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From: Jiri Slaby <jslaby@suse.cz>
To: akpm@linux-foundation.org
Cc: linux-kernel@vger.kernel.org, Jiri Slaby <jslaby@suse.cz>,
	Johannes Weiner <hannes@cmpxchg.org>,
	Michal Hocko <mhocko@suse.com>,
	Vladimir Davydov <vdavydov.dev@gmail.com>,
	Shakeel Butt <shakeelb@google.com>,
	cgroups@vger.kernel.org, stable@vger.kernel.org,
	linux-mm@kvack.org,
	Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com>
Subject: [PATCH -resend v2] memcg: make it work on sparse non-0-node systems
Date: Wed, 22 May 2019 11:19:40 +0200
Message-ID: <20190522091940.3615-1-jslaby@suse.cz> (raw)
In-Reply-To: <20190517114204.6330-1-jslaby@suse.cz>

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.

[v2] use the idea proposed by Vladimir -- the bool flag.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Fixes: 60d3fd32a7a9 ("list_lru: introduce per-memcg lists")
Cc: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Michal Hocko <mhocko@suse.com>
Suggested-by: Vladimir Davydov <vdavydov.dev@gmail.com>
Acked-by: Vladimir Davydov <vdavydov.dev@gmail.com>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Cc: <cgroups@vger.kernel.org>
Cc: <stable@vger.kernel.org>
Cc: <linux-mm@kvack.org>
Cc: Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com>
---

This is only a resent patch. I did not send it the akpm's way previously.

 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 aa5efd9351eb..d5ceb2839a2d 100644
--- a/include/linux/list_lru.h
+++ b/include/linux/list_lru.h
@@ -54,6 +54,7 @@ struct list_lru {
 #ifdef CONFIG_MEMCG_KMEM
 	struct list_head	list;
 	int			shrinker_id;
+	bool			memcg_aware;
 #endif
 };
 
diff --git a/mm/list_lru.c b/mm/list_lru.c
index 0730bf8ff39f..d3b538146efd 100644
--- a/mm/list_lru.c
+++ b/mm/list_lru.c
@@ -37,11 +37,7 @@ static int lru_shrinker_id(struct list_lru *lru)
 
 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 *
@@ -451,6 +447,8 @@ 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;
 
-- 
2.21.0


  parent reply index

Thread overview: 23+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-04-29  8:16 memcg causes crashes in list_lru_add Jiri Slaby
2019-04-29  9:25 ` Jiri Slaby
2019-04-29 10:09   ` Jiri Slaby
2019-04-29 10:40     ` Michal Hocko
2019-04-29 10:43       ` Michal Hocko
2019-04-29 10:59     ` [PATCH] memcg: make it work on sparse non-0-node systems Jiri Slaby
2019-04-29 11:30       ` Michal Hocko
2019-04-29 11:55         ` Jiri Slaby
2019-04-29 12:11           ` Jiri Slaby
2019-04-29 13:15           ` Michal Hocko
2019-05-09  7:21       ` Jiri Slaby
2019-05-09 12:25       ` Vladimir Davydov
2019-05-09 16:05         ` Shakeel Butt
2019-05-16 13:59         ` Michal Hocko
2019-05-17  4:48           ` Jiri Slaby
2019-05-17  8:00             ` Vladimir Davydov
2019-05-17  8:16               ` Jiri Slaby
2019-05-17 11:42               ` [PATCH v2] " Jiri Slaby
2019-05-17 12:13                 ` Shakeel Butt
2019-05-17 12:27                 ` Michal Hocko
2019-05-22  9:19                 ` Jiri Slaby [this message]
2019-05-29 13:14                   ` [PATCH -resend " Sasha Levin
2019-04-29 10:17   ` memcg causes crashes in list_lru_add Michal Hocko

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