3.6-stable review patch. If anyone has any objections, please let me know.
------------------
From: Mike Galbraith <efa...@gmx.de>
commit fd8ef11730f1d03d5d6555aa53126e9e34f52f12 upstream.
This reverts commit 800d4d30c8f20bd728e5741a3b77c4859a613f7c.
Between commits 8323f26ce342 ("sched: Fix race in task_group()") and
800d4d30c8f2 ("sched, autogroup: Stop going ahead if autogroup is
disabled"), autogroup is a wreck.
With both applied, all you have to do to crash a box is disable
autogroup during boot up, then reboot.. boom, NULL pointer dereference
due to commit 800d4d30c8f2 not allowing autogroup to move things, and
commit 8323f26ce342 making that the only way to switch runqueues:
BUG: unable to handle kernel NULL pointer dereference at (null)
IP: [<ffffffff81063ac0>] effective_load.isra.43+0x50/0x90
Pid: 7047, comm: systemd-user-se Not tainted 3.6.8-smp #7 MEDIONPC
MS-7502/MS-7502
RIP: effective_load.isra.43+0x50/0x90
Process systemd-user-se (pid: 7047, threadinfo ffff880221dde000, task
ffff88022618b3a0)
Call Trace:
select_task_rq_fair+0x255/0x780
try_to_wake_up+0x156/0x2c0
wake_up_state+0xb/0x10
signal_wake_up+0x28/0x40
complete_signal+0x1d6/0x250
__send_signal+0x170/0x310
send_signal+0x40/0x80
do_send_sig_info+0x47/0x90
group_send_sig_info+0x4a/0x70
kill_pid_info+0x3a/0x60
sys_kill+0x97/0x1a0
? vfs_read+0x120/0x160
? sys_read+0x45/0x90
system_call_fastpath+0x16/0x1b
Code: 49 0f af 41 50 31 d2 49 f7 f0 48 83 f8 01 48 0f 46 c6 48 2b 07 48 8b bf
40 01 00 00 48 85 ff 74 3a 45 31 c0 48 8b 8f 50 01 00 00 <48> 8b 11 4c 8b 89 80
00 00 00 49 89 d2 48 01 d0 45 8b 59 58 4c
RIP [<ffffffff81063ac0>] effective_load.isra.43+0x50/0x90
RSP <ffff880221ddfbd8>
CR2: 0000000000000000
Signed-off-by: Mike Galbraith <efa...@gmx.de>
Acked-by: Ingo Molnar <mi...@kernel.org>
Cc: Yong Zhang <yong.zha...@gmail.com>
Cc: Peter Zijlstra <a.p.zijls...@chello.nl>
Signed-off-by: Linus Torvalds <torva...@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>
---
kernel/sched/auto_group.c | 4 ----
kernel/sched/auto_group.h | 5 -----
2 files changed, 9 deletions(-)
--- a/kernel/sched/auto_group.c
+++ b/kernel/sched/auto_group.c
@@ -143,15 +143,11 @@ autogroup_move_group(struct task_struct
p->signal->autogroup = autogroup_kref_get(ag);
- if (!ACCESS_ONCE(sysctl_sched_autogroup_enabled))
- goto out;
-
t = p;
do {
sched_move_task(t);
} while_each_thread(p, t);
-out:
unlock_task_sighand(p, &flags);
autogroup_kref_put(prev);
}
--- a/kernel/sched/auto_group.h
+++ b/kernel/sched/auto_group.h
@@ -4,11 +4,6 @@
#include <linux/rwsem.h>
struct autogroup {
- /*
- * reference doesn't mean how many thread attach to this
- * autogroup now. It just stands for the number of task
- * could use this autogroup.
- */
struct kref kref;
struct task_group *tg;
struct rw_semaphore lock;
--
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