general protection fault in __mem_cgroup_free

general protection fault in __mem_cgroup_free

[syzbot]

Hello,

syzbot hit the following crash on upstream commit
9dd2326890d89a5179967c947dab2bab34d7ddee (Fri Mar 30 17:29:47 2018 +0000)
Merge tag 'ceph-for-4.16-rc8' of git://github.com/ceph/ceph-client
syzbot dashboard link:  
https://syzkaller.appspot.com/bug?extid=8a5de3cce7cdc70e9ebe

So far this crash happened 14 times on upstream.
C reproducer: https://syzkaller.appspot.com/x/repro.c?id=5578311367393280
syzkaller reproducer:  
https://syzkaller.appspot.com/x/repro.syz?id=5708657048158208
Raw console output:  
https://syzkaller.appspot.com/x/log.txt?id=6693821748346880
Kernel config:  
https://syzkaller.appspot.com/x/.config?id=-2760467897697295172
compiler: gcc (GCC) 7.1.1 20170620

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+8a5de3cce7cdc70e9ebe@syzkaller.appspotmail.com
It will help syzbot understand when the bug is fixed. See footer for  
details.
If you forward the report, please keep this part and the footer.

RBP: 00000000006dcc20 R08: 0000000000000002 R09: 0000000000003335
R10: 0000000000000000 R11: 0000000000000246 R12: 0030656c69662f2e
R13: 00007f1747954d80 R14: ffffffffffffffff R15: 0000000000000006
kasan: CONFIG_KASAN_INLINE enabled
kasan: GPF could be caused by NULL-ptr deref or user memory access
general protection fault: 0000 [#1] SMP KASAN
Dumping ftrace buffer:
    (ftrace buffer empty)
Modules linked in:
CPU: 0 PID: 4422 Comm: syzkaller101598 Not tainted 4.16.0-rc7+ #372
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
RIP: 0010:free_mem_cgroup_per_node_info mm/memcontrol.c:4111 [inline]
RIP: 0010:__mem_cgroup_free+0x71/0x110 mm/memcontrol.c:4120
RSP: 0018:ffff8801accf75a8 EFLAGS: 00010206
RAX: 0000000000000011 RBX: 0000000000000000 RCX: ffffffff8310cdfd
RDX: 0000000000000000 RSI: 0000000000000040 RDI: 0000000000000088
RBP: ffff8801accf75c8 R08: 0000000000000000 R09: ffff8801accf73a0
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: ffff8801ad210d40 R14: dffffc0000000000 R15: ffff8801ad210d40
FS:  00007f1747955700(0000) GS:ffff8801db000000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000460000 CR3: 00000001cb367004 CR4: 00000000001606f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
  mem_cgroup_free mm/memcontrol.c:4128 [inline]
  mem_cgroup_css_alloc+0x403/0x19c0 mm/memcontrol.c:4239
  css_create kernel/cgroup/cgroup.c:4729 [inline]
  cgroup_apply_control_enable+0x44d/0xbc0 kernel/cgroup/cgroup.c:2916
  cgroup_mkdir+0x56f/0xfc0 kernel/cgroup/cgroup.c:4938
  kernfs_iop_mkdir+0x153/0x1e0 fs/kernfs/dir.c:1099
  vfs_mkdir+0x390/0x600 fs/namei.c:3800
  SYSC_mkdirat fs/namei.c:3823 [inline]
  SyS_mkdirat+0x22b/0x2b0 fs/namei.c:3807
  do_syscall_64+0x281/0x940 arch/x86/entry/common.c:287
  entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x44a0c9
RSP: 002b:00007f1747954d78 EFLAGS: 00000246 ORIG_RAX: 0000000000000102
RAX: ffffffffffffffda RBX: 00000000006dcc24 RCX: 000000000044a0c9
RDX: 0000000000000020 RSI: 0000000020000280 RDI: 0000000000000005
RBP: 00000000006dcc20 R08: 0000000000000002 R09: 0000000000003335
R10: 0000000000000000 R11: 0000000000000246 R12: 0030656c69662f2e
R13: 00007f1747954d80 R14: ffffffffffffffff R15: 0000000000000006
Code: 00 00 48 89 f8 48 c1 e8 03 42 80 3c 30 00 0f 85 99 00 00 00 4f 8b a4  
e5 f0 09 00 00 49 8d bc 24 88 00 00 00 48 89 f8 48 c1 e8 03 <42> 80 3c 30  
00 0f 85 88 00 00 00 49 8b bc 24 88 00 00 00 e8 77
RIP: free_mem_cgroup_per_node_info mm/memcontrol.c:4111 [inline] RSP:  
ffff8801accf75a8
RIP: __mem_cgroup_free+0x71/0x110 mm/memcontrol.c:4120 RSP: ffff8801accf75a8
---[ end trace 57ac07c30502ef78 ]---
Kernel panic - not syncing: Fatal exception
Dumping ftrace buffer:
    (ftrace buffer empty)
Kernel Offset: disabled
Rebooting in 86400 seconds..


---
This bug is generated by a dumb bot. It may contain errors.
See https://goo.gl/tpsmEJ for details.
Direct all questions to syzkaller@googlegroups.com.

syzbot will keep track of this bug report.
If you forgot to add the Reported-by tag, once the fix for this bug is  
merged
into any tree, please reply to this email with:
#syz fix: exact-commit-title
If you want to test a patch for this bug, please reply with:
#syz test: git://repo/address.git branch
and provide the patch inline or as an attachment.
To mark this as a duplicate of another syzbot report, please reply with:
#syz dup: exact-subject-of-another-report
If it's a one-off invalid bug report, please reply with:
#syz invalid
Note: if the crash happens again, it will cause creation of a new bug  
report.
Note: all commands must start from beginning of the line in the email body.

Re: general protection fault in __mem_cgroup_free

[Michal Hocko]

[CC Andrey]

On Sat 31-03-18 13:47:05, syzbot wrote:
> Hello,
> 
> syzbot hit the following crash on upstream commit
> 9dd2326890d89a5179967c947dab2bab34d7ddee (Fri Mar 30 17:29:47 2018 +0000)
> Merge tag 'ceph-for-4.16-rc8' of git://github.com/ceph/ceph-client
> syzbot dashboard link:
> https://syzkaller.appspot.com/bug?extid=8a5de3cce7cdc70e9ebe
> 
> So far this crash happened 14 times on upstream.
> C reproducer: https://syzkaller.appspot.com/x/repro.c?id=5578311367393280
> syzkaller reproducer:
> https://syzkaller.appspot.com/x/repro.syz?id=5708657048158208
> Raw console output:
> https://syzkaller.appspot.com/x/log.txt?id=6693821748346880
> Kernel config:
> https://syzkaller.appspot.com/x/.config?id=-2760467897697295172
> compiler: gcc (GCC) 7.1.1 20170620
> 
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+8a5de3cce7cdc70e9ebe@syzkaller.appspotmail.com
> It will help syzbot understand when the bug is fixed. See footer for
> details.
> If you forward the report, please keep this part and the footer.
> 
> RBP: 00000000006dcc20 R08: 0000000000000002 R09: 0000000000003335
> R10: 0000000000000000 R11: 0000000000000246 R12: 0030656c69662f2e
> R13: 00007f1747954d80 R14: ffffffffffffffff R15: 0000000000000006
> kasan: CONFIG_KASAN_INLINE enabled
> kasan: GPF could be caused by NULL-ptr deref or user memory access
> general protection fault: 0000 [#1] SMP KASAN
> Dumping ftrace buffer:
>    (ftrace buffer empty)
> Modules linked in:
> CPU: 0 PID: 4422 Comm: syzkaller101598 Not tainted 4.16.0-rc7+ #372
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
> Google 01/01/2011
> RIP: 0010:free_mem_cgroup_per_node_info mm/memcontrol.c:4111 [inline]
> RIP: 0010:__mem_cgroup_free+0x71/0x110 mm/memcontrol.c:4120

Is this a real bug or a KASAN false positive? The RIP points at
        free_percpu(pn->lruvec_stat_cpu);

Which can be NULL if we are failing to allocate per-node data in
mem_cgroup_alloc. You stack unwinder seems to point to
mem_cgroup_css_alloc->mem_cgroup_free though and that one cannot see
NULL memcg->nodeinfo[node] AFAICS.

Even if this is really mem_cgroup_alloc path then calling free_percpu
with NULL pointer should be OK. Or am I missing something?

> RSP: 0018:ffff8801accf75a8 EFLAGS: 00010206
> RAX: 0000000000000011 RBX: 0000000000000000 RCX: ffffffff8310cdfd
> RDX: 0000000000000000 RSI: 0000000000000040 RDI: 0000000000000088
> RBP: ffff8801accf75c8 R08: 0000000000000000 R09: ffff8801accf73a0
> R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
> R13: ffff8801ad210d40 R14: dffffc0000000000 R15: ffff8801ad210d40
> FS:  00007f1747955700(0000) GS:ffff8801db000000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 0000000000460000 CR3: 00000001cb367004 CR4: 00000000001606f0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> Call Trace:
>  mem_cgroup_free mm/memcontrol.c:4128 [inline]
>  mem_cgroup_css_alloc+0x403/0x19c0 mm/memcontrol.c:4239
>  css_create kernel/cgroup/cgroup.c:4729 [inline]
>  cgroup_apply_control_enable+0x44d/0xbc0 kernel/cgroup/cgroup.c:2916
>  cgroup_mkdir+0x56f/0xfc0 kernel/cgroup/cgroup.c:4938
>  kernfs_iop_mkdir+0x153/0x1e0 fs/kernfs/dir.c:1099
>  vfs_mkdir+0x390/0x600 fs/namei.c:3800
>  SYSC_mkdirat fs/namei.c:3823 [inline]
>  SyS_mkdirat+0x22b/0x2b0 fs/namei.c:3807
>  do_syscall_64+0x281/0x940 arch/x86/entry/common.c:287
>  entry_SYSCALL_64_after_hwframe+0x42/0xb7
> RIP: 0033:0x44a0c9
> RSP: 002b:00007f1747954d78 EFLAGS: 00000246 ORIG_RAX: 0000000000000102
> RAX: ffffffffffffffda RBX: 00000000006dcc24 RCX: 000000000044a0c9
> RDX: 0000000000000020 RSI: 0000000020000280 RDI: 0000000000000005
> RBP: 00000000006dcc20 R08: 0000000000000002 R09: 0000000000003335
> R10: 0000000000000000 R11: 0000000000000246 R12: 0030656c69662f2e
> R13: 00007f1747954d80 R14: ffffffffffffffff R15: 0000000000000006
> Code: 00 00 48 89 f8 48 c1 e8 03 42 80 3c 30 00 0f 85 99 00 00 00 4f 8b a4
> e5 f0 09 00 00 49 8d bc 24 88 00 00 00 48 89 f8 48 c1 e8 03 <42> 80 3c 30 00
> 0f 85 88 00 00 00 49 8b bc 24 88 00 00 00 e8 77
> RIP: free_mem_cgroup_per_node_info mm/memcontrol.c:4111 [inline] RSP:
> ffff8801accf75a8
> RIP: __mem_cgroup_free+0x71/0x110 mm/memcontrol.c:4120 RSP: ffff8801accf75a8
> ---[ end trace 57ac07c30502ef78 ]---
> Kernel panic - not syncing: Fatal exception
-- 
Michal Hocko
SUSE Labs

Re: general protection fault in __mem_cgroup_free

[Michal Hocko]

On Tue 03-04-18 11:37:33, Michal Hocko wrote:
> [CC Andrey]
> 
> On Sat 31-03-18 13:47:05, syzbot wrote:
> > Hello,
> > 
> > syzbot hit the following crash on upstream commit
> > 9dd2326890d89a5179967c947dab2bab34d7ddee (Fri Mar 30 17:29:47 2018 +0000)
> > Merge tag 'ceph-for-4.16-rc8' of git://github.com/ceph/ceph-client
> > syzbot dashboard link:
> > https://syzkaller.appspot.com/bug?extid=8a5de3cce7cdc70e9ebe
> > 
> > So far this crash happened 14 times on upstream.
> > C reproducer: https://syzkaller.appspot.com/x/repro.c?id=5578311367393280
> > syzkaller reproducer:
> > https://syzkaller.appspot.com/x/repro.syz?id=5708657048158208
> > Raw console output:
> > https://syzkaller.appspot.com/x/log.txt?id=6693821748346880
> > Kernel config:
> > https://syzkaller.appspot.com/x/.config?id=-2760467897697295172
> > compiler: gcc (GCC) 7.1.1 20170620
> > 
> > IMPORTANT: if you fix the bug, please add the following tag to the commit:
> > Reported-by: syzbot+8a5de3cce7cdc70e9ebe@syzkaller.appspotmail.com
> > It will help syzbot understand when the bug is fixed. See footer for
> > details.
> > If you forward the report, please keep this part and the footer.
> > 
> > RBP: 00000000006dcc20 R08: 0000000000000002 R09: 0000000000003335
> > R10: 0000000000000000 R11: 0000000000000246 R12: 0030656c69662f2e
> > R13: 00007f1747954d80 R14: ffffffffffffffff R15: 0000000000000006
> > kasan: CONFIG_KASAN_INLINE enabled
> > kasan: GPF could be caused by NULL-ptr deref or user memory access
> > general protection fault: 0000 [#1] SMP KASAN
> > Dumping ftrace buffer:
> >    (ftrace buffer empty)
> > Modules linked in:
> > CPU: 0 PID: 4422 Comm: syzkaller101598 Not tainted 4.16.0-rc7+ #372
> > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
> > Google 01/01/2011
> > RIP: 0010:free_mem_cgroup_per_node_info mm/memcontrol.c:4111 [inline]
> > RIP: 0010:__mem_cgroup_free+0x71/0x110 mm/memcontrol.c:4120
> 
> Is this a real bug or a KASAN false positive? The RIP points at
>         free_percpu(pn->lruvec_stat_cpu);
> 
> Which can be NULL if we are failing to allocate per-node data in
> mem_cgroup_alloc. You stack unwinder seems to point to
> mem_cgroup_css_alloc->mem_cgroup_free though and that one cannot see
> NULL memcg->nodeinfo[node] AFAICS.
> 
> Even if this is really mem_cgroup_alloc path then calling free_percpu
> with NULL pointer should be OK. Or am I missing something?

Scratch that. The bug is real. We can have memcg->nodeinfo[node] =
NULL from mem_cgroup_alloc. It uses the same failure path as the pcp
allocation failure.

This should fix it. I will send the full patch with proper changelog
shortly
---
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index e3d5a0a7917f..0a9c4d5194f3 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -4340,6 +4340,9 @@ static void free_mem_cgroup_per_node_info(struct mem_cgroup *memcg, int node)
 {
 	struct mem_cgroup_per_node *pn = memcg->nodeinfo[node];
 
+	if (!pn)
+		return;
+
 	free_percpu(pn->lruvec_stat_cpu);
 	kfree(pn);
 }
-- 
Michal Hocko
SUSE Labs

Re: general protection fault in __mem_cgroup_free

[Michal Hocko]

Here we go

>From 38f0f08a3f9f19c106ae53350e43dc97e2e3a4d8 Mon Sep 17 00:00:00 2001
From: Michal Hocko <mhocko@suse.com>
Date: Tue, 3 Apr 2018 12:40:41 +0200
Subject: [PATCH] memcg: fix per_node_info cleanup

syzbot has triggered a NULL ptr dereference when allocation fault
injection enforces a failure and alloc_mem_cgroup_per_node_info
initializes memcg->nodeinfo only half way through. __mem_cgroup_free
still tries to free all per-node data and dereferences pn->lruvec_stat_cpu
unconditioanlly even if the specific per-node data hasn't been
initialized.

The bug is quite unlikely to hit because small allocations do not fail
and we would need quite some numa nodes to make struct mem_cgroup_per_node
large enough to cross the costly order.

Reported-by: syzbot+8a5de3cce7cdc70e9ebe@syzkaller.appspotmail.com
Fixes: 00f3ca2c2d66 ("mm: memcontrol: per-lruvec stats infrastructure")
Signed-off-by: Michal Hocko <mhocko@suse.com>
---
 mm/memcontrol.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index e3d5a0a7917f..0a9c4d5194f3 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -4340,6 +4340,9 @@ static void free_mem_cgroup_per_node_info(struct mem_cgroup *memcg, int node)
 {
 	struct mem_cgroup_per_node *pn = memcg->nodeinfo[node];
 
+	if (!pn)
+		return;
+
 	free_percpu(pn->lruvec_stat_cpu);
 	kfree(pn);
 }
-- 
2.16.3

-- 
Michal Hocko
SUSE Labs

Re: general protection fault in __mem_cgroup_free

[Andrey Ryabinin]

On 04/03/2018 01:50 PM, Michal Hocko wrote:
> Here we go
> 
> From 38f0f08a3f9f19c106ae53350e43dc97e2e3a4d8 Mon Sep 17 00:00:00 2001
> From: Michal Hocko <mhocko@suse.com>
> Date: Tue, 3 Apr 2018 12:40:41 +0200
> Subject: [PATCH] memcg: fix per_node_info cleanup
> 
> syzbot has triggered a NULL ptr dereference when allocation fault
> injection enforces a failure and alloc_mem_cgroup_per_node_info
> initializes memcg->nodeinfo only half way through. __mem_cgroup_free
> still tries to free all per-node data and dereferences pn->lruvec_stat_cpu
> unconditioanlly even if the specific per-node data hasn't been
> initialized.
> 
> The bug is quite unlikely to hit because small allocations do not fail
> and we would need quite some numa nodes to make struct mem_cgroup_per_node
> large enough to cross the costly order.
> 
> Reported-by: syzbot+8a5de3cce7cdc70e9ebe@syzkaller.appspotmail.com
> Fixes: 00f3ca2c2d66 ("mm: memcontrol: per-lruvec stats infrastructure")
> Signed-off-by: Michal Hocko <mhocko@suse.com>

Reviewed-by: Andrey Ryabinin <aryabinin@virtuozzo.com>

> ---
>  mm/memcontrol.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index e3d5a0a7917f..0a9c4d5194f3 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -4340,6 +4340,9 @@ static void free_mem_cgroup_per_node_info(struct mem_cgroup *memcg, int node)
>  {
>  	struct mem_cgroup_per_node *pn = memcg->nodeinfo[node];
>  
> +	if (!pn)
> +		return;
> +
>  	free_percpu(pn->lruvec_stat_cpu);
>  	kfree(pn);
>  }
> 

general protection fault in __mem_cgroup_free

[syzbot]

Hello,

syzbot hit the following crash on upstream commit
9dd2326890d89a5179967c947dab2bab34d7ddee (Fri Mar 30 17:29:47 2018 +0000)
Merge tag 'ceph-for-4.16-rc8' of git://github.com/ceph/ceph-client
syzbot dashboard link:  
https://syzkaller.appspot.com/bug?extid=8a5de3cce7cdc70e9ebe

So far this crash happened 14 times on upstream.
C reproducer: https://syzkaller.appspot.com/x/repro.c?id=5578311367393280
syzkaller reproducer:  
https://syzkaller.appspot.com/x/repro.syz?id=5708657048158208
Raw console output:  
https://syzkaller.appspot.com/x/log.txt?id=6693821748346880
Kernel config:  
https://syzkaller.appspot.com/x/.config?id=-2760467897697295172
compiler: gcc (GCC) 7.1.1 20170620

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+8a5de3cce7cdc70e9ebe@syzkaller.appspotmail.com
It will help syzbot understand when the bug is fixed. See footer for  
details.
If you forward the report, please keep this part and the footer.

RBP: 00000000006dcc20 R08: 0000000000000002 R09: 0000000000003335
R10: 0000000000000000 R11: 0000000000000246 R12: 0030656c69662f2e
R13: 00007f1747954d80 R14: ffffffffffffffff R15: 0000000000000006
kasan: CONFIG_KASAN_INLINE enabled
kasan: GPF could be caused by NULL-ptr deref or user memory access
general protection fault: 0000 [#1] SMP KASAN
Dumping ftrace buffer:
    (ftrace buffer empty)
Modules linked in:
CPU: 0 PID: 4422 Comm: syzkaller101598 Not tainted 4.16.0-rc7+ #372
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
RIP: 0010:free_mem_cgroup_per_node_info mm/memcontrol.c:4111 [inline]
RIP: 0010:__mem_cgroup_free+0x71/0x110 mm/memcontrol.c:4120
RSP: 0018:ffff8801accf75a8 EFLAGS: 00010206
RAX: 0000000000000011 RBX: 0000000000000000 RCX: ffffffff8310cdfd
RDX: 0000000000000000 RSI: 0000000000000040 RDI: 0000000000000088
RBP: ffff8801accf75c8 R08: 0000000000000000 R09: ffff8801accf73a0
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: ffff8801ad210d40 R14: dffffc0000000000 R15: ffff8801ad210d40
FS:  00007f1747955700(0000) GS:ffff8801db000000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000460000 CR3: 00000001cb367004 CR4: 00000000001606f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
  mem_cgroup_free mm/memcontrol.c:4128 [inline]
  mem_cgroup_css_alloc+0x403/0x19c0 mm/memcontrol.c:4239
  css_create kernel/cgroup/cgroup.c:4729 [inline]
  cgroup_apply_control_enable+0x44d/0xbc0 kernel/cgroup/cgroup.c:2916
  cgroup_mkdir+0x56f/0xfc0 kernel/cgroup/cgroup.c:4938
  kernfs_iop_mkdir+0x153/0x1e0 fs/kernfs/dir.c:1099
  vfs_mkdir+0x390/0x600 fs/namei.c:3800
  SYSC_mkdirat fs/namei.c:3823 [inline]
  SyS_mkdirat+0x22b/0x2b0 fs/namei.c:3807
  do_syscall_64+0x281/0x940 arch/x86/entry/common.c:287
  entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x44a0c9
RSP: 002b:00007f1747954d78 EFLAGS: 00000246 ORIG_RAX: 0000000000000102
RAX: ffffffffffffffda RBX: 00000000006dcc24 RCX: 000000000044a0c9
RDX: 0000000000000020 RSI: 0000000020000280 RDI: 0000000000000005
RBP: 00000000006dcc20 R08: 0000000000000002 R09: 0000000000003335
R10: 0000000000000000 R11: 0000000000000246 R12: 0030656c69662f2e
R13: 00007f1747954d80 R14: ffffffffffffffff R15: 0000000000000006
Code: 00 00 48 89 f8 48 c1 e8 03 42 80 3c 30 00 0f 85 99 00 00 00 4f 8b a4  
e5 f0 09 00 00 49 8d bc 24 88 00 00 00 48 89 f8 48 c1 e8 03 <42> 80 3c 30  
00 0f 85 88 00 00 00 49 8b bc 24 88 00 00 00 e8 77
RIP: free_mem_cgroup_per_node_info mm/memcontrol.c:4111 [inline] RSP:  
ffff8801accf75a8
RIP: __mem_cgroup_free+0x71/0x110 mm/memcontrol.c:4120 RSP: ffff8801accf75a8
---[ end trace 57ac07c30502ef78 ]---
Kernel panic - not syncing: Fatal exception
Dumping ftrace buffer:
    (ftrace buffer empty)
Kernel Offset: disabled
Rebooting in 86400 seconds..


---
This bug is generated by a dumb bot. It may contain errors.
See https://goo.gl/tpsmEJ for details.
Direct all questions to syzkaller@googlegroups.com.

syzbot will keep track of this bug report.
If you forgot to add the Reported-by tag, once the fix for this bug is  
merged
into any tree, please reply to this email with:
#syz fix: exact-commit-title
If you want to test a patch for this bug, please reply with:
#syz test: git://repo/address.git branch
and provide the patch inline or as an attachment.
To mark this as a duplicate of another syzbot report, please reply with:
#syz dup: exact-subject-of-another-report
If it's a one-off invalid bug report, please reply with:
#syz invalid
Note: if the crash happens again, it will cause creation of a new bug  
report.
Note: all commands must start from beginning of the line in the email body.