Re: [PATCH net-next v4] tun: limit printing rate when illegal packet received by tun dev

[Willem de Bruijn]

Lei Chen wrote:
> vhost_worker will call tun call backs to receive packets. If too many
> illegal packets arrives, tun_do_read will keep dumping packet contents.
> When console is enabled, it will costs much more cpu time to dump
> packet and soft lockup will be detected.
> 
> net_ratelimit mechanism can be used to limit the dumping rate.
> 
> PID: 33036    TASK: ffff949da6f20000  CPU: 23   COMMAND: "vhost-32980"
>  #0 [fffffe00003fce50] crash_nmi_callback at ffffffff89249253
>  #1 [fffffe00003fce58] nmi_handle at ffffffff89225fa3
>  #2 [fffffe00003fceb0] default_do_nmi at ffffffff8922642e
>  #3 [fffffe00003fced0] do_nmi at ffffffff8922660d
>  #4 [fffffe00003fcef0] end_repeat_nmi at ffffffff89c01663
>     [exception RIP: io_serial_in+20]
>     RIP: ffffffff89792594  RSP: ffffa655314979e8  RFLAGS: 00000002
>     RAX: ffffffff89792500  RBX: ffffffff8af428a0  RCX: 0000000000000000
>     RDX: 00000000000003fd  RSI: 0000000000000005  RDI: ffffffff8af428a0
>     RBP: 0000000000002710   R8: 0000000000000004   R9: 000000000000000f
>     R10: 0000000000000000  R11: ffffffff8acbf64f  R12: 0000000000000020
>     R13: ffffffff8acbf698  R14: 0000000000000058  R15: 0000000000000000
>     ORIG_RAX: ffffffffffffffff  CS: 0010  SS: 0018
>  #5 [ffffa655314979e8] io_serial_in at ffffffff89792594
>  #6 [ffffa655314979e8] wait_for_xmitr at ffffffff89793470
>  #7 [ffffa65531497a08] serial8250_console_putchar at ffffffff897934f6
>  #8 [ffffa65531497a20] uart_console_write at ffffffff8978b605
>  #9 [ffffa65531497a48] serial8250_console_write at ffffffff89796558
>  #10 [ffffa65531497ac8] console_unlock at ffffffff89316124
>  #11 [ffffa65531497b10] vprintk_emit at ffffffff89317c07
>  #12 [ffffa65531497b68] printk at ffffffff89318306
>  #13 [ffffa65531497bc8] print_hex_dump at ffffffff89650765
>  #14 [ffffa65531497ca8] tun_do_read at ffffffffc0b06c27 [tun]
>  #15 [ffffa65531497d38] tun_recvmsg at ffffffffc0b06e34 [tun]
>  #16 [ffffa65531497d68] handle_rx at ffffffffc0c5d682 [vhost_net]
>  #17 [ffffa65531497ed0] vhost_worker at ffffffffc0c644dc [vhost]
>  #18 [ffffa65531497f10] kthread at ffffffff892d2e72
>  #19 [ffffa65531497f50] ret_from_fork at ffffffff89c0022f
> 
> Fixes: ef3db4a59542 ("tun: avoid BUG, dump packet on GSO errors")
> Signed-off-by: Lei Chen <lei.chen@xxxxxxxxxx>
> Reviewed-by: Willem de Bruijn <willemb@xxxxxxxxxx>
> Acked-by: Jason Wang <jasowang@xxxxxxxxxx>
> ---
> Changes from v3:
> https://lore.kernel.org/all/20240412065841.2148691-1-lei.chen@xxxxxxxxxx/
>  1. Change patch target from net tun to tun.
>  2. Move change log below the seperator "---".
>  3. Remove escaped parentheses in the Fixes string.
> 
> Changes from v2:
> https://lore.kernel.org/netdev/20240410042245.2044516-1-lei.chen@xxxxxxxxxx/
>  1. Add net-dev to patch subject-prefix.
>  2. Add fix tag.
> 
> Changes from v1:
> https://lore.kernel.org/all/20240409062407.1952728-1-lei.chen@xxxxxxxxxx/
>  1. Use net_ratelimit instead of raw __ratelimit.
>  2. Use netdev_err instead of pr_err to print more info abort net dev.
>  3. Adjust git commit message to make git am happy.
>  drivers/net/tun.c | 18 ++++++++++--------
>  1 file changed, 10 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/net/tun.c b/drivers/net/tun.c
> index 0b3f21cba552..ca9b4bc89de7 100644
> --- a/drivers/net/tun.c
> +++ b/drivers/net/tun.c
> @@ -2125,14 +2125,16 @@ static ssize_t tun_put_user(struct tun_struct *tun,
>  					    tun_is_little_endian(tun), true,
>  					    vlan_hlen)) {
>  			struct skb_shared_info *sinfo = skb_shinfo(skb);
> -			pr_err("unexpected GSO type: "
> -			       "0x%x, gso_size %d, hdr_len %d\n",
> -			       sinfo->gso_type, tun16_to_cpu(tun, gso.gso_size),
> -			       tun16_to_cpu(tun, gso.hdr_len));
> -			print_hex_dump(KERN_ERR, "tun: ",
> -				       DUMP_PREFIX_NONE,
> -				       16, 1, skb->head,
> -				       min((int)tun16_to_cpu(tun, gso.hdr_len), 64), true);
> +
> +			if (net_ratelimit()) {
> +				netdev_err(tun->dev, "unexpected GSO type: 0x%x, gso_size %d, hdr_len %d\n",
> +				       sinfo->gso_type, tun16_to_cpu(tun, gso.gso_size),
> +				       tun16_to_cpu(tun, gso.hdr_len));

Indentation. checkpatch or patchwork will also show this.

> +				print_hex_dump(KERN_ERR, "tun: ",
> +					       DUMP_PREFIX_NONE,
> +					       16, 1, skb->head,
> +					       min((int)tun16_to_cpu(tun, gso.hdr_len), 64), true);
> +			}
>  			WARN_ON_ONCE(1);
>  			return -EINVAL;
>  		}
> -- 
> 2.44.0
>