[ I'm sorry, apparently I had sent the wrong version of this patch. Here is the correct one from https://git.kernel.org/cgit/linux/kernel/git/sergeh/linux-security.git/commit/?h=2016-04-17/kernfs.show&id=79f784037098fddae92258579ef494537a12f1b2 Thanks Michael for pointing that out ] Since we're getting current's cgroup namespace info, and are not modifying it, we don't need the cgroup_mutex. Signed-off-by: Serge Hallyn <serge.hallyn@xxxxxxxxxx> --- kernel/cgroup.c | 40 ++++++++++++++++++++++++++++++++++++---- 1 file changed, 36 insertions(+), 4 deletions(-) diff --git a/kernel/cgroup.c b/kernel/cgroup.c index 9a0d7b3..1243e3e 100644 --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -1215,6 +1215,41 @@ static void cgroup_destroy_root(struct cgroup_root *root) cgroup_free_root(root); } +/* + * look up cgroup associated with current task's cgroup namespace on the + * specified hierarchy + */ +static struct cgroup * +current_cgns_cgroup_from_root(struct cgroup_root *root) +{ + struct cgroup *res = NULL; + struct css_set *cset; + + lockdep_assert_held(&css_set_lock); + + rcu_read_lock(); + + cset = current->nsproxy->cgroup_ns->root_cset; + if (cset == &init_css_set) { + res = &root->cgrp; + } else { + struct cgrp_cset_link *link; + + list_for_each_entry(link, &cset->cgrp_links, cgrp_link) { + struct cgroup *c = link->cgrp; + + if (c->root == root) { + res = c; + break; + } + } + } + rcu_read_unlock(); + + BUG_ON(!res); + return res; +} + /* look up cgroup associated with given css_set on the specified hierarchy */ static struct cgroup *cset_cgroup_from_root(struct css_set *cset, struct cgroup_root *root) @@ -1598,13 +1633,11 @@ static int cgroup_show_path(struct seq_file *sf, struct kernfs_node *kf_node, { int len = 0, ret = 0; char *buf = NULL; - struct cgroup_namespace *ns = current->nsproxy->cgroup_ns; struct cgroup_root *kf_cgroot = cgroup_root_from_kf(kf_root); struct cgroup *ns_cgroup; - mutex_lock(&cgroup_mutex); spin_lock_bh(&css_set_lock); - ns_cgroup = cset_cgroup_from_root(ns->root_cset, kf_cgroot); + ns_cgroup = current_cgns_cgroup_from_root(kf_cgroot); len = kernfs_path_from_node(kf_node, ns_cgroup->kn, NULL, 0); if (len > 0) buf = kmalloc(len + 1, GFP_ATOMIC); @@ -1612,7 +1645,6 @@ static int cgroup_show_path(struct seq_file *sf, struct kernfs_node *kf_node, ret = kernfs_path_from_node(kf_node, ns_cgroup->kn, buf, len + 1); spin_unlock_bh(&css_set_lock); - mutex_unlock(&cgroup_mutex); if (len <= 0) return len; -- 2.7.4 -- To unsubscribe from this list: send the line "unsubscribe linux-api" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
