net: fix info leak in compat dev_ifconf()

[ Upstream commit 43da5f2e0d0c69ded3d51907d9552310a6b545e8 ]

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: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/net/socket.c b/net/socket.c
index cf41afcc89bba4314411d9c392af1463bf39e099..1b0f0fccdbcd0c37cb9d5565c3d4bed527a8a522 100644 (file)
--- a/net/socket.c
+++ b/net/socket.c
@@ -2645,6 +2645,7 @@ 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;