KASAN: null-ptr-deref Read in reclaim_high

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit:    6cab33afc3dd Add linux-next specific files for 20190110
git tree:       linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=178b287b400000
kernel config:  https://syzkaller.appspot.com/x/.config?x=611f89e5b6868db
dashboard link: https://syzkaller.appspot.com/bug?extid=fa11f9da42b46cea3b4a
compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=14259017400000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=141630a0c00000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+fa11f9da42b46cea3b4a@xxxxxxxxxxxxxxxxxxxxxxxxx

==================================================================
BUG: KASAN: null-ptr-deref in atomic64_read  
include/generated/atomic-instrumented.h:836 [inline]
BUG: KASAN: null-ptr-deref in atomic_long_read  
include/generated/atomic-long.h:28 [inline]
BUG: KASAN: null-ptr-deref in page_counter_read  
include/linux/page_counter.h:47 [inline]
BUG: KASAN: null-ptr-deref in reclaim_high.constprop.0+0xa6/0x1e0  
mm/memcontrol.c:2149
Read of size 8 at addr 0000000000000138 by task syz-executor037/7964

CPU: 1 PID: 7964 Comm: syz-executor037 Not tainted 5.0.0-rc1-next-20190110  
#9
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x1db/0x2d0 lib/dump_stack.c:113
 kasan_report.cold+0x5/0x40 mm/kasan/report.c:321
 check_memory_region_inline mm/kasan/generic.c:185 [inline]
 check_memory_region+0x123/0x190 mm/kasan/generic.c:191
 kasan_check_read+0x11/0x20 mm/kasan/common.c:100
 atomic64_read include/generated/atomic-instrumented.h:836 [inline]
 atomic_long_read include/generated/atomic-long.h:28 [inline]
 page_counter_read include/linux/page_counter.h:47 [inline]
 reclaim_high.constprop.0+0xa6/0x1e0 mm/memcontrol.c:2149
 mem_cgroup_handle_over_high+0xc1/0x180 mm/memcontrol.c:2178
 tracehook_notify_resume include/linux/tracehook.h:190 [inline]
 exit_to_usermode_loop+0x299/0x3b0 arch/x86/entry/common.c:166
 prepare_exit_to_usermode arch/x86/entry/common.c:197 [inline]
 syscall_return_slowpath+0x519/0x5f0 arch/x86/entry/common.c:268
 ret_from_fork+0x15/0x50 arch/x86/entry/entry_64.S:344
RIP: 0033:0x44034a
Code: Bad RIP value.
RSP: 002b:00007ffc31cd3040 EFLAGS: 00000246 ORIG_RAX: 0000000000000038
RAX: 0000000000000000 RBX: 0000000000000000 RCX: 000000000044034a
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000001200011
RBP: 00007ffc31cd3060 R08: 0000000000000001 R09: 0000000002027880
R10: 0000000002027b50 R11: 0000000000000246 R12: 0000000000000001
R13: 000000000000cc59 R14: 0000000000000000 R15: 0000000000000000
==================================================================


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