[PATCH 6.12 529/567] usbnet: Fix using smp_processor_id() in preemptible code warnings

Greg Kroah-Hartman
2026-01-06T17:45:22Z

From: Zqiang <qiang.zhang@linux.dev>

[ Upstream commit 327cd4b68b4398b6c24f10eb2b2533ffbfc10185 ]

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@kernel.org>
Signed-off-by: Zqiang <qiang.zhang@linux.dev>
Link: https://patch.msgid.link/20251011070518.7095-1-qiang.zhang@linux.dev
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
[Harshit: Resolved conflicts due to missing commit: 2c04d279e857 ("net:
usb: Convert tasklet API to new bottom half workqueue mechanism") in
6.12.y]
Signed-off-by: Harshit Mogalapalli <harshit.m.mogalapalli@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/net/usb/usbnet.c | 2 ++
1 file changed, 2 insertions(+)

--- a/drivers/net/usb/usbnet.c
+++ b/drivers/net/usb/usbnet.c
@@ -702,6 +702,7 @@ void usbnet_resume_rx(struct usbnet *dev
struct sk_buff *skb;
int num = 0;

+ local_bh_disable();
clear_bit(EVENT_RX_PAUSED, &dev->flags);

while ((skb = skb_dequeue(&dev->rxq_pause)) != NULL) {
@@ -710,6 +711,7 @@ void usbnet_resume_rx(struct usbnet *dev
}

tasklet_schedule(&dev->bh);
+ local_bh_enable();

netif_dbg(dev, rx_status, dev->net,
"paused rx queue disabled, %d skbs requeued\n", num);