[PATCH] 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.

Rate limit 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
--- <NMI exception stack> ---
 #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

Signed-off-by: Lei Chen <lei.chen@xxxxxxxxxx>
---
 drivers/net/tun.c | 19 +++++++++++--------
 1 file changed, 11 insertions(+), 8 deletions(-)

diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index 0b3f21cba552..34c6b043764d 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -2087,6 +2087,7 @@ static ssize_t tun_put_user(struct tun_struct *tun,
 			    struct sk_buff *skb,
 			    struct iov_iter *iter)
 {
+	static DEFINE_RATELIMIT_STATE(ratelimit, 60 * HZ, 5);
 	struct tun_pi pi = { 0, skb->protocol };
 	ssize_t total;
 	int vlan_offset = 0;
@@ -2125,14 +2126,16 @@ 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 (__ratelimit(&ratelimit)) {
+				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);
+			}
 			WARN_ON_ONCE(1);
 			return -EINVAL;
 		}
-- 
2.44.0