From: Christian Brauner <christian.brauner@ubuntu.com>
To: linux-api@vger.kernel.org, linux-kernel@vger.kernel.org,
Tejun Heo <tj@kernel.org>
Cc: Christian Brauner <christian.brauner@ubuntu.com>,
Li Zefan <lizefan@huawei.com>,
Johannes Weiner <hannes@cmpxchg.org>,
cgroups@vger.kernel.org
Subject: [PATCH 1/3] cgroup: unify attach permission checking
Date: Wed, 18 Dec 2019 18:35:14 +0100 [thread overview]
Message-ID: <20191218173516.7875-2-christian.brauner@ubuntu.com> (raw)
In-Reply-To: <20191218173516.7875-1-christian.brauner@ubuntu.com>
The core codepaths to check whether a process can be attached to a
cgroup are the same for threads and thread-group leaders. Only a small
piece of code verifying that source and destination cgroup are in the
same domain differentiates the thread permission checking from
thread-group leader permission checking.
Since cgroup_migrate_vet_dst() only matters cgroup2 - it is a noop on
cgroup1 - we can move it out of cgroup_attach_task().
All checks can now be consolidated into a new helper
cgroup_attach_permissions() callable from both cgroup_procs_write() and
cgroup_threads_write().
Cc: Tejun Heo <tj@kernel.org>
Cc: Li Zefan <lizefan@huawei.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: cgroups@vger.kernel.org
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
---
kernel/cgroup/cgroup.c | 46 +++++++++++++++++++++++++++++-------------
1 file changed, 32 insertions(+), 14 deletions(-)
diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c
index 735af8f15f95..5ee06c1f7456 100644
--- a/kernel/cgroup/cgroup.c
+++ b/kernel/cgroup/cgroup.c
@@ -2719,11 +2719,7 @@ int cgroup_attach_task(struct cgroup *dst_cgrp, struct task_struct *leader,
{
DEFINE_CGROUP_MGCTX(mgctx);
struct task_struct *task;
- int ret;
-
- ret = cgroup_migrate_vet_dst(dst_cgrp);
- if (ret)
- return ret;
+ int ret = 0;
/* look up all src csets */
spin_lock_irq(&css_set_lock);
@@ -4690,6 +4686,33 @@ static int cgroup_procs_write_permission(struct cgroup *src_cgrp,
return 0;
}
+static inline bool cgroup_same_domain(const struct cgroup *src_cgrp,
+ const struct cgroup *dst_cgrp)
+{
+ return src_cgrp->dom_cgrp == dst_cgrp->dom_cgrp;
+}
+
+static int cgroup_attach_permissions(struct cgroup *src_cgrp,
+ struct cgroup *dst_cgrp,
+ struct super_block *sb, bool thread)
+{
+ int ret;
+
+ ret = cgroup_procs_write_permission(src_cgrp, dst_cgrp, sb);
+ if (ret)
+ return ret;
+
+ ret = cgroup_migrate_vet_dst(dst_cgrp);
+ if (ret)
+ return ret;
+
+ if (thread &&
+ !cgroup_same_domain(src_cgrp->dom_cgrp, dst_cgrp->dom_cgrp))
+ ret = -EOPNOTSUPP;
+
+ return 0;
+}
+
static ssize_t cgroup_procs_write(struct kernfs_open_file *of,
char *buf, size_t nbytes, loff_t off)
{
@@ -4712,8 +4735,8 @@ static ssize_t cgroup_procs_write(struct kernfs_open_file *of,
src_cgrp = task_cgroup_from_root(task, &cgrp_dfl_root);
spin_unlock_irq(&css_set_lock);
- ret = cgroup_procs_write_permission(src_cgrp, dst_cgrp,
- of->file->f_path.dentry->d_sb);
+ ret = cgroup_attach_permissions(src_cgrp, dst_cgrp,
+ of->file->f_path.dentry->d_sb, true);
if (ret)
goto out_finish;
@@ -4757,16 +4780,11 @@ static ssize_t cgroup_threads_write(struct kernfs_open_file *of,
spin_unlock_irq(&css_set_lock);
/* thread migrations follow the cgroup.procs delegation rule */
- ret = cgroup_procs_write_permission(src_cgrp, dst_cgrp,
- of->file->f_path.dentry->d_sb);
+ ret = cgroup_attach_permissions(src_cgrp, dst_cgrp,
+ of->file->f_path.dentry->d_sb, true);
if (ret)
goto out_finish;
- /* and must be contained in the same domain */
- ret = -EOPNOTSUPP;
- if (src_cgrp->dom_cgrp != dst_cgrp->dom_cgrp)
- goto out_finish;
-
ret = cgroup_attach_task(dst_cgrp, task, false);
out_finish:
--
2.24.0
next prev parent reply other threads:[~2019-12-18 17:35 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-12-18 17:35 [PATCH 0/3] clone3 & cgroups: allow spawning processes into cgroups Christian Brauner
2019-12-18 17:35 ` Christian Brauner [this message]
2019-12-18 23:46 ` [PATCH 1/3] cgroup: unify attach permission checking Christian Brauner
2019-12-19 0:39 ` Christian Brauner
2019-12-18 17:35 ` [PATCH 2/3] clone3: allow spawning processes into cgroups Christian Brauner
2019-12-20 20:36 ` Oleg Nesterov
2019-12-18 17:35 ` [PATCH 3/3] selftests/cgroup: add tests for cloning " Christian Brauner
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