[v5.15] Internal error in lock_pi_update_atomic

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: c79648372d02 Linux 5.15.189
git tree: linux-5.15.y
console output: https://syzkaller.appspot.com/x/log.txt?x=156541a2580000
kernel config: https://syzkaller.appspot.com/x/.config?x=9e47345638b85bd0
dashboard link: https://syzkaller.appspot.com/bug?extid=2f2f4989147b4de026fe
compiler: Debian clang version 20.1.7 (++20250616065708+6146a88f6049-1~exp1~20250616065826.132), Debian LLD 20.1.7
userspace arch: arm64

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/7ab49562317a/disk-c7964837.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/e847ec1e38d3/vmlinux-c7964837.xz
kernel image: https://storage.googleapis.com/syzbot-assets/263158c6371c/Image-c7964837.gz.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+2f2f49...@syzkaller.appspotmail.com

Internal error: Oops - BTI: 0000000036000001 [#1] PREEMPT SMP
Modules linked in:
CPU: 0 PID: 4179 Comm: syz.4.12 Not tainted 5.15.189-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/30/2025
pstate: 42000405 (nZcv daif -PAN -UAO +TCO -DIT -SSBS BTYPE=jc)
pc : futex_atomic_cmpxchg_inatomic arch/arm64/include/asm/futex.h:123 [inline]
pc : cmpxchg_futex_value_locked kernel/futex/core.c:779 [inline]
pc : lock_pi_update_atomic+0x158/0x254 kernel/futex/core.c:1382
lr : __uaccess_mask_ptr arch/arm64/include/asm/uaccess.h:244 [inline]
lr : futex_atomic_cmpxchg_inatomic arch/arm64/include/asm/futex.h:97 [inline]
lr : cmpxchg_futex_value_locked kernel/futex/core.c:779 [inline]
lr : lock_pi_update_atomic+0x108/0x254 kernel/futex/core.c:1382
sp : ffff80001fea74e0
x29: ffff80001fea74e0 x28: ffff0000c2de51c0 x27: 0000000000400040
x26: 0000000000000000 x25: dfff800000000000 x24: 1fffe000185bcce1
x23: 0000000000000001 x22: 00000000fffffff2 x21: 0000000000000008
x20: ffff0000c2de6708 x19: 0000000000000000 x18: 0000000000000000
x17: ffff80000805b008 x16: ffff8000083ca6a8 x15: ffff80000805b444
x14: ffff8000083c4470 x13: 1ffff0000282e06b x12: 0000000000000000
x11: 0000000020000040 x10: 00000000fffffff2 x9 : 0000000000000080
x8 : 00000000fffffff5 x7 : ffff80000820263c x6 : 0000000000000000
x5 : 0000000000000000 x4 : 0000000000000000 x3 : 0000000000000002
x2 : 0000000000000008 x1 : 0000000000000001 x0 : 0000000000000000
Call trace:
futex_atomic_cmpxchg_inatomic arch/arm64/include/asm/futex.h:99 [inline]
cmpxchg_futex_value_locked kernel/futex/core.c:779 [inline]
lock_pi_update_atomic+0x158/0x254 kernel/futex/core.c:1382
futex_lock_pi_atomic+0x440/0xea4 kernel/futex/core.c:1470
futex_lock_pi+0x2d0/0x860 kernel/futex/core.c:3054
do_futex+0x1664/0x257c kernel/futex/core.c:-1
__do_sys_futex kernel/futex/core.c:4059 [inline]
__se_sys_futex kernel/futex/core.c:4040 [inline]
__arm64_sys_futex+0x388/0x400 kernel/futex/core.c:4040
__invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:52
el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:142
do_el0_svc+0x58/0x14c arch/arm64/kernel/syscall.c:181
el0_svc+0x78/0x1e0 arch/arm64/kernel/entry-common.c:608
el0t_64_sync_handler+0xcc/0xe4 arch/arm64/kernel/entry-common.c:626
el0t_64_sync+0x1a0/0x1a4 arch/arm64/kernel/entry.S:584
Code: 4b0c0129 35ffff49 2a0803f6 d5033bbf (2a1f03e0)
---[ end trace 3924954a671594c1 ]---
----------------
Code disassembly (best guess):
0: 4b0c0129 sub w9, w9, w12
4: 35ffff49 cbnz w9, 0xffffffffffffffec
8: 2a0803f6 mov w22, w8
c: d5033bbf dmb ish
* 10: 2a1f03e0 mov w0, wzr <-- trapping instruction


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[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.