From dc5736ed7aaf942caaac0c15af74a018e04ec79d Mon Sep 17 00:00:00 2001 From: Li Zefan Date: Mon, 17 Feb 2014 10:41:50 +0800 Subject: [PATCH] cgroup: add a validation check to cgroup_add_cftyps() Fengguang reported this bug: BUG: unable to handle kernel NULL pointer dereference at 0000003c IP: [] cgroup_cfts_commit+0x27/0x1c1 ... Call Trace: [] ? kmem_cache_alloc_trace+0x33f/0x3b7 [] cgroup_add_cftypes+0x8f/0xca [] cgroup_init+0x6a/0x26a [] start_kernel+0x4d7/0x57a [] 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 de00ffa56ea3132c6013fc8f07133b8a1014cf53 ("cgroup: make cgroup_subsys->base_cftypes use cgroup_add_cftypes()"). Reported-by: Fengguang Wu Signed-off-by: Li Zefan Signed-off-by: Tejun Heo --- kernel/cgroup.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/kernel/cgroup.c b/kernel/cgroup.c index 3fe01102607b..771d1b8aaae9 100644 --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -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; -- 2.11.0