Error while loading dw-i3c-master: UBSAN: shift-out-of-bounds in drivers/i3c/master/dw-i3c-master.c:885:12

[Louis Sautier]

On 12/9/25 13:48, Alexandre Belloni wrote:
>
> On 09/12/2025 12:37:12+0100, Louis Sautier wrote:
>> On 12/8/25 21:58, Alexandre Belloni wrote:
>>> Hello Louis,
>>>
>>> On 02/12/2025 21:17:31+0100, Louis Sautier wrote:
>>>> Hello,
>>>>
>>>> I'm running into a bug when loading the dw-i3c-master module on kernel 6.18
>>>> on one specific server. I suspect it has to do with the large number of
>>>> CPUs on the machine (768 threads, from 2 AMD EPYC 9965 processors) but I am
>>>> not sure.
>>>>
>>>> The system is on Ubuntu 25.10 and a 6.18 kernel with https://gist.githubusercontent.com/sbraz/a6f37fafbcf9354bbe4eace9e9eb48cb/raw/115da594dc9d7ea99b06754847571e6fd76d9da5/config
>>>> (basically Ubuntu's).
>>> Just to be sure, does this also happen with v6.17?
>>>
>>> The only change is the shutdown handling so I would guess yes.
>>>
>> Hello,
>>
>> It does happen with 6.17. I initially discovered this while running Ubuntu
>> 25.10's stock kernel (6.17.0).
>>
>>> What is the behavior when you build the dw-i3c-master as a static driver?
>> I'll try CONFIG_DW_I3C_MASTER=y and report back.
>>
>> Someone also suggested (they didn't reply to the list though) that I add a
>> printk to see what the value of maxdevs is. I'll provide the log as soon as
>> I have rebuilt with:
>>
>> --- linux-6.18.orig/drivers/i3c/master/dw-i3c-master.c	2025-11-30 22:42:10.000000000 +0000
>> +++ linux-6.18/drivers/i3c/master/dw-i3c-master.c	2025-12-08 18:17:33.151567225 +0000
>> @@ -1588,6 +1588,7 @@
>>   	ret = readl(master->regs + DEVICE_ADDR_TABLE_POINTER);
>>   	master->datstartaddr = ret;
>>   	master->maxdevs = ret >> 16;
>> +	printk("maxdevs: %d\n",  master->maxdevs);
>>   	master->free_pos = GENMASK(master->maxdevs - 1, 0);
>>   	master->quirks = (unsigned long)device_get_match_data(&pdev->dev);
>>
> Yes, that was going to be my suggestion.
>
I haven't tried with the driver built-in yet. This is what the printk shows:
dw-i3c-master AMDI0015:00: probe with driver dw-i3c-master failed with 
error -110
maxdevs: 65535
dw-i3c-master AMDI0015:01: probe with driver dw-i3c-master failed with 
error -110
maxdevs: 11
------------[ cut here ]------------
UBSAN: shift-out-of-bounds in drivers/i3c/master/dw-i3c-master.c:885:12
shift exponent 64 is too large for 64-bit type 'long unsigned int'
CPU: 0 UID: 0 PID: 7363 Comm: (udev-worker) Not tainted 6.18.0 #1 
PREEMPT(voluntary)
Hardware name: Giga Computing MZ73-LM2-000/MZ73-LM2-000, BIOS R23_F43 
11/28/2025
Call Trace:
  <TASK>
  dump_stack_lvl+0x5f/0x90
  dump_stack+0x10/0x18
  ubsan_epilogue+0x9/0x39
  __ubsan_handle_shift_out_of_bounds.cold+0xdd/0x1c9
  dw_i3c_master_daa.cold+0x1a/0x90 [dw_i3c_master]
  i3c_master_do_daa+0x30/0x90 [i3c]
  i3c_master_register+0x616/0xa80 [i3c]
  dw_i3c_common_probe+0x298/0x2d0 [dw_i3c_master]
  dw_i3c_probe+0x30/0x50 [dw_i3c_master]
  platform_probe+0x42/0xc0
  ? driver_sysfs_add+0x63/0xd0
  really_probe+0xf9/0x370
  ? pm_runtime_barrier+0x56/0xa0
  __driver_probe_device+0x8b/0x160
  driver_probe_device+0x24/0xd0
  ? __pfx___driver_attach+0x10/0x10
  __driver_attach+0xef/0x220
  ? __pfx_dw_i3c_driver_init+0x10/0x10 [dw_i3c_master]
  bus_for_each_dev+0x8a/0xe0
  driver_attach+0x1e/0x30
  bus_add_driver+0x13e/0x230
  ? __pfx_dw_i3c_driver_init+0x10/0x10 [dw_i3c_master]
  driver_register+0x75/0xf0
  __platform_driver_register+0x1e/0x30
  dw_i3c_driver_init+0x1c/0xff0 [dw_i3c_master]
  do_one_initcall+0x59/0x330
  do_init_module+0x8b/0x290
  load_module+0x1f2f/0x2320
  init_module_from_file+0x9b/0x100
  ? init_module_from_file+0x9b/0x100
  idempotent_init_module+0x10e/0x300
  __x64_sys_finit_module+0x73/0xf0
  ? __secure_computing+0x84/0xe0
  x64_sys_call+0x1f04/0x2350
  do_syscall_64+0x82/0xc80
  ? vfs_read+0x179/0x3a0
  ? vfs_read+0x179/0x3a0
  ? __rseq_handle_notify_resume+0xa2/0x4e0
  ? exit_to_user_mode_loop+0xe6/0x190
  ? do_syscall_64+0x25c/0xc80
  ? irqentry_exit+0x43/0x50
  ? exc_page_fault+0x90/0x1b0
  entry_SYSCALL_64_after_hwframe+0x76/0x7e
RIP: 0033:0x70c8bf1348cd
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 90 f3 0f 1e fa 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 8b 0d 13 f5 0f 00 f7 d8 64 89 01 48
RSP: 002b:00007ffd8d0e4cf8 EFLAGS: 00000246 ORIG_RAX: 0000000000000139
RAX: ffffffffffffffda RBX: 000059c987bf15c0 RCX: 000070c8bf1348cd
RDX: 0000000000000000 RSI: 000070c8be74b336 RDI: 0000000000000065
RBP: 00007ffd8d0e4d90 R08: 0000000000000000 R09: 000059c987bc1070
R10: 0000000000000000 R11: 0000000000000246 R12: 000070c8be74b336
R13: 0000000000020000 R14: 000059c987be8cd0 R15: 000059c987bb1440
  </TASK>
---[ end trace ]---
maxdevs: 11
dw-i3c-master AMDI0015:03: probe with driver dw-i3c-master failed with 
error -110