[Lucid CVE-2012-6539] net: fix info leak in compat dev_ifconf()

Luis Henriques luis.henriques at canonical.com
Fri Mar 22 13:48:42 UTC 2013

From: Mathias Krause <minipli at googlemail.com>


BugLink: http://bugs.launchpad.net/bugs/1156728

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 at googlemail.com>
Signed-off-by: David S. Miller <davem at davemloft.net>
(cherry picked from commit 43da5f2e0d0c69ded3d51907d9552310a6b545e8)

Signed-off-by: Luis Henriques <luis.henriques at canonical.com>

 fs/compat_ioctl.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/fs/compat_ioctl.c b/fs/compat_ioctl.c
index d84e705..c30134b 100644
--- a/fs/compat_ioctl.c
+++ b/fs/compat_ioctl.c
@@ -350,6 +350,7 @@ static int dev_ifconf(unsigned int fd, unsigned int cmd, unsigned long arg)
 	if (copy_from_user(&ifc32, compat_ptr(arg), sizeof(struct ifconf32)))
 		return -EFAULT;
+	memset(&ifc, 0, sizeof(ifc));
 	if (ifc32.ifcbuf == 0) {
 		ifc32.ifc_len = 0;
 		ifc.ifc_len = 0;

More information about the kernel-team mailing list