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cgroup-v1: Correct privileges check in release_agent writes
commit467a726b75
upstream. The idea is to check: a) the owning user_ns of cgroup_ns, b) capabilities in init_user_ns. The commit24f6008564
("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:24f6008564
("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 <mkoutny@suse.com> Reviewed-by: Masami Ichikawa(CIP) <masami.ichikawa@cybertrust.co.jp> Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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824a950c3f
commit
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1 changed files with 4 additions and 2 deletions
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@ -544,6 +544,7 @@ static ssize_t cgroup_release_agent_write(struct kernfs_open_file *of,
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char *buf, size_t nbytes, loff_t off)
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{
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struct cgroup *cgrp;
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struct cgroup_file_ctx *ctx;
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BUILD_BUG_ON(sizeof(cgrp->root->release_agent_path) < PATH_MAX);
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@ -551,8 +552,9 @@ static ssize_t cgroup_release_agent_write(struct kernfs_open_file *of,
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* Release agent gets called with all capabilities,
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* require capabilities to set release agent.
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*/
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if ((of->file->f_cred->user_ns != &init_user_ns) ||
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!capable(CAP_SYS_ADMIN))
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ctx = of->priv;
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if ((ctx->ns->user_ns != &init_user_ns) ||
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!file_ns_capable(of->file, &init_user_ns, CAP_SYS_ADMIN))
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return -EPERM;
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cgrp = cgroup_kn_lock_live(of->kn, false);
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