From: Michal Koutný Date: Thu, 17 Feb 2022 16:11:28 +0000 (+0100) Subject: cgroup-v1: Correct privileges check in release_agent writes X-Git-Tag: baikal/aarch64/sdk6.1~4618^2~1 X-Git-Url: https://git.baikalelectronics.ru/sdk/?a=commitdiff_plain;h=6b344a2a126484c9f1fa58e50bd1704b32b9cc90;p=kernel.git cgroup-v1: Correct privileges check in release_agent writes The idea is to check: a) the owning user_ns of cgroup_ns, b) capabilities in init_user_ns. The commit 3ae097a730e6 ("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: 3ae097a730e6 ("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 --- diff --git a/kernel/cgroup/cgroup-v1.c b/kernel/cgroup/cgroup-v1.c index 0e877dbcfeea9..afc6c0e9c966e 100644 --- a/kernel/cgroup/cgroup-v1.c +++ b/kernel/cgroup/cgroup-v1.c @@ -546,6 +546,7 @@ 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); @@ -553,8 +554,9 @@ 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);