cgroup: fail if monitored file and event_control are in different cgroup (f169007b) · Commits · 戴 / test

If we pass fd of memory.usage_in_bytes of cgroup A to cgroup.event_control of cgroup B, then we won't get memory usage notification from A but B! What's worse, if A and B are in different mount hierarchy, we'll end up accessing NULL pointer! Disallow this kind of invalid usage. Signed-off-by:

Li Zefan <lizefan@huawei.com> Acked-by:

Kirill A. Shutemov <kirill@shutemov.name> Signed-off-by:

Tejun Heo <tj@kernel.org>

kernel/cgroup.c

+11 −0

Original line number	Diff line number	Diff line
		@@ -3856,6 +3856,7 @@ static int cgroup_write_event_control(struct cgroup cgrp, struct cftype cft,
		const char *buffer)
		{
		struct cgroup_event *event = NULL;
		struct cgroup *cgrp_cfile;
		unsigned int efd, cfd;
		struct file *efile = NULL;
		struct file *cfile = NULL;
		@@ -3911,6 +3912,16 @@ static int cgroup_write_event_control(struct cgroup cgrp, struct cftype cft,
		goto fail;
		}

		/*
		* The file to be monitored must be in the same cgroup as
		* cgroup.event_control is.
		*/
		cgrp_cfile = __d_cgrp(cfile->f_dentry->d_parent);
		if (cgrp_cfile != cgrp) {
		ret = -EINVAL;
		goto fail;
		}

		if (!event->cft->register_event \|\| !event->cft->unregister_event) {
		ret = -EINVAL;
		goto fail;

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