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Message-Id: <20250930084636.5835-1-qiang.zhang@linux.dev>
Date: Tue, 30 Sep 2025 16:46:36 +0800
From: Zqiang <qiang.zhang@...ux.dev>
To: kuba@...nel.org,
horms@...nel.org,
davem@...emloft.net,
pabeni@...hat.com
Cc: qiang.zhang@...ux.dev,
netdev@...r.kernel.org
Subject: [PATCH] usbnet: Fix using smp_processor_id() in preemptible code warnings
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
The usbnet_skb_return() can be invoked in preemptible task-context,
this commit therefore use get_cpu_ptr/put_cpu_ptr() instead of
this_cpu_ptr() to get stats64 pointer.
Fixes: 43daa96b166c ("usbnet: Stop RX Q on MTU change")
Link: https://lore.kernel.org/all/681607f0.a70a0220.254cdc.001a.GAE@google.com/T/
Signed-off-by: Zqiang <qiang.zhang@...ux.dev>
---
drivers/net/usb/usbnet.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/drivers/net/usb/usbnet.c b/drivers/net/usb/usbnet.c
index 511c4154cf74..89f79a0bdc43 100644
--- a/drivers/net/usb/usbnet.c
+++ b/drivers/net/usb/usbnet.c
@@ -328,7 +328,7 @@ static void __usbnet_status_stop_force(struct usbnet *dev)
*/
void usbnet_skb_return (struct usbnet *dev, struct sk_buff *skb)
{
- struct pcpu_sw_netstats *stats64 = this_cpu_ptr(dev->net->tstats);
+ struct pcpu_sw_netstats *stats64;
unsigned long flags;
int status;
@@ -341,10 +341,12 @@ void usbnet_skb_return (struct usbnet *dev, struct sk_buff *skb)
if (skb->protocol == 0)
skb->protocol = eth_type_trans (skb, dev->net);
+ stats64 = get_cpu_ptr(dev->net->tstats);
flags = u64_stats_update_begin_irqsave(&stats64->syncp);
u64_stats_inc(&stats64->rx_packets);
u64_stats_add(&stats64->rx_bytes, skb->len);
u64_stats_update_end_irqrestore(&stats64->syncp, flags);
+ put_cpu_ptr(stats64);
netif_dbg(dev, rx_status, dev->net, "< rx, len %zu, type 0x%x\n",
skb->len + sizeof (struct ethhdr), skb->protocol);
--
2.17.1
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