Commit 031a3cd4 authored by Guillaume Nault's avatar Guillaume Nault Committed by Ben Hutchings

ppp: ensure file->private_data can't be overridden

commit e8e56ffd upstream.

Locking ppp_mutex must be done before dereferencing file->private_data,
otherwise it could be modified before ppp_unattached_ioctl() takes the
lock. This could lead ppp_unattached_ioctl() to override ->private_data,
thus leaking reference to the ppp_file previously pointed to.

v2: lock all ppp_ioctl() instead of just checking private_data in
    ppp_unattached_ioctl(), to avoid ambiguous behaviour.

Fixes: f3ff8a4d ("ppp: push BKL down into the driver")
Signed-off-by: default avatarGuillaume Nault <g.nault@alphalink.fr>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
Signed-off-by: default avatarBen Hutchings <ben@decadent.org.uk>
parent 31a055ab
......@@ -561,7 +561,7 @@ static int get_filter(void __user *arg, struct sock_filter **p)
static long ppp_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
{
struct ppp_file *pf = file->private_data;
struct ppp_file *pf;
struct ppp *ppp;
int err = -EFAULT, val, val2, i;
struct ppp_idle idle;
......@@ -571,9 +571,14 @@ static long ppp_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
void __user *argp = (void __user *)arg;
int __user *p = argp;
if (!pf)
return ppp_unattached_ioctl(current->nsproxy->net_ns,
mutex_lock(&ppp_mutex);
pf = file->private_data;
if (!pf) {
err = ppp_unattached_ioctl(current->nsproxy->net_ns,
pf, file, cmd, arg);
goto out;
}
if (cmd == PPPIOCDETACH) {
/*
......@@ -588,7 +593,6 @@ static long ppp_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
* this fd and reopening /dev/ppp.
*/
err = -EINVAL;
mutex_lock(&ppp_mutex);
if (pf->kind == INTERFACE) {
ppp = PF_TO_PPP(pf);
if (file == ppp->owner)
......@@ -600,15 +604,13 @@ static long ppp_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
} else
pr_warn("PPPIOCDETACH file->f_count=%ld\n",
atomic_long_read(&file->f_count));
mutex_unlock(&ppp_mutex);
return err;
goto out;
}
if (pf->kind == CHANNEL) {
struct channel *pch;
struct ppp_channel *chan;
mutex_lock(&ppp_mutex);
pch = PF_TO_CHANNEL(pf);
switch (cmd) {
......@@ -630,17 +632,16 @@ static long ppp_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
err = chan->ops->ioctl(chan, cmd, arg);
up_read(&pch->chan_sem);
}
mutex_unlock(&ppp_mutex);
return err;
goto out;
}
if (pf->kind != INTERFACE) {
/* can't happen */
pr_err("PPP: not interface or channel??\n");
return -EINVAL;
err = -EINVAL;
goto out;
}
mutex_lock(&ppp_mutex);
ppp = PF_TO_PPP(pf);
switch (cmd) {
case PPPIOCSMRU:
......@@ -811,7 +812,10 @@ static long ppp_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
default:
err = -ENOTTY;
}
out:
mutex_unlock(&ppp_mutex);
return err;
}
......@@ -824,7 +828,6 @@ static int ppp_unattached_ioctl(struct net *net, struct ppp_file *pf,
struct ppp_net *pn;
int __user *p = (int __user *)arg;
mutex_lock(&ppp_mutex);
switch (cmd) {
case PPPIOCNEWUNIT:
/* Create a new ppp unit */
......@@ -875,7 +878,7 @@ static int ppp_unattached_ioctl(struct net *net, struct ppp_file *pf,
default:
err = -ENOTTY;
}
mutex_unlock(&ppp_mutex);
return err;
}
......
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