6.6-stable review patch. If anyone has any objections, please let me know.
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From: Liu Jian liujian56@huawei.com
[ 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@huawei.com Link: https://patch.msgid.link/20250116143053.4146855-1-liujian56@huawei.com Signed-off-by: Jakub Kicinski kuba@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- 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",