On 2019/4/23 下午2:00, Cong Wang wrote:
On Mon, Apr 22, 2019 at 2:41 AM Jason Wang <[email protected]> wrote:
On 2019/4/22 上午11:57, YueHaibing wrote:
We get a KASAN report as below, but don't have any reproducer.
Any comments are appreciated.
==================================================================
BUG: KASAN: use-after-free in tun_net_xmit+0x1670/0x1750 drivers/net/tun.c:1104
Read of size 8 at addr ffff88836cc26a70 by task swapper/3/0
Which kernel version did you use? The calltrace points out the a use
after free for tun_file structure which should be synchronized through
RCU + RTNL lock.
The tfile socket has to be marked with SOCK_RCU_FREE in order
to fully respect the RCU grace period.
diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index e9ca1c088d0b..31c3210288cb 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -3431,6 +3431,7 @@ static int tun_chr_open(struct inode *inode,
struct file * file)
file->private_data = tfile;
INIT_LIST_HEAD(&tfile->next);
+ sock_set_flag(&tfile->sk, SOCK_RCU_FREE);
sock_set_flag(&tfile->sk, SOCK_ZEROCOPY);
return 0;
We did a synchronize_net() when socket is detached from netdevice in
__tun_detach() so it looks to me this is unnecessary.
But if it solves the use-after-free, it means we have bugs somewhere.
Thanks
