net/tun: fix ioctl() based info leaks

The tun module leaks up to 36 bytes of memory by not fully initializing
a structure located on the stack that gets copied to user memory by the
TUNGETIFF and SIOCGIFHWADDR ioctl()s.

Signed-off-by: Mathias Krause <minipli@googlemail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 3 insertions, 1 deletions

diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index c62163e272c..f55c4622261 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -1379,9 +1379,11 @@ static long __tun_chr_ioctl(struct file *file, unsigned int cmd,
         int vnet_hdr_sz;
         int ret;
 
-        if (cmd == TUNSETIFF || _IOC_TYPE(cmd) == 0x89)
+        if (cmd == TUNSETIFF || _IOC_TYPE(cmd) == 0x89) {
                 if (copy_from_user(&ifr, argp, ifreq_len))
                         return -EFAULT;
+        } else
+                memset(&ifr, 0, sizeof(ifr));
 
         if (cmd == TUNGETFEATURES) {
                 /* Currently this just means: "what IFF flags are valid?".