[patch 157/262] mm/vmpressure: fix data-race with memcg->socket_pressure

Andrew Morton
2021-11-05T20:42:55Z

From: Yuanzheng Song <songyuanzheng@huawei.com>
Subject: mm/vmpressure: fix data-race with memcg->socket_pressure

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.

Link: https://lkml.kernel.org/r/20211025082843.671690-1-songyuanzheng@huawei.com
Signed-off-by: Yuanzheng Song <songyuanzheng@huawei.com>
Reviewed-by: Muchun Song <songmuchun@bytedance.com>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Roman Gushchin <guro@fb.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Alex Shi <alexs@kernel.org>
Cc: Wei Yang <richard.weiyang@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

include/linux/memcontrol.h | 2 +-
mm/vmpressure.c | 2 +-
2 files changed, 2 insertions(+), 2 deletions(-)

--- a/include/linux/memcontrol.h~mm-vmpressure-fix-data-race-with-memcg-socket_pressure
+++ a/include/linux/memcontrol.h
@@ -1606,7 +1606,7 @@ static inline bool mem_cgroup_under_sock
if (!cgroup_subsys_on_dfl(memory_cgrp_subsys) && memcg->tcpmem_pressure)
return true;
do {
- if (time_before(jiffies, memcg->socket_pressure))
+ if (time_before(jiffies, READ_ONCE(memcg->socket_pressure)))
return true;
} while ((memcg = parent_mem_cgroup(memcg)));
return false;
--- a/mm/vmpressure.c~mm-vmpressure-fix-data-race-with-memcg-socket_pressure
+++ a/mm/vmpressure.c
@@ -308,7 +308,7 @@ void vmpressure(gfp_t gfp, struct mem_cg
* asserted for a second in which subsequent
* pressure events can occur.
*/
- memcg->socket_pressure = jiffies + HZ;
+ WRITE_ONCE(memcg->socket_pressure, jiffies + HZ);
}
}
}
_