[PATCH net-next v3] net:tun: limit printing rate when illegal packet received by tun dev

[Lei Chen]

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>
Suggested-by: Paolo Abeni <pabeni@xxxxxxxxxx>
Acked-by: Jason Wang <jasowang@xxxxxxxxxx>

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));
+				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