From 68f7cc3123a55ec435b4a72f50c411718b226f62 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Michal=20Koutn=C3=BD?= Date: Tue, 28 Jun 2022 11:36:18 +0800 Subject: [PATCH] cgroup-v1: Correct privileges check in release_agent writes MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit stable inclusion from stable-v5.10.109 commit ea21245cdcab3f2b46aecd421ac5f5753a1cf88d bugzilla: https://gitee.com/openeuler/kernel/issues/I574AE Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=ea21245cdcab3f2b46aecd421ac5f5753a1cf88d -------------------------------- commit 467a726b754f474936980da793b4ff2ec3e382a7 upstream. The idea is to check: a) the owning user_ns of cgroup_ns, b) capabilities in init_user_ns. The commit 24f600856418 ("cgroup-v1: Require capabilities to set release_agent") got this wrong in the write handler of release_agent since it checked user_ns of the opener (may be different from the owning user_ns of cgroup_ns). Secondly, to avoid possibly confused deputy, the capability of the opener must be checked. Fixes: 24f600856418 ("cgroup-v1: Require capabilities to set release_agent") Cc: stable@vger.kernel.org Link: https://lore.kernel.org/stable/20220216121142.GB30035@blackbody.suse.cz/ Signed-off-by: Michal Koutný Reviewed-by: Masami Ichikawa(CIP) Signed-off-by: Tejun Heo Signed-off-by: Greg Kroah-Hartman Signed-off-by: Yu Liao Reviewed-by: Wei Li Signed-off-by: Zheng Zengkai --- kernel/cgroup/cgroup-v1.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/kernel/cgroup/cgroup-v1.c b/kernel/cgroup/cgroup-v1.c index ff965ca9ca21..be884bc2ae61 100644 --- a/kernel/cgroup/cgroup-v1.c +++ b/kernel/cgroup/cgroup-v1.c @@ -545,6 +545,7 @@ static ssize_t cgroup_release_agent_write(struct kernfs_open_file *of, char *buf, size_t nbytes, loff_t off) { struct cgroup *cgrp; + struct cgroup_file_ctx *ctx; BUILD_BUG_ON(sizeof(cgrp->root->release_agent_path) < PATH_MAX); @@ -552,8 +553,9 @@ static ssize_t cgroup_release_agent_write(struct kernfs_open_file *of, * Release agent gets called with all capabilities, * require capabilities to set release agent. */ - if ((of->file->f_cred->user_ns != &init_user_ns) || - !capable(CAP_SYS_ADMIN)) + ctx = of->priv; + if ((ctx->ns->user_ns != &init_user_ns) || + !file_ns_capable(of->file, &init_user_ns, CAP_SYS_ADMIN)) return -EPERM; cgrp = cgroup_kn_lock_live(of->kn, false); -- GitLab