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net: fix info leak in compat dev_ifconf()

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 <>
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1 parent 2d8a041 commit 43da5f2e0d0c69ded3d51907d9552310a6b545e8 @minipli minipli committed with davem330 Aug 15, 2012
Showing with 1 addition and 0 deletions.
  1. +1 −0 net/socket.c
@@ -2657,6 +2657,7 @@ 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;

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