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

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: f3ff8a4d80 ("ppp: push BKL down into the driver")
Signed-off-by: Guillaume Nault <g.nault@alphalink.fr>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Guillaume Nault 2016-03-14 21:17:16 +01:00 committed by David S. Miller
parent c8f5d29899
commit e8e56ffd9d
1 changed files with 17 additions and 14 deletions
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29
drivers/net/ppp/ppp_generic.c
View File

@ -575,7 +575,7 @@ 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;
@ -585,9 +585,14 @@ 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) {
/*
@ -602,7 +607,6 @@ 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);
rtnl_lock();
@ -616,15 +620,13 @@ 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) {
@ -646,17 +648,16 @@ 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:
@ -831,7 +832,10 @@ static long ppp_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
default:
err = -ENOTTY;
}
out:
mutex_unlock(&ppp_mutex);
return err;
}
@ -844,7 +848,6 @@ 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 */
@ -894,7 +897,7 @@ static int ppp_unattached_ioctl(struct net *net, struct ppp_file *pf,
default:
err = -ENOTTY;
}
mutex_unlock(&ppp_mutex);
return err;
}