3d 18 20 8d 84 mov %fs:-0x7b72dfe8(%rip),%edi # 0xffffffff848d2050
38: 89 c6 mov %eax,%esi
3a: 89 fb mov %edi,%ebx
3c: 83 e3 1f and $0x1f,%ebx
3f: 43 rex.XB
Code starting with the faulting instruction
===========================================
0: 81 48 20 00 00 00 04 orl $0x4000000,0x20(%rax)
7: 64 8b 3d 18 20 8d 84 mov %fs:-0x7b72dfe8(%rip),%edi # 0xffffffff848d2026
e: 89 c6 mov %eax,%esi
10: 89 fb mov %edi,%ebx
12: 83 e3 1f and $0x1f,%ebx
15: 43 rex.XB
The kernel config and materials to reproduce are available at:
https://download.01.org/0day-ci/archive/20250908/202509081409.2daadf50-lkp@intel.com
--
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki
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