| From | Ben Hutchings <> | Date | Mon, 21 Oct 2013 09:46:28 +0100 | Subject | [PATCH 3.2 131/149] cgroup: fail if monitored file and event_control are in different cgroup |
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3.2.52-rc1 review patch. If anyone has any objections, please let me know.
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From: Li Zefan <lizefan@huawei.com>
commit f169007b2773f285e098cb84c74aac0154d65ff7 upstream.
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> Signed-off-by: Ben Hutchings <ben@decadent.org.uk> --- kernel/cgroup.c | 11 +++++++++++ 1 file changed, 11 insertions(+)
--- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -3504,6 +3504,7 @@ static int cgroup_write_event_control(st const char *buffer) { struct cgroup_event *event = NULL; + struct cgroup *cgrp_cfile; unsigned int efd, cfd; struct file *efile = NULL; struct file *cfile = NULL; @@ -3559,6 +3560,16 @@ static int cgroup_write_event_control(st 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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