UBSAN: array-index-out-of-bounds in __unfreeze_partials

Status: premoderation: reported syz repro on 2026/10/14 04:26
Bug presence: origin:downstream
[Documentation on labels]
Reported-by: syzbot+6a4b278fc45ab85758ad@syzkaller.appspotmail.com
First crash: 1d15h, last: 1d15h
▶ ▼ Bug presence (3)
Date Name Commit Repro Result
2026/10/15 android13-5.15-lts (ToT) ff23d765b06f syz [report] UBSAN: array-index-out-of-bounds in dup_fd
2026/10/15 lts (merge base) 2a5f794b8be1 syz Didn't crash
2026/10/15 upstream (ToT) 0fcb05b72344 syz Didn't crash

Sample crash report:
================================================================================
UBSAN: array-index-out-of-bounds in kernel/locking/qspinlock.c:130:9
index 3079 is out of range for type 'unsigned long[8]'
CPU: 0 PID: 746 Comm: syz.3.369 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
Call Trace:
 <TASK>
 __dump_stack+0x21/0x30 lib/dump_stack.c:88
 dump_stack_lvl+0x110/0x170 lib/dump_stack.c:106
 dump_stack+0x15/0x20 lib/dump_stack.c:113
 ubsan_epilogue+0xe/0x40 lib/ubsan.c:151
 __ubsan_handle_out_of_bounds+0xdf/0xf0 lib/ubsan.c:282
 decode_tail kernel/locking/qspinlock.c:130 [inline]
 __pv_queued_spin_lock_slowpath+0x90e/0x9b0 kernel/locking/qspinlock.c:468
 pv_queued_spin_lock_slowpath arch/x86/include/asm/paravirt.h:585 [inline]
 queued_spin_lock_slowpath+0x47/0x50 arch/x86/include/asm/qspinlock.h:51
 queued_spin_lock include/asm-generic/qspinlock.h:85 [inline]
 do_raw_spin_lock_flags include/linux/spinlock.h:200 [inline]
 __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:119 [inline]
 _raw_spin_lock_irqsave+0x120/0x130 kernel/locking/spinlock.c:162
 __unfreeze_partials+0x70/0x190 mm/slub.c:2496
 put_cpu_partial+0xc6/0x120 mm/slub.c:2612
 __slab_free+0x1d4/0x290 mm/slub.c:3395
 do_slab_free mm/slub.c:3514 [inline]
 ___cache_free+0x104/0x120 mm/slub.c:3535
 qlink_free+0x4d/0x90 mm/kasan/quarantine.c:157
 qlist_free_all+0x5f/0xb0 mm/kasan/quarantine.c:176
 kasan_quarantine_reduce+0x14a/0x170 mm/kasan/quarantine.c:283
 __kasan_slab_alloc+0x2f/0xe0 mm/kasan/common.c:443
 kasan_slab_alloc include/linux/kasan.h:217 [inline]
 slab_post_alloc_hook+0x4f/0x2b0 mm/slab.h:550
 slab_alloc_node mm/slub.c:3245 [inline]
 slab_alloc mm/slub.c:3255 [inline]
 kmem_cache_alloc+0xf7/0x260 mm/slub.c:3260
 kmem_cache_zalloc include/linux/slab.h:740 [inline]
 __alloc_file+0x28/0x2a0 fs/file_table.c:132
 alloc_empty_file+0x97/0x180 fs/file_table.c:181
 path_openat+0xf4/0x2f80 fs/namei.c:3736
 do_filp_open+0x1df/0x400 fs/namei.c:3777
 do_sys_openat2+0x15e/0x7f0 fs/open.c:1236
 do_sys_open fs/open.c:1252 [inline]
 __do_sys_openat fs/open.c:1268 [inline]
 __se_sys_openat fs/open.c:1263 [inline]
 __x64_sys_openat+0x136/0x160 fs/open.c:1263
 x64_sys_call+0x219/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:258
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7fda944122d9
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffd458db048 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00007fda94699fa0 RCX: 00007fda944122d9
RDX: 0000000000000000 RSI: 0000200000000000 RDI: ffffffffffffff9c
RBP: 00007fda944a9888 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000002 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fda94699fac R14: 00007fda94699fa0 R15: 00007fda94699fa0
 </TASK>
================================================================================
general protection fault, probably for non-canonical address 0xdffffc00001ff507: 0000 [#1] PREEMPT SMP KASAN
KASAN: probably user-memory-access in range [0x0000000000ffa838-0x0000000000ffa83f]
CPU: 0 PID: 746 Comm: syz.3.369 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
RIP: 0010:__pv_queued_spin_lock_slowpath+0x290/0x9b0 kernel/locking/qspinlock.c:471
Code: c8 48 c1 e8 03 42 80 3c 28 00 74 14 48 89 4c 24 20 48 8b 7c 24 20 e8 2f 4b 59 00 48 8b 4c 24 20 4c 03 39 4c 89 f8 48 c1 e8 03 <42> 80 3c 28 00 4d 89 fd 4c 8b 7c 24 28 74 08 4c 89 ef e8 a9 4b 59
RSP: 0018:ffffc90001daf260 EFLAGS: 00010002
RAX: 00000000001ff507 RBX: ffff88810006c000 RCX: ffffffff85ea2878
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 00000000ffffffff
RBP: ffffc90001daf350 R08: 0000000000000003 R09: 0000000000000004
R10: dffffc0000000000 R11: fffffbfff0e1904c R12: 1ffff1103ee07151
R13: dffffc0000000000 R14: 1ffff1102000d800 R15: 0000000000ffa838
FS:  000055556bb45500(0000) GS:ffff8881f7000000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000200000004002 CR3: 000000012d4f1000 CR4: 00000000003506b0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 pv_queued_spin_lock_slowpath arch/x86/include/asm/paravirt.h:585 [inline]
 queued_spin_lock_slowpath+0x47/0x50 arch/x86/include/asm/qspinlock.h:51
 queued_spin_lock include/asm-generic/qspinlock.h:85 [inline]
 do_raw_spin_lock_flags include/linux/spinlock.h:200 [inline]
 __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:119 [inline]
 _raw_spin_lock_irqsave+0x120/0x130 kernel/locking/spinlock.c:162
 __unfreeze_partials+0x70/0x190 mm/slub.c:2496
 put_cpu_partial+0xc6/0x120 mm/slub.c:2612
 __slab_free+0x1d4/0x290 mm/slub.c:3395
 do_slab_free mm/slub.c:3514 [inline]
 ___cache_free+0x104/0x120 mm/slub.c:3535
 qlink_free+0x4d/0x90 mm/kasan/quarantine.c:157
 qlist_free_all+0x5f/0xb0 mm/kasan/quarantine.c:176
 kasan_quarantine_reduce+0x14a/0x170 mm/kasan/quarantine.c:283
 __kasan_slab_alloc+0x2f/0xe0 mm/kasan/common.c:443
 kasan_slab_alloc include/linux/kasan.h:217 [inline]
 slab_post_alloc_hook+0x4f/0x2b0 mm/slab.h:550
 slab_alloc_node mm/slub.c:3245 [inline]
 slab_alloc mm/slub.c:3255 [inline]
 kmem_cache_alloc+0xf7/0x260 mm/slub.c:3260
 kmem_cache_zalloc include/linux/slab.h:740 [inline]
 __alloc_file+0x28/0x2a0 fs/file_table.c:132
 alloc_empty_file+0x97/0x180 fs/file_table.c:181
 path_openat+0xf4/0x2f80 fs/namei.c:3736
 do_filp_open+0x1df/0x400 fs/namei.c:3777
 do_sys_openat2+0x15e/0x7f0 fs/open.c:1236
 do_sys_open fs/open.c:1252 [inline]
 __do_sys_openat fs/open.c:1268 [inline]
 __se_sys_openat fs/open.c:1263 [inline]
 __x64_sys_openat+0x136/0x160 fs/open.c:1263
 x64_sys_call+0x219/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:258
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7fda944122d9
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffd458db048 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00007fda94699fa0 RCX: 00007fda944122d9
RDX: 0000000000000000 RSI: 0000200000000000 RDI: ffffffffffffff9c
RBP: 00007fda944a9888 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000002 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fda94699fac R14: 00007fda94699fa0 R15: 00007fda94699fa0
 </TASK>
Modules linked in:
---[ end trace 18f094f70500b4ad ]---
RIP: 0010:__pv_queued_spin_lock_slowpath+0x290/0x9b0 kernel/locking/qspinlock.c:471
Code: c8 48 c1 e8 03 42 80 3c 28 00 74 14 48 89 4c 24 20 48 8b 7c 24 20 e8 2f 4b 59 00 48 8b 4c 24 20 4c 03 39 4c 89 f8 48 c1 e8 03 <42> 80 3c 28 00 4d 89 fd 4c 8b 7c 24 28 74 08 4c 89 ef e8 a9 4b 59
RSP: 0018:ffffc90001daf260 EFLAGS: 00010002
RAX: 00000000001ff507 RBX: ffff88810006c000 RCX: ffffffff85ea2878
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 00000000ffffffff
RBP: ffffc90001daf350 R08: 0000000000000003 R09: 0000000000000004
R10: dffffc0000000000 R11: fffffbfff0e1904c R12: 1ffff1103ee07151
R13: dffffc0000000000 R14: 1ffff1102000d800 R15: 0000000000ffa838
FS:  000055556bb45500(0000) GS:ffff8881f7000000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000200000004002 CR3: 000000012d4f1000 CR4: 00000000003506b0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
----------------
Code disassembly (best guess):
   0:	c8 48 c1 e8          	enter  $0xc148,$0xe8
   4:	03 42 80             	add    -0x80(%rdx),%eax
   7:	3c 28                	cmp    $0x28,%al
   9:	00 74 14 48          	add    %dh,0x48(%rsp,%rdx,1)
   d:	89 4c 24 20          	mov    %ecx,0x20(%rsp)
  11:	48 8b 7c 24 20       	mov    0x20(%rsp),%rdi
  16:	e8 2f 4b 59 00       	call   0x594b4a
  1b:	48 8b 4c 24 20       	mov    0x20(%rsp),%rcx
  20:	4c 03 39             	add    (%rcx),%r15
  23:	4c 89 f8             	mov    %r15,%rax
  26:	48 c1 e8 03          	shr    $0x3,%rax
* 2a:	42 80 3c 28 00       	cmpb   $0x0,(%rax,%r13,1) <-- trapping instruction
  2f:	4d 89 fd             	mov    %r15,%r13
  32:	4c 8b 7c 24 28       	mov    0x28(%rsp),%r15
  37:	74 08                	je     0x41
  39:	4c 89 ef             	mov    %r13,%rdi
  3c:	e8                   	.byte 0xe8
  3d:	a9                   	.byte 0xa9
  3e:	4b 59                	rex.WXB pop %r9

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/10/14 04:25 android13-5.15-lts 5ca734335a87 7321cd29 .config console log report syz / log [disk image] [vmlinux] [kernel image] ci2-android-5-15 UBSAN: array-index-out-of-bounds in __unfreeze_partials
* Struck through repros no longer work on HEAD.