[PATCH v6 1/6] cgroup: unify attach permission checking
From: Christian Brauner <hidden>
Date: 2020-02-05 13:26:51
Also in:
cgroups, lkml
Subsystem:
control group (cgroup), the rest · Maintainers:
Tejun Heo, Johannes Weiner, Michal Koutný, Linus Torvalds
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 <redacted> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: cgroups@vger.kernel.org Acked-by: Michal Koutný <mkoutny@suse.com> Signed-off-by: Christian Brauner <redacted> --- /* v1 */ Link: https://lore.kernel.org/r/20191218173516.7875-2-christian.brauner@ubuntu.com (local) /* v2 */ Link: https://lore.kernel.org/r/20191223061504.28716-2-christian.brauner@ubuntu.com (local) - Christian Brauner [off-list ref]: - Fix return value of cgroup_attach_permissions. It used to return 0 when it should've returned -EOPNOTSUPP. - Fix call to cgroup_attach_permissions() in cgroup_procs_write(). It accidently specified that a thread was moved causing an additional check for domain-group equality to be executed that is not needed. /* v3 */ Link: https://lore.kernel.org/r/20200117002143.15559-2-christian.brauner@ubuntu.com (local) unchanged /* v4 */ Link: https://lore.kernel.org/r/20200117181219.14542-2-christian.brauner@ubuntu.com (local) unchanged /* v5 */ Link: https://lore.kernel.org/r/20200121154844.411-2-christian.brauner@ubuntu.com (local) unchanged /* v6 */ - Michal Koutný [off-list ref]: - Invert logic to use threadgroup argument to match other codepaths. --- kernel/cgroup/cgroup.c | 39 +++++++++++++++++++++++++-------------- 1 file changed, 25 insertions(+), 14 deletions(-)
diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c
index 735af8f15f95..5f84177e2065 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 +4686,26 @@ static int cgroup_procs_write_permission(struct cgroup *src_cgrp, return 0; } +static int cgroup_attach_permissions(struct cgroup *src_cgrp, + struct cgroup *dst_cgrp, + struct super_block *sb, bool threadgroup) +{ + int ret = 0; + + 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 (!threadgroup && (src_cgrp->dom_cgrp != dst_cgrp->dom_cgrp)) + ret = -EOPNOTSUPP; + + return ret; +} + static ssize_t cgroup_procs_write(struct kernfs_open_file *of, char *buf, size_t nbytes, loff_t off) {
@@ -4712,8 +4728,8 @@ 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 +4773,11 @@ 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, false); 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:
--
2.25.0