linux-kernel - Re: [PATCH v6.12] usbnet: Fix using smp_processor

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Message-ID: <2026010838-epidural-reflex-d9e7@gregkh>
Date: Thu, 8 Jan 2026 11:08:53 +0100
From: Greg KH <gregkh@...uxfoundation.org>
To: Rahul Sharma <black.hawk@....com>
Cc: stable@...r.kernel.org, linux-kernel@...r.kernel.org,
	Zqiang <qiang.zhang@...ux.dev>, Jakub Kicinski <kuba@...nel.org>,
	Paolo Abeni <pabeni@...hat.com>
Subject: Re: [PATCH v6.12] usbnet: Fix using smp_processor_id() in
 preemptible code warnings

On Wed, Jan 07, 2026 at 04:18:55PM +0800, Rahul Sharma wrote:
> From: Zqiang <qiang.zhang@...ux.dev>
> 
> Syzbot reported the following warning:
> 
> BUG: using smp_processor_id() in preemptible [00000000] code: dhcpcd/2879
> caller is usbnet_skb_return+0x74/0x490 drivers/net/usb/usbnet.c:331
> CPU: 1 UID: 0 PID: 2879 Comm: dhcpcd Not tainted 6.15.0-rc4-syzkaller-00098-g615dca38c2ea #0 PREEMPT(voluntary)
> Call Trace:
>  <TASK>
>  __dump_stack lib/dump_stack.c:94 [inline]
>  dump_stack_lvl+0x16c/0x1f0 lib/dump_stack.c:120
>  check_preemption_disabled+0xd0/0xe0 lib/smp_processor_id.c:49
>  usbnet_skb_return+0x74/0x490 drivers/net/usb/usbnet.c:331
>  usbnet_resume_rx+0x4b/0x170 drivers/net/usb/usbnet.c:708
>  usbnet_change_mtu+0x1be/0x220 drivers/net/usb/usbnet.c:417
>  __dev_set_mtu net/core/dev.c:9443 [inline]
>  netif_set_mtu_ext+0x369/0x5c0 net/core/dev.c:9496
>  netif_set_mtu+0xb0/0x160 net/core/dev.c:9520
>  dev_set_mtu+0xae/0x170 net/core/dev_api.c:247
>  dev_ifsioc+0xa31/0x18d0 net/core/dev_ioctl.c:572
>  dev_ioctl+0x223/0x10e0 net/core/dev_ioctl.c:821
>  sock_do_ioctl+0x19d/0x280 net/socket.c:1204
>  sock_ioctl+0x42f/0x6a0 net/socket.c:1311
>  vfs_ioctl fs/ioctl.c:51 [inline]
>  __do_sys_ioctl fs/ioctl.c:906 [inline]
>  __se_sys_ioctl fs/ioctl.c:892 [inline]
>  __x64_sys_ioctl+0x190/0x200 fs/ioctl.c:892
>  do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
>  do_syscall_64+0xcd/0x260 arch/x86/entry/syscall_64.c:94
>  entry_SYSCALL_64_after_hwframe+0x77/0x7f
> 
> For historical and portability reasons, the netif_rx() is usually
> run in the softirq or interrupt context, this commit therefore add
> local_bh_disable/enable() protection in the usbnet_resume_rx().
> 
> Fixes: 43daa96b166c ("usbnet: Stop RX Q on MTU change")
> Link: https://syzkaller.appspot.com/bug?id=81f55dfa587ee544baaaa5a359a060512228c1e1
> Suggested-by: Jakub Kicinski <kuba@...nel.org>
> Signed-off-by: Zqiang <qiang.zhang@...ux.dev>
> Link: https://patch.msgid.link/20251011070518.7095-1-qiang.zhang@linux.dev
> Signed-off-by: Paolo Abeni <pabeni@...hat.com>
> [ The context change is due to the commit 2c04d279e857
> ("net: usb: Convert tasklet API to new bottom half workqueue mechanism")
> in v6.17 which is irrelevant to the logic of this patch.]
> Signed-off-by: Rahul Sharma <black.hawk@....com>
> ---
>  drivers/net/usb/usbnet.c | 2 ++
>  1 file changed, 2 insertions(+)

What is the git id of this commit in Linus's tree?

thanks,

greg k-h