Re: [patch 2/2] mm: memcontrol: default hierarchy interface for memory

[Sasha Levin]

Hi Johannes,

On 01/20/2015 10:31 AM, Johannes Weiner wrote:
> Introduce the basic control files to account, partition, and limit
> memory using cgroups in default hierarchy mode.

I'm seeing the following while fuzzing:

[ 5634.427361] GPF could be caused by NULL-ptr deref or user memory access
general protection fault: 0000 [#1] SMP KASAN
[ 5634.430492] Dumping ftrace buffer:
[ 5634.430565]    (ftrace buffer empty)
[ 5634.430565] Modules linked in:
[ 5634.430565] CPU: 0 PID: 3983 Comm: kswapd0 Not tainted 3.19.0-next-20150222-sasha-00045-g8dc7569 #1943
[ 5634.430565] task: ffff88056a7cb000 ti: ffff880568860000 task.ti: ffff880568860000
[ 5634.430565] RIP: mem_cgroup_low (./arch/x86/include/asm/atomic64_64.h:21 include/asm-generic/atomic-long.h:31 include/linux/page_counter.h:34 mm/memcontrol.c:5438)
[ 5634.430565] RSP: 0000:ffff880568867968  EFLAGS: 00010202
[ 5634.430565] RAX: 000000000000001a RBX: 0000000000000000 RCX: 0000000000000000
[ 5634.430565] RDX: 1ffff1000822a3a4 RSI: ffff880041151bd8 RDI: ffff880041151cb8
[ 5634.430565] RBP: ffff880568867998 R08: 0000000000000000 R09: 0000000000000001
[ 5634.430565] R10: ffff880041151bd8 R11: 0000000000000000 R12: 00000000000000d0
[ 5634.430565] R13: dffffc0000000000 R14: ffff8800000237b0 R15: 0000000000000000
[ 5634.430565] FS:  0000000000000000(0000) GS:ffff88091aa00000(0000) knlGS:0000000000000000
[ 5634.430565] CS:  0010 DS: 0000 ES: 0000 CR0: 000000008005003b
[ 5634.430565] CR2: 000000000138efd8 CR3: 0000000500078000 CR4: 00000000000007b0
[ 5634.430565] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[ 5634.430565] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000600
[ 5634.430565] Stack:
[ 5634.430565]  ffff880568867988 ffff880041151bd8 0000000000000000 ffff880000610000
[ 5634.430565]  ffff880568867d68 dffffc0000000000 ffff880568867b38 ffffffff81a1ac0f
[ 5634.430565]  ffffffff81b875b0 1ffff100ad10cf45 ffff880568867d80 ffff880568867d70
[ 5634.430565] Call Trace:
[ 5634.430565] shrink_zone (mm/vmscan.c:2389)
[ 5634.430565] ? percpu_ref_get_many (include/linux/percpu-refcount.h:270)
[ 5634.430565] ? shrink_lruvec (mm/vmscan.c:2365)
[ 5634.430565] kswapd (mm/vmscan.c:3104 mm/vmscan.c:3276 mm/vmscan.c:3484)
[ 5634.430565] ? debug_check_no_locks_freed (kernel/locking/lockdep.c:3051)
[ 5634.430565] ? mem_cgroup_shrink_node_zone (mm/vmscan.c:3401)
[ 5634.430565] ? __tick_nohz_task_switch (./arch/x86/include/asm/paravirt.h:809 (discriminator 2) kernel/time/tick-sched.c:292 (discriminator 2))
[ 5634.430565] ? trace_hardirqs_on_caller (kernel/locking/lockdep.c:2554 kernel/locking/lockdep.c:2601)
[ 5634.430565] ? trace_hardirqs_on (kernel/locking/lockdep.c:2609)
[ 5634.430565] ? finish_task_switch (kernel/sched/core.c:2229)
[ 5634.430565] ? finish_task_switch (kernel/sched/sched.h:1058 kernel/sched/core.c:2210)
[ 5634.430565] ? __init_waitqueue_head (kernel/sched/wait.c:292)
[ 5634.430565] ? __schedule (kernel/sched/core.c:2320 kernel/sched/core.c:2778)
[ 5634.430565] ? mem_cgroup_shrink_node_zone (mm/vmscan.c:3401)
[ 5634.430565] ? mem_cgroup_shrink_node_zone (mm/vmscan.c:3401)
[ 5634.430565] kthread (kernel/kthread.c:207)
[ 5634.430565] ? __tick_nohz_task_switch (./arch/x86/include/asm/paravirt.h:809 (discriminator 2) kernel/time/tick-sched.c:292 (discriminator 2))
[ 5634.430565] ? flush_kthread_work (kernel/kthread.c:176)
[ 5634.430565] ? trace_hardirqs_on_caller (kernel/locking/lockdep.c:2554 kernel/locking/lockdep.c:2601)
[ 5634.430565] ? schedule_tail (kernel/sched/core.c:2268)
[ 5634.430565] ? flush_kthread_work (kernel/kthread.c:176)
[ 5634.430565] ret_from_fork (arch/x86/kernel/entry_64.S:283)
[ 5634.430565] ? flush_kthread_work (kernel/kthread.c:176)
[ 5634.430565] Code: ff 49 39 de 0f 84 bd 00 00 00 49 89 dc 49 81 c4 d0 00 00 00 0f 84 f7 00 00 00 41 f6 c4 07 0f 85 ed 00 00 00 4c 89 e0 48 c1 e8 03 <42> 80 3c 28 00 0f 85 ef 00 00 00 4c 8b a3 d0 00 00 00 48 85 db
All code
========
   0:	ff 49 39             	decl   0x39(%rcx)
   3:	de 0f                	fimul  (%rdi)
   5:	84 bd 00 00 00 49    	test   %bh,0x49000000(%rbp)
   b:	89 dc                	mov    %ebx,%esp
   d:	49 81 c4 d0 00 00 00 	add    $0xd0,%r12
  14:	0f 84 f7 00 00 00    	je     0x111
  1a:	41 f6 c4 07          	test   $0x7,%r12b
  1e:	0f 85 ed 00 00 00    	jne    0x111
  24:	4c 89 e0             	mov    %r12,%rax
  27:	48 c1 e8 03          	shr    $0x3,%rax
  2b:*	42 80 3c 28 00       	cmpb   $0x0,(%rax,%r13,1)		<-- trapping instruction
  30:	0f 85 ef 00 00 00    	jne    0x125
  36:	4c 8b a3 d0 00 00 00 	mov    0xd0(%rbx),%r12
  3d:	48 85 db             	test   %rbx,%rbx
	...

Code starting with the faulting instruction
===========================================
   0:	42 80 3c 28 00       	cmpb   $0x0,(%rax,%r13,1)
   5:	0f 85 ef 00 00 00    	jne    0xfa
   b:	4c 8b a3 d0 00 00 00 	mov    0xd0(%rbx),%r12
  12:	48 85 db             	test   %rbx,%rbx
	...
[ 5634.430565] RIP mem_cgroup_low (./arch/x86/include/asm/atomic64_64.h:21 include/asm-generic/atomic-long.h:31 include/linux/page_counter.h:34 mm/memcontrol.c:5438)
[ 5634.430565]  RSP <ffff880568867968>


Thanks,
Sasha
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