[syzbot] [kernel?] Internal error in futex_cmpxchg_value_locked
From: syzbot
Date: Tue Sep 08 2026 - 18:10:43 EST
Hello,
syzbot found the following issue on:
HEAD commit: 5445d6419962 arm64: Don't read GMID_EL1 when MTE is disabled
git tree: git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci
console output: https://syzkaller.appspot.com/x/log.txt?x=16f87125580000
kernel config: https://syzkaller.appspot.com/x/.config?x=56ed23170c168d4c
dashboard link: https://syzkaller.appspot.com/bug?extid=635d160c0d4133481520
compiler: Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8
userspace arch: arm64
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=15f87125580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=107f3af9580000
Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/e8b70e3bd109/disk-5445d641.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/e5227e56ac93/vmlinux-5445d641.xz
kernel image: https://storage.googleapis.com/syzbot-assets/54905f78be59/Image-5445d641.gz.xz
IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+635d160c0d4133481520@xxxxxxxxxxxxxxxxxxxxxxxxx
Internal error: synchronous external abort: 0000000096000010 [#1] SMP
Modules linked in:
CPU: 0 UID: 0 PID: 4916 Comm: syz.0.17 Tainted: G M syzkaller #0 PREEMPT
Tainted: [M]=MACHINE_CHECK
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/07/2026
pstate: 83000005 (Nzcv daif -PAN -UAO +TCO +DIT -SSBS BTYPE=--)
pc : __llsc_futex_cmpxchg arch/arm64/include/asm/futex.h:64 [inline]
pc : __futex_cmpxchg arch/arm64/include/asm/futex.h:247 [inline]
pc : futex_atomic_cmpxchg_inatomic arch/arm64/include/asm/futex.h:295 [inline]
pc : futex_cmpxchg_value_locked+0x114/0x394 kernel/futex/futex.h:295
lr : access_ok arch/arm64/include/asm/uaccess.h:45 [inline]
lr : futex_atomic_cmpxchg_inatomic arch/arm64/include/asm/futex.h:290 [inline]
lr : futex_cmpxchg_value_locked+0xc8/0x394 kernel/futex/futex.h:295
sp : ffff80009ab17750
x29: ffff80009ab17770 x28: 1fffe000189dc765 x27: ffff0000c4ee3b2c
x26: 1fffe000189dca44 x25: dfff800000000000 x24: 0000000000000000
x23: 0000000000000000 x22: 000000008f0101ff x21: 000000000f0101ff
x20: 000ffffffffffffd x19: ffff0000c4ee5224 x18: 0000000000000000
x17: ffff8000805acb44 x16: ffff8000805ac7e0 x15: ffff8000805b05f8
x14: ffff8000805aea98 x13: 0000000000000009 x12: 0000000000000000
x11: 0000000072c79ec1 x10: 0000000000000080 x9 : 00000000fffffff5
x8 : 0000000000000000 x7 : ffff800080375350 x6 : 0000000000000000
x5 : 0000000000000000 x4 : 0000000000000000 x3 : ffff8000805b145c
x2 : 0000000000000000 x1 : ffff0000c4ee3b00 x0 : 0000000000000000
Call trace:
__llsc_futex_cmpxchg arch/arm64/include/asm/futex.h:64 [inline] (P)
__futex_cmpxchg arch/arm64/include/asm/futex.h:247 [inline] (P)
futex_atomic_cmpxchg_inatomic arch/arm64/include/asm/futex.h:295 [inline] (P)
futex_cmpxchg_value_locked+0x114/0x394 kernel/futex/futex.h:295 (P)
lock_pi_update_atomic+0x58/0xd4 kernel/futex/pi.c:549
futex_lock_pi_atomic+0x28c/0x898 kernel/futex/pi.c:666
futex_lock_pi+0x248/0x6e0 kernel/futex/pi.c:1018
do_futex+0x2f8/0x378 kernel/futex/syscalls.c:-1
__do_sys_futex kernel/futex/syscalls.c:210 [inline]
__se_sys_futex kernel/futex/syscalls.c:191 [inline]
__arm64_sys_futex+0x2e4/0x418 kernel/futex/syscalls.c:191
__invoke_syscall arch/arm64/kernel/syscall.c:35 [inline]
invoke_syscall+0x98/0x244 arch/arm64/kernel/syscall.c:49
el0_svc_common+0xec/0x23c arch/arm64/kernel/syscall.c:121
do_el0_svc+0x4c/0x5c arch/arm64/kernel/syscall.c:140
el0_svc+0x64/0x260 arch/arm64/kernel/entry-common.c:758
el0t_64_sync_handler+0x44/0x104 arch/arm64/kernel/entry-common.c:777
el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:590
Code: 2a1f03e0 12800149 d500409f f9800111 (885f7d14)
---[ end trace 0000000000000000 ]---
----------------
Code disassembly (best guess):
0: 2a1f03e0 mov w0, wzr
4: 12800149 mov w9, #0xfffffff5 // #-11
8: d500409f msr pan, #0x0
c: f9800111 prfm pstl1strm, [x8]
* 10: 885f7d14 ldxr w20, [x8] <-- trapping instruction
---
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