linux-kernel - Unpatched return thunk in use. This should not happen!

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Message-ID: <ecc308bc-3520-4a65-9f17-2109c4f5d280@gmail.com>
Date: Tue, 25 Mar 2025 21:55:07 +0100
From: Heiner Kallweit <hkallweit1@...il.com>
To: Andy Lutomirski <luto@...nel.org>, Brian Gerst <brgerst@...il.com>,
 Ingo Molnar <mingo@...nel.org>
Cc: Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Unpatched return thunk in use. This should not happen!

I get the following with today's linux-next, did not occur on linux-next from March 12th.
System is a N100-based mini-pc.
Over the last days I see several changes to the x86/entry code, therefore think it might
be related. If more info should be needed, please let me know.

Unpatched return thunk in use. This should not happen!
WARNING: CPU: 0 PID: 1 at arch/x86/kernel/cpu/bugs.c:3107 __warn_thunk+0x26/0x30
Modules linked in:
CPU: 0 UID: 0 PID: 1 Comm: swapper/0 Not tainted 6.14.0-next-20250325+ #2 PREEMPT(undef)
Hardware name: Default string Default string/Default string, BIOS ADLN.M6.SODIMM.ZB.CY.015 08/08/2023
RIP: 0010:__warn_thunk+0x26/0x30
Code: 90 90 90 90 55 48 89 e5 80 3d e3 18 3a 01 00 74 06 5d c3 cc cc cc cc 48 c7 c7 08 cd 56 ad c6 05 cd 18 3a 01 01 e8 4a e7 03 00 <0f>>
RSP: 0000:ffffb5e80006fe18 EFLAGS: 00010286
RAX: 0000000000000000 RBX: ffffffffacd76060 RCX: 0000000000000000
RDX: 0000000000000002 RSI: 0000000000000003 RDI: 00000000ffffffff
RBP: ffffb5e80006fe18 R08: 0000000000000000 R09: ffffffffad94ece8
R10: ffffffffad91eca8 R11: 0000000000000003 R12: 0000000000000000
R13: 0000000000000044 R14: ffffffffadb7e794 R15: 0000000000000000
FS:  0000000000000000(0000) GS:ffff924949d68000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffff9248ffbff000 CR3: 0000000021050001 CR4: 0000000000770ef0
PKRU: 55555554
Call Trace:
 <TASK>
 ? show_regs.part.0+0x1d/0x30
 ? show_regs.cold+0x8/0xd
 ? __warn_thunk+0x26/0x30
 ? __warn.cold+0xc2/0x15e
 ? __warn_thunk+0x26/0x30
 ? report_bug+0xe3/0x170
 ? console_unlock+0x7d/0x110
 ? __warn_thunk+0x26/0x30
 ? __warn_thunk+0x28/0x30
 ? handle_bug+0x116/0x170
 ? exc_invalid_op+0x18/0x70
 ? asm_exc_invalid_op+0x1b/0x20
 ? iommu_dma_ranges_sort+0x30/0x30
 ? __warn_thunk+0x26/0x30
 ? __warn_thunk+0x26/0x30
 warn_thunk_thunk+0x16/0x30
 ? __cpuhp_setup_state_cpuslocked+0x65/0x310
 do_one_initcall+0x54/0x390
 ? debug_smp_processor_id+0x17/0x20
 ? rcu_is_watching+0x11/0x50
 kernel_init_freeable+0x268/0x2b0
 ? __pfx_kernel_init+0x10/0x10
 kernel_init+0x15/0x120
 ret_from_fork+0x35/0x60
 ? __pfx_kernel_init+0x10/0x10
 ret_from_fork_asm+0x1a/0x30
RIP: 1f0f:0x0
Code: Unable to access opcode bytes at 0xffffffffffffffd6.
RSP: 0000:0000000000000000 EFLAGS: 841f0f2e66 ORIG_RAX: 1f0f2e6600000000
RAX: 0000000000000000 RBX: 1f0f2e6600000000 RCX: 2e66000000000084
RDX: 0000000000841f0f RSI: 000000841f0f2e66 RDI: 00841f0f2e660000
RBP: 00841f0f2e660000 R08: 00841f0f2e660000 R09: 000000841f0f2e66
R10: 0000000000841f0f R11: 2e66000000000084 R12: 000000841f0f2e66
R13: 0000000000841f0f R14: 2e66000000000084 R15: 1f0f2e6600000000
 </TASK>
irq event stamp: 5001
hardirqs last  enabled at (5009): [<ffffffffac76cdae>] __up_console_sem+0x5e/0x80
hardirqs last disabled at (5016): [<ffffffffac76cd93>] __up_console_sem+0x43/0x80
softirqs last  enabled at (4592): [<ffffffffac6d7f4c>] __irq_exit_rcu+0xbc/0x120
softirqs last disabled at (4587): [<ffffffffac6d7f4c>] __irq_exit_rcu+0xbc/0x120