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

[Kuniyuki Iwashima]

On Sun, 01 Nov 2026 14:12:03 +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).
> 
> Reject them at write time. message_burst can simply use
> proc_dointvec_minmax with extra1 = 0. proc_dointvec_jiffies has no
> minmax variant, so add proc_dointvec_jiffies_minmax(), mirroring
> proc_dointvec_ms_jiffies_minmax(), and use it for message_cost with
> extra1 = 0. Note that like the ms variant, extra1/extra2 are compared
> against the converted jiffies value.
> 
> Fixes: a940d145cc38 ("ratelimit: Warn if ->interval or ->burst are negative")
> Cc: stable@xxxxxxxxxxxxxxx
> Suggested-by: Joel Granados <joel.granados@xxxxxxxxxx>
> Reviewed-by: Fernando Fernandez Mancera <fmancera@xxxxxxx>
> Signed-off-by: Jiayuan Chen <jiayuan.chen@xxxxxxxxx>

Reviewed-by: Kuniyuki Iwashima <kuniyu@xxxxxxxxxx>