From 17c56de6a8c9970f56375c13f8654bbcbc94c090 Mon Sep 17 00:00:00 2001 From: Yue Zhao Date: Mon, 6 Mar 2023 23:41:37 +0800 Subject: mm, memcg: Prevent memory.oom_control load/store tearing The knob for cgroup v1 memory controller: memory.oom_control is not protected by any locking so it can be modified while it is used. This is not an actual problem because races are unlikely. But it is better to use [READ|WRITE]_ONCE to prevent compiler from doing anything funky. The access of memcg->oom_kill_disable is lockless, so it can be concurrently set at the same time as we are trying to read it. All occurrences of memcg->oom_kill_disable are updated with [READ|WRITE]_ONCE. [findns94@gmail.com: v3] Link: https://lkml.kernel.org/r/20230308162555.14195-4-findns94@gmail.com Link: https://lkml.kernel.org/r/20230306154138.377-4-findns94@gmail.com Signed-off-by: Yue Zhao Acked-by: Shakeel Butt Acked-by: Roman Gushchin Acked-by: Michal Hocko Cc: Johannes Weiner Cc: Matthew Wilcox (Oracle) Cc: Muchun Song Cc: Tang Yizhou Signed-off-by: Andrew Morton --- mm/memcontrol.c | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-) (limited to 'mm/memcontrol.c') diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 1b0112afcad3..5b7062d0f5e0 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -1929,7 +1929,7 @@ static bool mem_cgroup_oom(struct mem_cgroup *memcg, gfp_t mask, int order) * Please note that mem_cgroup_out_of_memory might fail to find a * victim and then we have to bail out from the charge path. */ - if (memcg->oom_kill_disable) { + if (READ_ONCE(memcg->oom_kill_disable)) { if (current->in_user_fault) { css_get(&memcg->css); current->memcg_in_oom = memcg; @@ -1999,7 +1999,7 @@ bool mem_cgroup_oom_synchronize(bool handle) if (locked) mem_cgroup_oom_notify(memcg); - if (locked && !memcg->oom_kill_disable) { + if (locked && !READ_ONCE(memcg->oom_kill_disable)) { mem_cgroup_unmark_under_oom(memcg); finish_wait(&memcg_oom_waitq, &owait.wait); mem_cgroup_out_of_memory(memcg, current->memcg_oom_gfp_mask, @@ -4515,7 +4515,7 @@ static int mem_cgroup_oom_control_read(struct seq_file *sf, void *v) { struct mem_cgroup *memcg = mem_cgroup_from_seq(sf); - seq_printf(sf, "oom_kill_disable %d\n", memcg->oom_kill_disable); + seq_printf(sf, "oom_kill_disable %d\n", READ_ONCE(memcg->oom_kill_disable)); seq_printf(sf, "under_oom %d\n", (bool)memcg->under_oom); seq_printf(sf, "oom_kill %lu\n", atomic_long_read(&memcg->memory_events[MEMCG_OOM_KILL])); @@ -4531,7 +4531,7 @@ static int mem_cgroup_oom_control_write(struct cgroup_subsys_state *css, if (mem_cgroup_is_root(memcg) || !((val == 0) || (val == 1))) return -EINVAL; - memcg->oom_kill_disable = val; + WRITE_ONCE(memcg->oom_kill_disable, val); if (!val) memcg_oom_recover(memcg); @@ -5354,7 +5354,7 @@ mem_cgroup_css_alloc(struct cgroup_subsys_state *parent_css) page_counter_set_high(&memcg->swap, PAGE_COUNTER_MAX); if (parent) { WRITE_ONCE(memcg->swappiness, mem_cgroup_swappiness(parent)); - memcg->oom_kill_disable = parent->oom_kill_disable; + WRITE_ONCE(memcg->oom_kill_disable, READ_ONCE(parent->oom_kill_disable)); page_counter_init(&memcg->memory, &parent->memory); page_counter_init(&memcg->swap, &parent->swap); -- cgit v1.2.3