Re: [PATCH 01/20] cgroup: Manual replacement of the deprecated strlcpy() with return values

From: "Michal Koutný" <mkoutny@suse.com>
To: Romain Perier <romain.perier@gmail.com>
Cc: Kees Cook <keescook@chromium.org>,
	kernel-hardening@lists.openwall.com, Tejun Heo <tj@kernel.org>,
	Zefan Li <lizefan.x@bytedance.com>,
	Johannes Weiner <hannes@cmpxchg.org>,
	cgroups@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 01/20] cgroup: Manual replacement of the deprecated strlcpy() with return values
Date: Tue, 23 Feb 2021 17:13:30 +0100	[thread overview]
Message-ID: <YDUpqn+cRWg1ZYYT@blackbook> (raw)
In-Reply-To: <20210222151231.22572-2-romain.perier@gmail.com>

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Hello.

On Mon, Feb 22, 2021 at 04:12:12PM +0100, Romain Perier <romain.perier@gmail.com> wrote:
> --- a/kernel/cgroup/cgroup.c
> +++ b/kernel/cgroup/cgroup.c
> @@ -2265,7 +2265,7 @@ int task_cgroup_path(struct task_struct *task, char *buf, size_t buflen)
Actually, this function isn't used at all. So I'd instead propose the
patch below.

-- >8 --
From 4f7e0b9c0412f60e0b0e8b7d1ef6eb2790dca567 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Michal=20Koutn=C3=BD?= <mkoutny@suse.com>
Date: Tue, 23 Feb 2021 17:05:57 +0100
Subject: [PATCH] cgroup: Drop task_cgroup_path()
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

The function has no current users and it is a remnant from kdbus
enthusiasm era 857a2beb09ab ("cgroup: implement
task_cgroup_path_from_hierarchy()"). Drop it to eliminate unused code.

Suggested-by: Romain Perier <romain.perier@gmail.com>
Signed-off-by: Michal Koutný <mkoutny@suse.com>
---
 include/linux/cgroup.h |  1 -
 kernel/cgroup/cgroup.c | 39 ---------------------------------------
 2 files changed, 40 deletions(-)

diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index 4f2f79de083e..e9c41b15fd4e 100644
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -115,7 +115,6 @@ int cgroup_add_legacy_cftypes(struct cgroup_subsys *ss, struct cftype *cfts);
 int cgroup_rm_cftypes(struct cftype *cfts);
 void cgroup_file_notify(struct cgroup_file *cfile);
 
-int task_cgroup_path(struct task_struct *task, char *buf, size_t buflen);
 int cgroupstats_build(struct cgroupstats *stats, struct dentry *dentry);
 int proc_cgroup_show(struct seq_file *m, struct pid_namespace *ns,
 		     struct pid *pid, struct task_struct *tsk);
diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c
index c80fe99f85ae..d75ffd461222 100644
--- a/kernel/cgroup/cgroup.c
+++ b/kernel/cgroup/cgroup.c
@@ -2235,45 +2235,6 @@ int cgroup_path_ns(struct cgroup *cgrp, char *buf, size_t buflen,
 }
 EXPORT_SYMBOL_GPL(cgroup_path_ns);
 
-/**
- * task_cgroup_path - cgroup path of a task in the first cgroup hierarchy
- * @task: target task
- * @buf: the buffer to write the path into
- * @buflen: the length of the buffer
- *
- * Determine @task's cgroup on the first (the one with the lowest non-zero
- * hierarchy_id) cgroup hierarchy and copy its path into @buf.  This
- * function grabs cgroup_mutex and shouldn't be used inside locks used by
- * cgroup controller callbacks.
- *
- * Return value is the same as kernfs_path().
- */
-int task_cgroup_path(struct task_struct *task, char *buf, size_t buflen)
-{
-	struct cgroup_root *root;
-	struct cgroup *cgrp;
-	int hierarchy_id = 1;
-	int ret;
-
-	mutex_lock(&cgroup_mutex);
-	spin_lock_irq(&css_set_lock);
-
-	root = idr_get_next(&cgroup_hierarchy_idr, &hierarchy_id);
-
-	if (root) {
-		cgrp = task_cgroup_from_root(task, root);
-		ret = cgroup_path_ns_locked(cgrp, buf, buflen, &init_cgroup_ns);
-	} else {
-		/* if no hierarchy exists, everyone is in "/" */
-		ret = strlcpy(buf, "/", buflen);
-	}
-
-	spin_unlock_irq(&css_set_lock);
-	mutex_unlock(&cgroup_mutex);
-	return ret;
-}
-EXPORT_SYMBOL_GPL(task_cgroup_path);
-
 /**
  * cgroup_migrate_add_task - add a migration target task to a migration context
  * @task: target task
-- 
2.30.1


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