net/tun: fix ioctl() based info leaks

[ Upstream commits a117dacde0288f3ec60b6e5bcedae8fa37ee0dfc
  and 8bbb181308bc348e02bfdbebdedd4e4ec9d452ce ]

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>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index 7bea9c65119e339326155c45e4af6e268bda0c6c..a12c9bffb1fa4e72711e5d2bd9a7d1021ee69f45 100644 (file)
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -1243,10 +1243,12 @@ 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?".
                 * This is needed because we never checked for invalid flags on