Commit f3553220 authored by Christian Brauner's avatar Christian Brauner Committed by Tejun Heo
Browse files

cgroup: add cgroup_may_write() helper 



Add a cgroup_may_write() helper which we can use in the
CLONE_INTO_CGROUP patch series to verify that we can write to the
destination cgroup.

Cc: Tejun Heo <tj@kernel.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Li Zefan <lizefan@huawei.com>
Cc: cgroups@vger.kernel.org
Signed-off-by: default avatarChristian Brauner <christian.brauner@ubuntu.com>
Signed-off-by: default avatarTejun Heo <tj@kernel.org>
parent 5a5cf5cb

kernel/cgroup/cgroup.c

+17 −7
Original line number Diff line number Diff line
@@ -4654,13 +4654,28 @@ static int cgroup_procs_show(struct seq_file *s, void *v) 
	return 0;

}



static int cgroup_may_write(const struct cgroup *cgrp, struct super_block *sb)

{

	int ret;

	struct inode *inode;



	lockdep_assert_held(&cgroup_mutex);



	inode = kernfs_get_inode(sb, cgrp->procs_file.kn);

	if (!inode)

		return -ENOMEM;



	ret = inode_permission(inode, MAY_WRITE);

	iput(inode);

	return ret;

}



static int cgroup_procs_write_permission(struct cgroup *src_cgrp,

					 struct cgroup *dst_cgrp,

					 struct super_block *sb)

{

	struct cgroup_namespace *ns = current->nsproxy->cgroup_ns;

	struct cgroup *com_cgrp = src_cgrp;

	struct inode *inode;

	int ret;



	lockdep_assert_held(&cgroup_mutex);
@@ -4670,12 +4685,7 @@ static int cgroup_procs_write_permission(struct cgroup *src_cgrp, 
		com_cgrp = cgroup_parent(com_cgrp);



	/* %current should be authorized to migrate to the common ancestor */

	inode = kernfs_get_inode(sb, com_cgrp->procs_file.kn);

	if (!inode)

		return -ENOMEM;



	ret = inode_permission(inode, MAY_WRITE);

	iput(inode);

	ret = cgroup_may_write(com_cgrp, sb);

	if (ret)

		return ret;

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