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SubjectRe: [CHECKER] two probable security holes
   From: Ken Ashcraft <>
Date: Tue, 18 Sep 2001 14:29:57 -0700 (PDT)

Watch ifr.ifr_name.

Hi Ken, I believe there is some bug in your new checker algorithms for
this case.

struct ifreq ifr;
int err;
if (copy_from_user(&ifr, (void *)arg, sizeof(ifr)))
return -EFAULT;
ifr.ifr_name[IFNAMSIZ-1] = '\0';

ifreq copied safely to kernel space, ifr.ifr_name[] is inside the
struct and NOT a user pointer.

err = tun_set_iff(file, &ifr);

Pass address of kernel ifreq.

if (*ifr->ifr_name)
name = ifr->ifr_name;

if ((err = dev_alloc_name(&tun->dev, name)) < 0)
goto failed;

Perfectly fine still, name always points to kernel memory.

int dev_alloc_name(struct net_device *dev, const char *name)

for (i = 0; i < 100; i++) {

Still fine, as stated "name" is pointing to kernel memory.

Perhaps your code is being confused by "ifreq->if_name" being
an array.

Franks a lot,
David S. Miller
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