Re: [PATCH net v3 5/5] net: restrict message_cost and message_burst to non-negative values

[Jiayuan Chen]

On 11/2/26 9:55 AM, Hangbin Liu wrote:
> Hi Jiayuan,
> On Sun, Nov 01, 2026 at 02:12:03PM +0800, Jiayuan Chen wrote:
>> net.core.message_cost and net.core.message_burst feed the interval and
>> burst of net_ratelimit_state, but neither rejects negative values:
>> message_burst uses plain proc_dointvec, and message_cost uses
>> proc_dointvec_jiffies, which happily stores -1 second as -HZ jiffies.
>>
>> Since commit a940d145cc38 ("ratelimit: Warn if ->interval or ->burst are
>> negative"), ___ratelimit() splats on such values, so the next
>> net_ratelimit() caller warns, e.g. a martian source log:
>>
>>   Negative interval (-250) or burst (10): Uninitialized ratelimit_state structure?
>>   WARNING: lib/ratelimit.c:43 at ___ratelimit+0x56e/0x960, CPU#1: ping/3218
>>   RIP: 0010:___ratelimit+0x578/0x960
>>   Call Trace:
>>    <IRQ>
>>    net_ratelimit+0x1c/0x30
>>    ip_handle_martian_source+0x1bb/0x340
>>    ip_route_input_slow+0x1057/0x3650
>>    ip_route_input_noref+0x104/0x260
>>    arp_process+0x109b/0x2510
>>    arp_rcv+0x381/0x460
>>    __netif_receive_skb_one_core+0x173/0x1c0
>>    __netif_receive_skb+0x21/0x150
>>    process_backlog+0x37e/0x1200
>>    __napi_poll.constprop.0+0xa5/0x5e0
>>    net_rx_action+0x4c0/0xf70
>>    handle_softirqs+0x204/0x9b0
>>    __do_softirq+0x10/0x18
>>    do_softirq.part.0+0x49/0xd0
>>    </IRQ>
>>
>> Negative values never meant anything here: 0 already expresses both
>> "no limit" (interval) and "suppress everything" (burst).
> Will this limit breaks the UAPI on old kernels that supports negative values?

All commits in this series restrict config values, and every one of them
changes the old behavior to some degree; the question is whether the

change is reasonable.


For this one, negative values never did anything that 0 doesn't, and
since a940d145cc38 setting one already triggers the WARN_ONCE().


> As the comment in ___ratelimit() says:
>
>         /*
>          * Zero interval says never limit, otherwise, non-positive burst
>          * says always limit.
>          */
>
> If all others agree to set the limit in this patch. I think the comment


The comment and the WARN_ONCE() are about ratelimit_state in general, not
net only. There are still other ways to set a negative value,
printk_ratelimit for example, so updating them is not this net patch's
job.

> and the WARN_ONCE() , and the admin-guide/sysctl/net.rst all need to be updated.



net.rst never documented a range or even the unit for these two, which is
why I didn't touch it. No strong preference though.

> Thanks
> Hangbin