net: tun: set tun->dev->addr_len during TUNSETLINK processing

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>

diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index fc86da7..4cf38be 100644 (file)
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -69,6 +69,14 @@
 #include <linux/bpf.h>
 #include <linux/bpf_trace.h>
 #include <linux/mutex.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>
 #include <linux/proc_fs.h>
@@ -2919,6 +2927,45 @@ static int tun_set_ebpf(struct tun_struct *tun, struct tun_prog __rcu **prog_p,
        return __tun_set_ebpf(tun, prog_p, prog);
 }
 
+/* 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)
 {
@@ -3082,6 +3129,7 @@ static long __tun_chr_ioctl(struct file *file, unsigned int cmd,
                                break;
                        }
                        tun->dev->type = (int) arg;
+                       tun->dev->addr_len = tun_get_addr_len(tun->dev->type);
                        netif_info(tun, drv, tun->dev, "linktype set to %d\n",
                                   tun->dev->type);
                        call_netdevice_notifiers(NETDEV_POST_TYPE_CHANGE,