From e8e56ffd9d2973398b60ece1f1bebb8d67b4d032 Mon Sep 17 00:00:00 2001 From: Guillaume Nault Date: Mon, 14 Mar 2016 21:17:16 +0100 Subject: 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: f3ff8a4d80e8 ("ppp: push BKL down into the driver") Signed-off-by: Guillaume Nault Signed-off-by: David S. Miller --- drivers/net/ppp/ppp_generic.c | 31 +++++++++++++++++-------------- 1 file changed, 17 insertions(+), 14 deletions(-) diff --git a/drivers/net/ppp/ppp_generic.c b/drivers/net/ppp/ppp_generic.c index 931836e09a6b..4fd861063ed4 100644 --- a/drivers/net/ppp/ppp_generic.c +++ b/drivers/net/ppp/ppp_generic.c @@ -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, - pf, file, cmd, arg); + 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; } -- cgit v1.2.3