Re: Kernel WARNING in Xenomai3 with RTnet

[Hannes Diethelm <hannes.diethelm@gmail.com>]

Am 09.04.26 um 08:46 schrieb Jan Kiszka:
> On 08.04.26 22:53, Hannes Diethelm wrote:
>> Configuration:
>>
>> Debian Trixie
>> xenomai3:master
>> linux-dovetail:v6.12.67-dovetail1
>>
>> I have the following warning as soon as I enable the network interface:
>> Apr 08 01:52:12 trixie-box kernel: ------------[ cut here ]------------
>> Apr 08 01:52:12 trixie-box kernel: memcpy: detected field-spanning write
>> (size 80) of single field "call->priv_data" at drivers/xenomai/net/
>> stack/rtnet_rtpc.c:93 (size 0)
>> Apr 08 01:52:12 trixie-box kernel: WARNING: CPU: 13 PID: 2480 at
>> drivers/xenomai/net/stack/rtnet_rtpc.c:93
>> rtnet_rtpc_dispatch_call+0x2df/0x3d0 [rtnet]
>> Apr 08 01:52:12 trixie-box kernel: Modules linked in: rtudp rtipv4
>> rt_loopback joydev uinput qrtr rfkill binfmt_misc intel_rapl_msr
>> intel_rapl_common ccp kvm snd_hda_codec_generic snd_hda_intel ir>
>> Apr 08 01:52:12 trixie-box kernel: CPU: 13 UID: 0 PID: 2480 Comm: rtping
>> Not tainted 6.12.67-xenomai3-73ad3b #3
>> Apr 08 01:52:12 trixie-box kernel: Hardware name: QEMU Standard PC (Q35
>> + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
>> Apr 08 01:52:12 trixie-box kernel: IRQ stage: Linux
>> Apr 08 01:52:12 trixie-box kernel: RIP:
>> 0010:rtnet_rtpc_dispatch_call+0x2df/0x3d0 [rtnet]
>> Apr 08 01:52:12 trixie-box kernel: Code: 26 50 00 00 00 0f 85 d1 fd ff
>> ff 31 c9 48 c7 c2 00 13 94 c0 4c 89 ee 48 c7 c7 48 13 94 c0 c6 05 06 50
>> 00 00 01 e8 51 d6 97 eb <0f> 0b e9 ab fd ff ff 84 d2 >
>> Apr 08 01:52:12 trixie-box kernel: RSP: 0018:ffffcdff82ebbd68 EFLAGS:
>> 00010286
>> Apr 08 01:52:12 trixie-box kernel: RAX: 0000000000000000 RBX:
>> ffff8988585012c0 RCX: 0000000000000027
>> Apr 08 01:52:12 trixie-box kernel: RDX: ffff898b6fca0948 RSI:
>> 0000000000000001 RDI: ffff898b6fca0940
>> Apr 08 01:52:12 trixie-box kernel: RBP: 00000000000001f4 R08:
>> 0000000000000000 R09: ffffcdff82ebbb28
>> Apr 08 01:52:12 trixie-box kernel: R10: ffffffffadeb9ee8 R11:
>> 0000000000000003 R12: 0000000000000000
>> Apr 08 01:52:12 trixie-box kernel: R13: 0000000000000050 R14:
>> ffffffffc0cff5b0 R15: ffffffffc0cff6e0
>> Apr 08 01:52:12 trixie-box kernel: FS:  00007f1499d11740(0000)
>> GS:ffff898b6fc80000(0000) knlGS:0000000000000000
>> Apr 08 01:52:12 trixie-box kernel: CS:  0010 DS: 0000 ES: 0000 CR0:
>> 0000000080050033
>> Apr 08 01:52:12 trixie-box kernel: CR2: 00007ffe3de7dff8 CR3:
>> 000000014d74e000 CR4: 0000000000750ef0
>> Apr 08 01:52:12 trixie-box kernel: PKRU: 55555554
>> Apr 08 01:52:12 trixie-box kernel: Call Trace:
>> Apr 08 01:52:12 trixie-box kernel:  <TASK>
>> Apr 08 01:52:12 trixie-box kernel:  ipv4_ioctl+0x16b/0x230 [rtipv4]
>> Apr 08 01:52:12 trixie-box kernel:  rtnet_ioctl+0x164/0x190 [rtnet]
>> Apr 08 01:52:12 trixie-box kernel:  ? __count_memcg_events+0x67/0x100
>> Apr 08 01:52:12 trixie-box kernel:  __x64_sys_ioctl+0x91/0xd0
>> Apr 08 01:52:12 trixie-box kernel:  do_syscall_64+0xc0/0x230
>> Apr 08 01:52:12 trixie-box kernel: entry_SYSCALL_64_after_hwframe+0x76/0x7e
>> Apr 08 01:52:12 trixie-box kernel: RIP: 0033:0x7f1499e2091b
>> Apr 08 01:52:12 trixie-box kernel: Code: 00 48 89 44 24 18 31 c0 48 8d
>> 44 24 60 c7 04 24 10 00 00 00 48 89 44 24 08 48 8d 44 24 20 48 89 44 24
>> 10 b8 10 00 00 00 0f 05 <89> c2 3d 00 f0 ff ff 77 1c >
>> Apr 08 01:52:12 trixie-box kernel: RSP: 002b:00007ffe3de7e9f0 EFLAGS:
>> 00000246 ORIG_RAX: 0000000000000010
>> Apr 08 01:52:12 trixie-box kernel: RAX: ffffffffffffffda RBX:
>> 00007f1499d11740 RCX: 00007f1499e2091b
>> Apr 08 01:52:12 trixie-box kernel: RDX: 000055c8e00d60e0 RSI:
>> 00000000c0500285 RDI: 0000000000000003
>> Apr 08 01:52:12 trixie-box kernel: RBP: 0000000000000002 R08:
>> 0000000000000000 R09: 0000000000000000
>> Apr 08 01:52:12 trixie-box kernel: R10: 0000000000000003 R11:
>> 0000000000000246 R12: 00007ffe3de7f818
>> Apr 08 01:52:12 trixie-box kernel: R13: 0000000000000002 R14:
>> 00007f1499f60000 R15: 000055c8e00d5dd8
>> Apr 08 01:52:12 trixie-box kernel:  </TASK>
>> Apr 08 01:52:12 trixie-box kernel: ---[ end trace 0000000000000000 ]---
>>
>> This can be fixed with the following patch. However, I am not sure if
>> it's the right way to do it.
>> diff --git a/kernel/drivers/net/stack/rtnet_rtpc.c b/kernel/drivers/net/
>> stack/rtnet_rtpc.c
>> index cd5f0546d..caed27269 100644
>> --- a/kernel/drivers/net/stack/rtnet_rtpc.c
>> +++ b/kernel/drivers/net/stack/rtnet_rtpc.c
>> @@ -90,7 +90,7 @@ int rtnet_rtpc_dispatch_call(rtpc_proc proc, unsigned
>> int timeout,
>>       if (call == NULL)
>>           return -ENOMEM;
>>
>> -    memcpy(call->priv_data, priv_data, priv_data_size);
>> +    unsafe_memcpy(call->priv_data, priv_data, priv_data_size, /
>> *embedded variable length data*/);
>>
> 
> Yeah, good catch - the kernel and the toolchains improved their
> diagnosis features a lot since this was written more than 20 years ago.
> I bet we have a few more of those variable length fields in RTnet data
> structures. Those should be converted to flexible array members, see
> also
> https://www.kernel.org/doc/html/latest/process/deprecated.html#zero-length-and-one-element-arrays.
> Happy to review patches!
> 
> Jan
Thanks for the hint. So I think this is all that's needed, i tested it and with this change. I also have no
warnings any more.

diff --git a/kernel/drivers/net/stack/include/rtnet_rtpc.h b/kernel/drivers/net/stack/include/rtnet_rtpc.h
index 01d7ab152..f4ad47306 100644
--- a/kernel/drivers/net/stack/include/rtnet_rtpc.h
+++ b/kernel/drivers/net/stack/include/rtnet_rtpc.h
@@ -43,7 +43,7 @@ struct rt_proc_call {
         atomic_t ref_count;
         wait_queue_head_t call_wq;
         rtpc_cleanup_proc cleanup_handler;
-       char priv_data[0] __attribute__((aligned(8)));
+       char priv_data[] __attribute__((aligned(8)));
  };
  
  #define CALL_PENDING 1000 /* result value for blocked calls */

So you mean I should submit a patch? So that means using git format-patch and send it to the mailing list?
I can try that but I can't guarantee I won't mess it up. But I allready managed to setup my e-mail client to not
mess up the messages.

I have another patch and a bug report in the pipeline but one at a time.

Just some background: I am working on integrating Xenomai3/4 into LinuxCNC. It is just a hobby and I am not an official
maintainer. However, I am using Linux since i switched over from Windows 3.11 and I am quite experienced in C/C++ from
my day job and also personal projects. But the last time I was using mailing lists was like 20 years ago.

Hannes
> 
>>       call->processed = 0;
>>       call->proc = proc;
>>
>>
>