From 0b45276928b50e65232016e419e6182eac85d8b2 Mon Sep 17 00:00:00 2001 From: Jiri Slaby Date: Fri, 31 May 2019 22:30:26 -0700 Subject: [PATCH] memcg: make it work on sparse non-0-node systems commit 3e8589963773a5c23e2f1fe4bcad0e9a90b7f471 upstream. We have a single node system with node 0 disabled: Scanning NUMA topology in Northbridge 24 Number of physical nodes 2 Skipping disabled node 0 Node 1 MemBase 0000000000000000 Limit 00000000fbff0000 NODE_DATA(1) allocated [mem 0xfbfda000-0xfbfeffff] This causes crashes in memcg when system boots: BUG: unable to handle kernel NULL pointer dereference at 0000000000000008 #PF error: [normal kernel read fault] ... RIP: 0010:list_lru_add+0x94/0x170 ... Call Trace: d_lru_add+0x44/0x50 dput.part.34+0xfc/0x110 __fput+0x108/0x230 task_work_run+0x9f/0xc0 exit_to_usermode_loop+0xf5/0x100 It is reproducible as far as 4.12. I did not try older kernels. You have to have a new enough systemd, e.g. 241 (the reason is unknown -- was not investigated). Cannot be reproduced with systemd 234. The system crashes because the size of lru array is never updated in memcg_update_all_list_lrus and the reads are past the zero-sized array, causing dereferences of random memory. The root cause are list_lru_memcg_aware checks in the list_lru code. The test in list_lru_memcg_aware is broken: it assumes node 0 is always present, but it is not true on some systems as can be seen above. So fix this by avoiding checks on node 0. Remember the memcg-awareness by a bool flag in struct list_lru. Link: http://lkml.kernel.org/r/20190522091940.3615-1-jslaby@suse.cz Fixes: 60d3fd32a7a9 ("list_lru: introduce per-memcg lists") Signed-off-by: Jiri Slaby Acked-by: Michal Hocko Suggested-by: Vladimir Davydov Acked-by: Vladimir Davydov Reviewed-by: Shakeel Butt Cc: Johannes Weiner Cc: Raghavendra K T Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- include/linux/list_lru.h | 1 + mm/list_lru.c | 8 +++----- 2 files changed, 4 insertions(+), 5 deletions(-) diff --git a/include/linux/list_lru.h b/include/linux/list_lru.h index fa7fd03cb5f9..f2e966937e39 100644 --- a/include/linux/list_lru.h +++ b/include/linux/list_lru.h @@ -51,6 +51,7 @@ struct list_lru { struct list_lru_node *node; #if defined(CONFIG_MEMCG) && !defined(CONFIG_SLOB) struct list_head list; + bool memcg_aware; #endif }; diff --git a/mm/list_lru.c b/mm/list_lru.c index 7a40fa2be858..db3a77c60201 100644 --- a/mm/list_lru.c +++ b/mm/list_lru.c @@ -42,11 +42,7 @@ static void list_lru_unregister(struct list_lru *lru) #if defined(CONFIG_MEMCG) && !defined(CONFIG_SLOB) static inline bool list_lru_memcg_aware(struct list_lru *lru) { - /* - * This needs node 0 to be always present, even - * in the systems supporting sparse numa ids. - */ - return !!lru->node[0].memcg_lrus; + return lru->memcg_aware; } static inline struct list_lru_one * @@ -389,6 +385,8 @@ static int memcg_init_list_lru(struct list_lru *lru, bool memcg_aware) { int i; + lru->memcg_aware = memcg_aware; + if (!memcg_aware) return 0; -- 2.11.0