From f3553220d4cc458d69f7da6e71a3a6097778bd28 Mon Sep 17 00:00:00 2001
From: Christian Brauner <christian.brauner@ubuntu.com>
Date: Wed, 5 Feb 2020 14:26:21 +0100
Subject: [PATCH] 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: Christian Brauner <christian.brauner@ubuntu.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
---
kernel/cgroup/cgroup.c | 24 +++++++++++++++++-------
1 file changed, 17 insertions(+), 7 deletions(-)
diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c
index 502769b2683cd..6d8bdddd8c284 100644
--- a/kernel/cgroup/cgroup.c
+++ b/kernel/cgroup/cgroup.c
@@ -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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