[PATCH 4.14 47/68] net: tun: set tun->dev->addr_len during TUNSETLINK processing

Greg Kroah-Hartman
2021-04-15T15:05:07Z

From: Phillip Potter <phil@philpotter.co.uk>

commit cca8ea3b05c972ffb5295367e6c544369b45fbdd upstream.

When changing type with TUNSETLINK ioctl command, set tun->dev->addr_len
to match the appropriate type, using new tun_get_addr_len utility function
which returns appropriate address length for given type. Fixes a
KMSAN-found uninit-value bug reported by syzbot at:
https://syzkaller.appspot.com/bug?id=0766d38c656abeace60621896d705743aeefed51

Reported-by: syzbot+001516d86dbe88862cec@syzkaller.appspotmail.com
Diagnosed-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Phillip Potter <phil@philpotter.co.uk>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/net/tun.c | 48 ++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 48 insertions(+)

--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -75,6 +75,14 @@
#include <linux/skb_array.h>
#include <linux/bpf.h>
#include <linux/bpf_trace.h>
+#include <linux/ieee802154.h>
+#include <linux/if_ltalk.h>
+#include <uapi/linux/if_fddi.h>
+#include <uapi/linux/if_hippi.h>
+#include <uapi/linux/if_fc.h>
+#include <net/ax25.h>
+#include <net/rose.h>
+#include <net/6lowpan.h>

#include <linux/uaccess.h>

@@ -2292,6 +2300,45 @@ unlock:
return ret;
}

+/* Return correct value for tun->dev->addr_len based on tun->dev->type. */
+static unsigned char tun_get_addr_len(unsigned short type)
+{
+ switch (type) {
+ case ARPHRD_IP6GRE:
+ case ARPHRD_TUNNEL6:
+ return sizeof(struct in6_addr);
+ case ARPHRD_IPGRE:
+ case ARPHRD_TUNNEL:
+ case ARPHRD_SIT:
+ return 4;
+ case ARPHRD_ETHER:
+ return ETH_ALEN;
+ case ARPHRD_IEEE802154:
+ case ARPHRD_IEEE802154_MONITOR:
+ return IEEE802154_EXTENDED_ADDR_LEN;
+ case ARPHRD_PHONET_PIPE:
+ case ARPHRD_PPP:
+ case ARPHRD_NONE:
+ return 0;
+ case ARPHRD_6LOWPAN:
+ return EUI64_ADDR_LEN;
+ case ARPHRD_FDDI:
+ return FDDI_K_ALEN;
+ case ARPHRD_HIPPI:
+ return HIPPI_ALEN;
+ case ARPHRD_IEEE802:
+ return FC_ALEN;
+ case ARPHRD_ROSE:
+ return ROSE_ADDR_LEN;
+ case ARPHRD_NETROM:
+ return AX25_ADDR_LEN;
+ case ARPHRD_LOCALTLK:
+ return LTALK_ALEN;
+ default:
+ return 0;
+ }
+}
+
static long __tun_chr_ioctl(struct file *file, unsigned int cmd,
unsigned long arg, int ifreq_len)
{
@@ -2434,6 +2481,7 @@ static long __tun_chr_ioctl(struct file
ret = -EBUSY;
} else {
tun->dev->type = (int) arg;
+ tun->dev->addr_len = tun_get_addr_len(tun->dev->type);
tun_debug(KERN_INFO, tun, "linktype set to %d\n",
tun->dev->type);
ret = 0;