Re: [PATCH -next] mm/vmpressure: fix data-race with memcg->socket_pressure

[Muchun Song]

On Mon, Oct 25, 2021 at 4:14 PM Yuanzheng Song <songyuanzheng@xxxxxxxxxx> wrote:
>
> BUG: KCSAN: data-race in __sk_mem_reduce_allocated / vmpressure
>
> write to 0xffff8881286f4938 of 8 bytes by task 24550 on cpu 3:
>  vmpressure+0x218/0x230 mm/vmpressure.c:307
>  shrink_node_memcgs+0x2b9/0x410 mm/vmscan.c:2658
>  shrink_node+0x9d2/0x11d0 mm/vmscan.c:2769
>  shrink_zones+0x29f/0x470 mm/vmscan.c:2972
>  do_try_to_free_pages+0x193/0x6e0 mm/vmscan.c:3027
>  try_to_free_mem_cgroup_pages+0x1c0/0x3f0 mm/vmscan.c:3345
>  reclaim_high mm/memcontrol.c:2440 [inline]
>  mem_cgroup_handle_over_high+0x18b/0x4d0 mm/memcontrol.c:2624
>  tracehook_notify_resume include/linux/tracehook.h:197 [inline]
>  exit_to_user_mode_loop kernel/entry/common.c:164 [inline]
>  exit_to_user_mode_prepare+0x110/0x170 kernel/entry/common.c:191
>  syscall_exit_to_user_mode+0x16/0x30 kernel/entry/common.c:266
>  ret_from_fork+0x15/0x30 arch/x86/entry/entry_64.S:289
>
> read to 0xffff8881286f4938 of 8 bytes by interrupt on cpu 1:
>  mem_cgroup_under_socket_pressure include/linux/memcontrol.h:1483 [inline]
>  sk_under_memory_pressure include/net/sock.h:1314 [inline]
>  __sk_mem_reduce_allocated+0x1d2/0x270 net/core/sock.c:2696
>  __sk_mem_reclaim+0x44/0x50 net/core/sock.c:2711
>  sk_mem_reclaim include/net/sock.h:1490 [inline]
>  ......
>  net_rx_action+0x17a/0x480 net/core/dev.c:6864
>  __do_softirq+0x12c/0x2af kernel/softirq.c:298
>  run_ksoftirqd+0x13/0x20 kernel/softirq.c:653
>  smpboot_thread_fn+0x33f/0x510 kernel/smpboot.c:165
>  kthread+0x1fc/0x220 kernel/kthread.c:292
>  ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:296
>
> When reading memcg->socket_pressure in mem_cgroup_under_socket_pressure()
> and writing memcg->socket_pressure in vmpressure() at the same time,
> the data-race occurs.
>
> So fix it by using READ_ONCE() and WRITE_ONCE() to read and write
> memcg->socket_pressure.
>
> Signed-off-by: Yuanzheng Song <songyuanzheng@xxxxxxxxxx>

Reviewed-by: Muchun Song <songmuchun@xxxxxxxxxxxxx>

Thanks.