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devcgroup: fix race against rmdir()

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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: Li Zefan <lizf@cn.fujitsu.com>
Acked-by: Serge Hallyn <serue@us.ibm.com>
Cc: Paul Menage <menage@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Li Zefan 2008-09-02 14:35:52 -07:00 committed by Linus Torvalds
parent 09a2910e54
commit 36fd71d293
1 changed files with 9 additions and 9 deletions
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18
security/device_cgroup.c
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@ -508,12 +508,11 @@ int devcgroup_inode_permission(struct inode *inode, int mask)
return 0; return 0;
if (!S_ISBLK(inode->i_mode) && !S_ISCHR(inode->i_mode)) if (!S_ISBLK(inode->i_mode) && !S_ISCHR(inode->i_mode))
return 0; return 0;
dev_cgroup = css_to_devcgroup(task_subsys_state(current,
devices_subsys_id));
if (!dev_cgroup)
return 0;
rcu_read_lock(); rcu_read_lock();
dev_cgroup = task_devcgroup(current);
list_for_each_entry_rcu(wh, &dev_cgroup->whitelist, list) { list_for_each_entry_rcu(wh, &dev_cgroup->whitelist, list) {
if (wh->type & DEV_ALL) if (wh->type & DEV_ALL)
goto acc_check; goto acc_check;
@ -533,6 +532,7 @@ acc_check:
rcu_read_unlock(); rcu_read_unlock();
return 0; return 0;
} }
rcu_read_unlock(); rcu_read_unlock();
return -EPERM; return -EPERM;
@ -543,12 +543,10 @@ int devcgroup_inode_mknod(int mode, dev_t dev)
struct dev_cgroup *dev_cgroup; struct dev_cgroup *dev_cgroup;
struct dev_whitelist_item *wh; 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(); rcu_read_lock();
dev_cgroup = task_devcgroup(current);
list_for_each_entry(wh, &dev_cgroup->whitelist, list) { list_for_each_entry(wh, &dev_cgroup->whitelist, list) {
if (wh->type & DEV_ALL) if (wh->type & DEV_ALL)
goto acc_check; goto acc_check;
@ -566,6 +564,8 @@ acc_check:
rcu_read_unlock(); rcu_read_unlock();
return 0; return 0;
} }
rcu_read_unlock(); rcu_read_unlock();
return -EPERM; return -EPERM;
} }