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Subject[ 156/184] net: fix info leak in compat dev_ifconf()
2.6.32-longterm review patch.  If anyone has any objections, please let me know.


From: Mathias Krause <>

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 <>
Signed-off-by: David S. Miller <>
[bwh: Backported to 2.6.32: adjust filename, context]
Signed-off-by: Willy Tarreau <>
fs/compat_ioctl.c | 1 +
1 file changed, 1 insertion(+)

diff --git a/fs/compat_ioctl.c b/fs/compat_ioctl.c
index 0dd21a4..98d3c58 100644
--- a/fs/compat_ioctl.c
+++ b/fs/compat_ioctl.c
@@ -352,6 +352,7 @@ 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;

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