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Revision 88e8ac11d2ea3acc003cf01bb5a38c8aa76c3cfd authored by Charan Teja Reddy on 21 August 2020, 00:42:27 UTC, committed by Linus Torvalds on 21 August 2020, 16:52:53 UTC 
mm, page_alloc: fix core hung in free_pcppages_bulk()
 
The following race is observed with the repeated online, offline and a
delay between two successive online of memory blocks of movable zone.

P1						P2

Online the first memory block in
the movable zone. The pcp struct
values are initialized to default
values,i.e., pcp->high = 0 &
pcp->batch = 1.

					Allocate the pages from the
					movable zone.

Try to Online the second memory
block in the movable zone thus it
entered the online_pages() but yet
to call zone_pcp_update().
					This process is entered into
					the exit path thus it tries
					to release the order-0 pages
					to pcp lists through
					free_unref_page_commit().
					As pcp->high = 0, pcp->count = 1
					proceed to call the function
					free_pcppages_bulk().
Update the pcp values thus the
new pcp values are like, say,
pcp->high = 378, pcp->batch = 63.
					Read the pcp's batch value using
					READ_ONCE() and pass the same to
					free_pcppages_bulk(), pcp values
					passed here are, batch = 63,
					count = 1.

					Since num of pages in the pcp
					lists are less than ->batch,
					then it will stuck in
					while(list_empty(list)) loop
					with interrupts disabled thus
					a core hung.

Avoid this by ensuring free_pcppages_bulk() is called with proper count of
pcp list pages.

The mentioned race is some what easily reproducible without [1] because
pcp's are not updated for the first memory block online and thus there is
a enough race window for P2 between alloc+free and pcp struct values
update through onlining of second memory block.

With [1], the race still exists but it is very narrow as we update the pcp
struct values for the first memory block online itself.

This is not limited to the movable zone, it could also happen in cases
with the normal zone (e.g., hotplug to a node that only has DMA memory, or
no other memory yet).

[1]: https://patchwork.kernel.org/patch/11696389/

Fixes: 5f8dcc21211a ("page-allocator: split per-cpu list into one-list-per-migrate-type")
Signed-off-by: Charan Teja Reddy <charante@codeaurora.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: David Hildenbrand <david@redhat.com>
Acked-by: David Rientjes <rientjes@google.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Vinayak Menon <vinmenon@codeaurora.org>
Cc: <stable@vger.kernel.org> [2.6+]
Link: http://lkml.kernel.org/r/1597150703-19003-1-git-send-email-charante@codeaurora.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
1 parent e08d3fd
Raw File
llsec.h 
/* SPDX-License-Identifier: GPL-2.0-only */
/*
 * Copyright (C) 2014 Fraunhofer ITWM
 *
 * Written by:
 * Phoebe Buckheister <phoebe.buckheister@itwm.fraunhofer.de>
 */

#ifndef MAC802154_LLSEC_H
#define MAC802154_LLSEC_H

#include <linux/slab.h>
#include <linux/hashtable.h>
#include <linux/kref.h>
#include <linux/spinlock.h>
#include <net/af_ieee802154.h>
#include <net/ieee802154_netdev.h>

struct mac802154_llsec_key {
	struct ieee802154_llsec_key key;

	/* one tfm for each authsize (4/8/16) */
	struct crypto_aead *tfm[3];
	struct crypto_sync_skcipher *tfm0;

	struct kref ref;
};

struct mac802154_llsec_device_key {
	struct ieee802154_llsec_device_key devkey;

	struct rcu_head rcu;
};

struct mac802154_llsec_device {
	struct ieee802154_llsec_device dev;

	struct hlist_node bucket_s;
	struct hlist_node bucket_hw;

	/* protects dev.frame_counter and the elements of dev.keys */
	spinlock_t lock;

	struct rcu_head rcu;
};

struct mac802154_llsec_seclevel {
	struct ieee802154_llsec_seclevel level;

	struct rcu_head rcu;
};

struct mac802154_llsec {
	struct ieee802154_llsec_params params;
	struct ieee802154_llsec_table table;

	DECLARE_HASHTABLE(devices_short, 6);
	DECLARE_HASHTABLE(devices_hw, 6);

	/* protects params, all other fields are fine with RCU */
	rwlock_t lock;
};

void mac802154_llsec_init(struct mac802154_llsec *sec);
void mac802154_llsec_destroy(struct mac802154_llsec *sec);

int mac802154_llsec_get_params(struct mac802154_llsec *sec,
			       struct ieee802154_llsec_params *params);
int mac802154_llsec_set_params(struct mac802154_llsec *sec,
			       const struct ieee802154_llsec_params *params,
			       int changed);

int mac802154_llsec_key_add(struct mac802154_llsec *sec,
			    const struct ieee802154_llsec_key_id *id,
			    const struct ieee802154_llsec_key *key);
int mac802154_llsec_key_del(struct mac802154_llsec *sec,
			    const struct ieee802154_llsec_key_id *key);

int mac802154_llsec_dev_add(struct mac802154_llsec *sec,
			    const struct ieee802154_llsec_device *dev);
int mac802154_llsec_dev_del(struct mac802154_llsec *sec,
			    __le64 device_addr);

int mac802154_llsec_devkey_add(struct mac802154_llsec *sec,
			       __le64 dev_addr,
			       const struct ieee802154_llsec_device_key *key);
int mac802154_llsec_devkey_del(struct mac802154_llsec *sec,
			       __le64 dev_addr,
			       const struct ieee802154_llsec_device_key *key);

int mac802154_llsec_seclevel_add(struct mac802154_llsec *sec,
				 const struct ieee802154_llsec_seclevel *sl);
int mac802154_llsec_seclevel_del(struct mac802154_llsec *sec,
				 const struct ieee802154_llsec_seclevel *sl);

int mac802154_llsec_encrypt(struct mac802154_llsec *sec, struct sk_buff *skb);
int mac802154_llsec_decrypt(struct mac802154_llsec *sec, struct sk_buff *skb);

#endif /* MAC802154_LLSEC_H */
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