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-rw-r--r--kernel/cgroup.c35
1 files changed, 35 insertions, 0 deletions
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 33a2f63d4a10..9624db80dc4e 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -61,6 +61,7 @@
#include <linux/cpuset.h>
#include <linux/proc_ns.h>
#include <linux/nsproxy.h>
+#include <linux/file.h>
#include <net/sock.h>
/*
@@ -6204,6 +6205,40 @@ struct cgroup *cgroup_get_from_path(const char *path)
}
EXPORT_SYMBOL_GPL(cgroup_get_from_path);
+/**
+ * cgroup_get_from_fd - get a cgroup pointer from a fd
+ * @fd: fd obtained by open(cgroup2_dir)
+ *
+ * Find the cgroup from a fd which should be obtained
+ * by opening a cgroup directory. Returns a pointer to the
+ * cgroup on success. ERR_PTR is returned if the cgroup
+ * cannot be found.
+ */
+struct cgroup *cgroup_get_from_fd(int fd)
+{
+ struct cgroup_subsys_state *css;
+ struct cgroup *cgrp;
+ struct file *f;
+
+ f = fget_raw(fd);
+ if (!f)
+ return ERR_PTR(-EBADF);
+
+ css = css_tryget_online_from_dir(f->f_path.dentry, NULL);
+ fput(f);
+ if (IS_ERR(css))
+ return ERR_CAST(css);
+
+ cgrp = css->cgroup;
+ if (!cgroup_on_dfl(cgrp)) {
+ cgroup_put(cgrp);
+ return ERR_PTR(-EBADF);
+ }
+
+ return cgrp;
+}
+EXPORT_SYMBOL_GPL(cgroup_get_from_fd);
+
/*
* sock->sk_cgrp_data handling. For more info, see sock_cgroup_data
* definition in cgroup-defs.h.