From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christian Brauner Subject: [PATCH v4 4/6] cgroup: add cgroup_may_write() helper Date: Fri, 17 Jan 2020 19:12:17 +0100 Message-ID: <20200117181219.14542-5-christian.brauner@ubuntu.com> References: <20200117181219.14542-1-christian.brauner@ubuntu.com> Mime-Version: 1.0 Content-Transfer-Encoding: 8bit Return-path: In-Reply-To: <20200117181219.14542-1-christian.brauner-GeWIH/nMZzLQT0dZR+AlfA@public.gmane.org> Sender: linux-api-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: linux-api-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Tejun Heo Cc: Oleg Nesterov , Christian Brauner , Johannes Weiner , Li Zefan , cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: linux-api@vger.kernel.org Add a cgroup_may_write() helper which we can use in the CLONE_INTO_CGROUP patch series to verify that we can write to the destination cgroup. Cc: Tejun Heo Cc: Johannes Weiner Cc: Li Zefan Cc: cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org Signed-off-by: Christian Brauner --- /* v1 */ patch not present /* v2 */ patch not present /* v3 */ patch not present /* v4 */ patch introduced --- kernel/cgroup/cgroup.c | 24 +++++++++++++++++------- 1 file changed, 17 insertions(+), 7 deletions(-) diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c index 49d8cf087e10..b110b435ae49 100644 --- a/kernel/cgroup/cgroup.c +++ b/kernel/cgroup/cgroup.c @@ -4649,13 +4649,28 @@ static int cgroup_procs_show(struct seq_file *s, void *v) return 0; } +static int cgroup_may_write(const struct cgroup *cgrp, struct super_block *sb) +{ + int ret; + struct inode *inode; + + lockdep_assert_held(&cgroup_mutex); + + inode = kernfs_get_inode(sb, cgrp->procs_file.kn); + if (!inode) + return -ENOMEM; + + ret = inode_permission(inode, MAY_WRITE); + iput(inode); + return ret; +} + static int cgroup_procs_write_permission(struct cgroup *src_cgrp, struct cgroup *dst_cgrp, struct super_block *sb) { struct cgroup_namespace *ns = current->nsproxy->cgroup_ns; struct cgroup *com_cgrp = src_cgrp; - struct inode *inode; int ret; lockdep_assert_held(&cgroup_mutex); @@ -4665,12 +4680,7 @@ static int cgroup_procs_write_permission(struct cgroup *src_cgrp, com_cgrp = cgroup_parent(com_cgrp); /* %current should be authorized to migrate to the common ancestor */ - inode = kernfs_get_inode(sb, com_cgrp->procs_file.kn); - if (!inode) - return -ENOMEM; - - ret = inode_permission(inode, MAY_WRITE); - iput(inode); + ret = cgroup_may_write(com_cgrp, sb); if (ret) return ret; -- 2.25.0