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

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
......@@ -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 @@ acc_check:
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 @@ acc_check:
rcu_read_unlock();
return 0;
}
rcu_read_unlock();
return -EPERM;
}
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