* [PATCH] cgroup: add a validation check to cgroup_add_cftyps()
@ 2014-02-17 2:41 Li Zefan
2014-02-18 23:20 ` Tejun Heo
0 siblings, 1 reply; 2+ messages in thread
From: Li Zefan @ 2014-02-17 2:41 UTC (permalink / raw)
To: Tejun Heo; +Cc: Fengguang Wu, LKML, Cgroups
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 de00ffa56ea3132c6013fc8f07133b8a1014cf53
("cgroup: make cgroup_subsys->base_cftypes use cgroup_add_cftypes()").
Reported-by: Fengguang Wu <fengguang.wu-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
Signed-off-by: Li Zefan <lizefan-hv44wF8Li93QT0dZR+AlfA@public.gmane.org>
---
kernel/cgroup.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index eaffc08..465c1d8 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -2356,6 +2356,9 @@ 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;
--
1.8.0.2
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH] cgroup: add a validation check to cgroup_add_cftyps()
2014-02-17 2:41 [PATCH] cgroup: add a validation check to cgroup_add_cftyps() Li Zefan
@ 2014-02-18 23:20 ` Tejun Heo
0 siblings, 0 replies; 2+ messages in thread
From: Tejun Heo @ 2014-02-18 23:20 UTC (permalink / raw)
To: Li Zefan; +Cc: Fengguang Wu, LKML, Cgroups
On Mon, Feb 17, 2014 at 10:41:50AM +0800, Li Zefan wrote:
> 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 de00ffa56ea3132c6013fc8f07133b8a1014cf53
> ("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>
Applied to cgroup/for-3.15. Thanks.
--
tejun
^ permalink raw reply [flat|nested] 2+ messages in thread
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