net: fix info leak in compat dev_ifconf()

commit 43da5f2e0d0c69ded3d51907d9552310a6b545e8 upstream.

The implementation of dev_ifconf() for the compat ioctl interface uses
an intermediate ifc structure allocated in userland for the duration of
the syscall. Though, it fails to initialize the padding bytes inserted
for alignment and that for leaks four bytes of kernel stack. Add an
explicit memset(0) before filling the structure to avoid the info leak.

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

diff --git a/net/socket.c b/net/socket.c
index c802797e3a4abddddbe733e094e1443f3a76cbdb..b0d3b6a025eaf68d2e17c3535e711a64c6bbb6ab 100644 (file)
--- a/net/socket.c
+++ b/net/socket.c
@@ -2508,6 +2508,7 @@ static int dev_ifconf(struct net *net, struct compat_ifconf __user *uifc32)
        if (copy_from_user(&ifc32, uifc32, sizeof(struct compat_ifconf)))
                return -EFAULT;
 
+       memset(&ifc, 0, sizeof(ifc));
        if (ifc32.ifcbuf == 0) {
                ifc32.ifc_len = 0;
                ifc.ifc_len = 0;