Commit dc5736ed authored Feb 17, 2014 by Li Zefan Committed by Tejun Heo Feb 18, 2014

cgroup: add a validation check to cgroup_add_cftyps()



Fengguang reported this bug:

BUG: unable to handle kernel NULL pointer dereference at 0000003c
IP: [<cc90b4ad>] cgroup_cfts_commit+0x27/0x1c1
...
Call Trace:
  [<cc9d1129>] ? kmem_cache_alloc_trace+0x33f/0x3b7
  [<cc90c6fc>] cgroup_add_cftypes+0x8f/0xca
  [<cd78b646>] cgroup_init+0x6a/0x26a
  [<cd764d7d>] start_kernel+0x4d7/0x57a
  [<cd7642ef>] i386_start_kernel+0x92/0x96

This happens in a corner case. If CGROUP_SCHED=y but CFS_BANDWIDTH=n &&
FAIR_GROUP_SCHED=n && RT_GROUP_SCHED=n, we have:

cpu_files[] = {
	{ }	/* terminate */
}

When we pass cpu_files to cgroup_apply_cftypes(), as cpu_files[0].ss
is NULL, we'll access NULL pointer.

The bug was introduced by commit de00ffa5
("cgroup: make cgroup_subsys->base_cftypes use cgroup_add_cftypes()").

Reported-by: Fengguang Wu <fengguang.wu@intel.com>
Signed-off-by: Li Zefan <lizefan@huawei.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

parent cc045e39

kernel/cgroup.c

+3 −0

Original line number	Diff line number	Diff line
		@@ -2348,6 +2348,9 @@ int cgroup_add_cftypes(struct cgroup_subsys ss, struct cftype cfts)
		{
		int ret;

		if (!cfts \|\| cfts[0].name[0] == '\0')
		return 0;

		ret = cgroup_init_cftypes(ss, cfts);
		if (ret)
		return ret;

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