From da8ddba566ff0a883237dbc8c5dadef1ca769e19 Mon Sep 17 00:00:00 2001 From: Christian Brauner Date: Wed, 23 Jan 2019 12:41:15 +0100 Subject: binderfs: respect limit on binder control creation We currently adhere to the reserved devices limit when creating new binderfs devices in binderfs instances not located in the inital ipc namespace. But it is still possible to rob the host instances of their 4 reserved devices by creating the maximum allowed number of devices in a single binderfs instance located in a non-initial ipc namespace and then mounting 4 separate binderfs instances in non-initial ipc namespaces. That happens because the limit is currently not respected for the creation of the initial binder-control device node. Block this nonsense by performing the same check in binderfs_binder_ctl_create() that we perform in binderfs_binder_device_create(). Fixes: 36bdf3cae09d ("binderfs: reserve devices for initial mount") Signed-off-by: Christian Brauner Signed-off-by: Greg Kroah-Hartman --- drivers/android/binderfs.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) (limited to 'drivers/android') diff --git a/drivers/android/binderfs.c b/drivers/android/binderfs.c index 6a2185eb66c5..7a550104a722 100644 --- a/drivers/android/binderfs.c +++ b/drivers/android/binderfs.c @@ -395,6 +395,11 @@ static int binderfs_binder_ctl_create(struct super_block *sb) struct inode *inode = NULL; struct dentry *root = sb->s_root; struct binderfs_info *info = sb->s_fs_info; +#if defined(CONFIG_IPC_NS) + bool use_reserve = (info->ipc_ns == &init_ipc_ns); +#else + bool use_reserve = true; +#endif device = kzalloc(sizeof(*device), GFP_KERNEL); if (!device) @@ -413,7 +418,10 @@ static int binderfs_binder_ctl_create(struct super_block *sb) /* Reserve a new minor number for the new device. */ mutex_lock(&binderfs_minors_mutex); - minor = ida_alloc_max(&binderfs_minors, BINDERFS_MAX_MINOR, GFP_KERNEL); + minor = ida_alloc_max(&binderfs_minors, + use_reserve ? BINDERFS_MAX_MINOR : + BINDERFS_MAX_MINOR_CAPPED, + GFP_KERNEL); mutex_unlock(&binderfs_minors_mutex); if (minor < 0) { ret = minor; -- cgit