From: Li Zefan Date: Tue, 2 Sep 2008 21:35:52 +0000 (-0700) Subject: devcgroup: fix race against rmdir() X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=36fd71d293898a59b14e49da1f6e81c1a58f2035;p=GitHub%2FLineageOS%2FG12%2Fandroid_kernel_amlogic_linux-4.9.git 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: Li Zefan Acked-by: Serge Hallyn Cc: Paul Menage Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- diff --git a/security/device_cgroup.c b/security/device_cgroup.c index 7bd296cca041..46f23971f7e4 100644 --- a/security/device_cgroup.c +++ b/security/device_cgroup.c @@ -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; }