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Commit 36fd71d2 authored by Li Zefan's avatar Li Zefan Committed by Linus Torvalds
Browse files

devcgroup: fix race against rmdir() 



During the use of a dev_cgroup, we should guarantee the corresponding
cgroup won't be deleted (i.e.  via rmdir).  This can be done through
css_get(&dev_cgroup->css), but here we can just get and use the dev_cgroup
under rcu_read_lock.

And also remove checking NULL dev_cgroup, it won't be NULL since a task
always belongs to a cgroup.

Signed-off-by: default avatarLi Zefan <lizf@cn.fujitsu.com>
Acked-by: default avatarSerge Hallyn <serue@us.ibm.com>
Cc: Paul Menage <menage@google.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 09a2910e

security/device_cgroup.c

+9 −9
Original line number Diff line number Diff line
@@ -508,12 +508,11 @@ int devcgroup_inode_permission(struct inode *inode, int mask) 
		return 0;

	if (!S_ISBLK(inode->i_mode) && !S_ISCHR(inode->i_mode))

		return 0;

	dev_cgroup = css_to_devcgroup(task_subsys_state(current,

				devices_subsys_id));

	if (!dev_cgroup)

		return 0;



	rcu_read_lock();



	dev_cgroup = task_devcgroup(current);



	list_for_each_entry_rcu(wh, &dev_cgroup->whitelist, list) {

		if (wh->type & DEV_ALL)

			goto acc_check;
@@ -533,6 +532,7 @@ int devcgroup_inode_permission(struct inode *inode, int mask) 
		rcu_read_unlock();

		return 0;

	}



	rcu_read_unlock();



	return -EPERM;
@@ -543,12 +543,10 @@ int devcgroup_inode_mknod(int mode, dev_t dev) 
	struct dev_cgroup *dev_cgroup;

	struct dev_whitelist_item *wh;



	dev_cgroup = css_to_devcgroup(task_subsys_state(current,

				devices_subsys_id));

	if (!dev_cgroup)

		return 0;



	rcu_read_lock();



	dev_cgroup = task_devcgroup(current);



	list_for_each_entry(wh, &dev_cgroup->whitelist, list) {

		if (wh->type & DEV_ALL)

			goto acc_check;
@@ -566,6 +564,8 @@ int devcgroup_inode_mknod(int mode, dev_t dev) 
		rcu_read_unlock();

		return 0;

	}



	rcu_read_unlock();



	return -EPERM;

}