KCSAN: data-race in mem_cgroup_select_victim_node / mem_cgroup_select_victim_node

KCSAN: data-race in mem_cgroup_select_victim_node / mem_cgroup_select_victim_node

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit:    05f22368 x86, kcsan: Enable KCSAN for x86
git tree:       https://github.com/google/ktsan.git kcsan
console output: https://syzkaller.appspot.com/x/log.txt?x=1774c6c0e00000
kernel config:  https://syzkaller.appspot.com/x/.config?x=87d111955f40591f
dashboard link: https://syzkaller.appspot.com/bug?extid=234d50ad314ef67bcd16
compiler:       gcc (GCC) 9.0.0 20181231 (experimental)

Unfortunately, I don't have any reproducer for this crash yet.

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+234d50ad314ef67bcd16@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in mem_cgroup_select_victim_node /  
mem_cgroup_select_victim_node

write to 0xffff88809fade9b0 of 4 bytes by task 8603 on cpu 0:
  mem_cgroup_select_victim_node+0xb5/0x3d0 mm/memcontrol.c:1686
  try_to_free_mem_cgroup_pages+0x175/0x4c0 mm/vmscan.c:3376
  reclaim_high.constprop.0+0xf7/0x140 mm/memcontrol.c:2349
  mem_cgroup_handle_over_high+0x96/0x180 mm/memcontrol.c:2430
  tracehook_notify_resume include/linux/tracehook.h:197 [inline]
  exit_to_usermode_loop+0x20c/0x2c0 arch/x86/entry/common.c:163
  prepare_exit_to_usermode+0x180/0x1a0 arch/x86/entry/common.c:194
  swapgs_restore_regs_and_return_to_usermode+0x0/0x40

read to 0xffff88809fade9b0 of 4 bytes by task 7290 on cpu 1:
  mem_cgroup_select_victim_node+0x92/0x3d0 mm/memcontrol.c:1675
  try_to_free_mem_cgroup_pages+0x175/0x4c0 mm/vmscan.c:3376
  reclaim_high.constprop.0+0xf7/0x140 mm/memcontrol.c:2349
  mem_cgroup_handle_over_high+0x96/0x180 mm/memcontrol.c:2430
  tracehook_notify_resume include/linux/tracehook.h:197 [inline]
  exit_to_usermode_loop+0x20c/0x2c0 arch/x86/entry/common.c:163
  prepare_exit_to_usermode+0x180/0x1a0 arch/x86/entry/common.c:194
  swapgs_restore_regs_and_return_to_usermode+0x0/0x40

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 7290 Comm: syz-executor.1 Not tainted 5.4.0-rc3+ #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
==================================================================
Kernel panic - not syncing: panic_on_warn set ...
CPU: 1 PID: 7290 Comm: syz-executor.1 Not tainted 5.4.0-rc3+ #0
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+0xf5/0x159 lib/dump_stack.c:113
  panic+0x210/0x640 kernel/panic.c:221
  kcsan_report.cold+0xc/0x10 kernel/kcsan/report.c:302
  __kcsan_setup_watchpoint+0x32e/0x4a0 kernel/kcsan/core.c:411
  __tsan_read4 kernel/kcsan/kcsan.c:35 [inline]
  __tsan_read4+0x2c/0x30 kernel/kcsan/kcsan.c:35
  mem_cgroup_select_victim_node+0x92/0x3d0 mm/memcontrol.c:1675
  try_to_free_mem_cgroup_pages+0x175/0x4c0 mm/vmscan.c:3376
  reclaim_high.constprop.0+0xf7/0x140 mm/memcontrol.c:2349
  mem_cgroup_handle_over_high+0x96/0x180 mm/memcontrol.c:2430
  tracehook_notify_resume include/linux/tracehook.h:197 [inline]
  exit_to_usermode_loop+0x20c/0x2c0 arch/x86/entry/common.c:163
  prepare_exit_to_usermode+0x180/0x1a0 arch/x86/entry/common.c:194
  retint_user+0x8/0x8
RIP: 0033:0x45862a
Code: 48 85 db 74 b6 41 bc ca 00 00 00 eb 0c 0f 1f 00 48 8b 5b 08 48 85 db  
74 a2 48 8b 3b 48 8b 47 10 48 85 c0 74 05 ff d0 48 8b 3b <f0> ff 4f 28 0f  
94 c0 84 c0 74 db 8b 47 2c 85 c0 74 d4 45 31 d2 ba
RSP: 002b:00007ffec3569600 EFLAGS: 00010246
RAX: 0000000000000000 RBX: 00007ffec3569600 RCX: 00000000004584ca
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000a76d48
RBP: 00007ffec3569640 R08: 0000000000000001 R09: 000000000269f940
R10: 000000000269fc10 R11: 0000000000000246 R12: 00000000000000ca
R13: 0000000000000079 R14: 0000000000000000 R15: 00007ffec3569690
Kernel Offset: disabled
Rebooting in 86400 seconds..


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