After commit baeababb5b85d5c4e6c917efe2a1504179438d3b
("tun: return NET_XMIT_DROP for dropped packets"),
when tun_net_xmit drop packets, it will free skb and return NET_XMIT_DROP,
netpoll_send_skb_on_dev will run into two use after free cases:
1. retry netpoll_start_xmit with freed skb;
2. queue freed skb in npinfo->txq.
hit the first case with following kernel log:
[ 117.864773] kernel BUG at mm/slub.c:306!
[ 117.864773] invalid opcode: 0000 [#1] SMP PTI
[ 117.864774] CPU: 3 PID: 2627 Comm: loop_printmsg Kdump: loaded Tainted: P
OE 5.3.0-050300rc5-generic #201908182231
[ 117.864775] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS
Ubuntu-1.8.2-1ubuntu1 04/01/2014
[ 117.864775] RIP: 0010:kmem_cache_free+0x28d/0x2b0
[ 117.864781] Call Trace:
[ 117.864781] ? tun_net_xmit+0x21c/0x460
[ 117.864781] kfree_skbmem+0x4e/0x60
[ 117.864782] kfree_skb+0x3a/0xa0
[ 117.864782] tun_net_xmit+0x21c/0x460
[ 117.864782] netpoll_start_xmit+0x11d/0x1b0
[ 117.864788] netpoll_send_skb_on_dev+0x1b8/0x200
[ 117.864789] __br_forward+0x1b9/0x1e0 [bridge]
[ 117.864789] ? skb_clone+0x53/0xd0
[ 117.864790] ? __skb_clone+0x2e/0x120
[ 117.864790] deliver_clone+0x37/0x50 [bridge]
[ 117.864790] maybe_deliver+0x89/0xc0 [bridge]
[ 117.864791] br_flood+0x6c/0x130 [bridge]
[ 117.864791] br_dev_xmit+0x315/0x3c0 [bridge]
[ 117.864792] netpoll_start_xmit+0x11d/0x1b0
[ 117.864792] netpoll_send_skb_on_dev+0x1b8/0x200
[ 117.864792] netpoll_send_udp+0x2c6/0x3e8
[ 117.864793] write_msg+0xd9/0xf0 [netconsole]
[ 117.864793] console_unlock+0x386/0x4e0
[ 117.864793] vprintk_emit+0x17e/0x280
[ 117.864794] vprintk_default+0x29/0x50
[ 117.864794] vprintk_func+0x4c/0xbc
[ 117.864794] printk+0x58/0x6f
[ 117.864795] loop_fun+0x24/0x41 [printmsg_loop]
[ 117.864795] kthread+0x104/0x140
[ 117.864795] ? 0xffffffffc05b1000
[ 117.864796] ? kthread_park+0x80/0x80
[ 117.864796] ret_from_fork+0x35/0x40
Signed-off-by: Feng Sun <loyo...@gmail.com>
Signed-off-by: Xiaojun Zhao <xiaojunzhao...@gmail.com>
---
net/core/netpoll.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/net/core/netpoll.c b/net/core/netpoll.c
index 2cf27da..b4bffe6 100644
--- a/net/core/netpoll.c
+++ b/net/core/netpoll.c
@@ -335,7 +335,7 @@ void netpoll_send_skb_on_dev(struct netpoll *np, struct
sk_buff *skb,
HARD_TX_UNLOCK(dev, txq);
- if (status == NETDEV_TX_OK)
+ if (status == NETDEV_TX_OK || status ==
NET_XMIT_DROP)
break;
}
@@ -352,7 +352,7 @@ void netpoll_send_skb_on_dev(struct netpoll *np, struct
sk_buff *skb,
}
- if (status != NETDEV_TX_OK) {
+ if (status != NETDEV_TX_OK && status != NET_XMIT_DROP) {
skb_queue_tail(&npinfo->txq, skb);
schedule_delayed_work(&npinfo->tx_work,0);
}
--
2.7.4
