6.6-stable review patch. If anyone has any objections, please let me know.
------------------
From: Liu Jian <liujian56@xxxxxxxxxx>
[ Upstream commit d1f9f79fa2af8e3b45cffdeef66e05833480148a ]
The following problem was encountered during stability test:
(NULL net_device): NAPI poll function process_backlog+0x0/0x530 \
returned 1, exceeding its budget of 0.
------------[ cut here ]------------
list_add double add: new=ffff88905f746f48, prev=ffff88905f746f48, \
next=ffff88905f746e40.
WARNING: CPU: 18 PID: 5462 at lib/list_debug.c:35 \
__list_add_valid_or_report+0xf3/0x130
CPU: 18 UID: 0 PID: 5462 Comm: ping Kdump: loaded Not tainted 6.13.0-rc7+
RIP: 0010:__list_add_valid_or_report+0xf3/0x130
Call Trace:
? __warn+0xcd/0x250
? __list_add_valid_or_report+0xf3/0x130
enqueue_to_backlog+0x923/0x1070
netif_rx_internal+0x92/0x2b0
__netif_rx+0x15/0x170
loopback_xmit+0x2ef/0x450
dev_hard_start_xmit+0x103/0x490
__dev_queue_xmit+0xeac/0x1950
ip_finish_output2+0x6cc/0x1620
ip_output+0x161/0x270
ip_push_pending_frames+0x155/0x1a0
raw_sendmsg+0xe13/0x1550
__sys_sendto+0x3bf/0x4e0
__x64_sys_sendto+0xdc/0x1b0
do_syscall_64+0x5b/0x170
entry_SYSCALL_64_after_hwframe+0x76/0x7e
The reproduction command is as follows:
sysctl -w net.core.dev_weight=0
ping 127.0.0.1
This is because when the napi's weight is set to 0, process_backlog() may
return 0 and clear the NAPI_STATE_SCHED bit of napi->state, causing this
napi to be re-polled in net_rx_action() until __do_softirq() times out.
Since the NAPI_STATE_SCHED bit has been cleared, napi_schedule_rps() can
be retriggered in enqueue_to_backlog(), causing this issue.
Making the napi's weight always non-zero solves this problem.
Triggering this issue requires system-wide admin (setting is
not namespaced).
Fixes: e38766054509 ("[NET]: Fix sysctl net.core.dev_weight")
Fixes: 3d48b53fb2ae ("net: dev_weight: TX/RX orthogonality")
Signed-off-by: Liu Jian <liujian56@xxxxxxxxxx>
Link: https://patch.msgid.link/20250116143053.4146855-1-liujian56@xxxxxxxxxx
Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
net/core/sysctl_net_core.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/net/core/sysctl_net_core.c b/net/core/sysctl_net_core.c
index 373b5b2231c49..0b15272dd2d35 100644
--- a/net/core/sysctl_net_core.c
+++ b/net/core/sysctl_net_core.c
@@ -297,7 +297,7 @@ static int proc_do_dev_weight(struct ctl_table *table, int write,
int ret, weight;
mutex_lock(&dev_weight_mutex);
- ret = proc_dointvec(table, write, buffer, lenp, ppos);
+ ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
if (!ret && write) {
weight = READ_ONCE(weight_p);
WRITE_ONCE(dev_rx_weight, weight * dev_weight_rx_bias);
@@ -422,6 +422,7 @@ static struct ctl_table net_core_table[] = {
.maxlen = sizeof(int),
.mode = 0644,
.proc_handler = proc_do_dev_weight,
+ .extra1 = SYSCTL_ONE,
},
{
.procname = "dev_weight_rx_bias",
@@ -429,6 +430,7 @@ static struct ctl_table net_core_table[] = {
.maxlen = sizeof(int),
.mode = 0644,
.proc_handler = proc_do_dev_weight,
+ .extra1 = SYSCTL_ONE,
},
{
.procname = "dev_weight_tx_bias",
@@ -436,6 +438,7 @@ static struct ctl_table net_core_table[] = {
.maxlen = sizeof(int),
.mode = 0644,
.proc_handler = proc_do_dev_weight,
+ .extra1 = SYSCTL_ONE,
},
{
.procname = "netdev_max_backlog",
--
2.39.5
