Revision 03049269de433cb5fe2859be9ae4469ceb1163ed authored by Michal Hocko on 25 March 2016, 21:20:33 UTC, committed by Linus Torvalds on 25 March 2016, 23:37:42 UTC
wake_oom_reaper has allowed only 1 oom victim to be queued. The main
reason for that was the simplicity as other solutions would require some
way of queuing. The current approach is racy and that was deemed
sufficient as the oom_reaper is considered a best effort approach to
help with oom handling when the OOM victim cannot terminate in a
reasonable time. The race could lead to missing an oom victim which can
get stuck
out_of_memory
wake_oom_reaper
cmpxchg // OK
oom_reaper
oom_reap_task
__oom_reap_task
oom_victim terminates
atomic_inc_not_zero // fail
out_of_memory
wake_oom_reaper
cmpxchg // fails
task_to_reap = NULL
This race requires 2 OOM invocations in a short time period which is not
very likely but certainly not impossible. E.g. the original victim
might have not released a lot of memory for some reason.
The situation would improve considerably if wake_oom_reaper used a more
robust queuing. This is what this patch implements. This means adding
oom_reaper_list list_head into task_struct (eat a hole before embeded
thread_struct for that purpose) and a oom_reaper_lock spinlock for
queuing synchronization. wake_oom_reaper will then add the task on the
queue and oom_reaper will dequeue it.
Signed-off-by: Michal Hocko <mhocko@suse.com>
Cc: Vladimir Davydov <vdavydov@virtuozzo.com>
Cc: Andrea Argangeli <andrea@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
1 parent bc448e8
rsa_helper.c
/*
* RSA key extract helper
*
* Copyright (c) 2015, Intel Corporation
* Authors: Tadeusz Struk <tadeusz.struk@intel.com>
*
* This program is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License as published by the Free
* Software Foundation; either version 2 of the License, or (at your option)
* any later version.
*
*/
#include <linux/kernel.h>
#include <linux/export.h>
#include <linux/err.h>
#include <linux/fips.h>
#include <crypto/internal/rsa.h>
#include "rsapubkey-asn1.h"
#include "rsaprivkey-asn1.h"
int rsa_get_n(void *context, size_t hdrlen, unsigned char tag,
const void *value, size_t vlen)
{
struct rsa_key *key = context;
key->n = mpi_read_raw_data(value, vlen);
if (!key->n)
return -ENOMEM;
/* In FIPS mode only allow key size 2K & 3K */
if (fips_enabled && (mpi_get_size(key->n) != 256 &&
mpi_get_size(key->n) != 384)) {
pr_err("RSA: key size not allowed in FIPS mode\n");
mpi_free(key->n);
key->n = NULL;
return -EINVAL;
}
return 0;
}
int rsa_get_e(void *context, size_t hdrlen, unsigned char tag,
const void *value, size_t vlen)
{
struct rsa_key *key = context;
key->e = mpi_read_raw_data(value, vlen);
if (!key->e)
return -ENOMEM;
return 0;
}
int rsa_get_d(void *context, size_t hdrlen, unsigned char tag,
const void *value, size_t vlen)
{
struct rsa_key *key = context;
key->d = mpi_read_raw_data(value, vlen);
if (!key->d)
return -ENOMEM;
/* In FIPS mode only allow key size 2K & 3K */
if (fips_enabled && (mpi_get_size(key->d) != 256 &&
mpi_get_size(key->d) != 384)) {
pr_err("RSA: key size not allowed in FIPS mode\n");
mpi_free(key->d);
key->d = NULL;
return -EINVAL;
}
return 0;
}
static void free_mpis(struct rsa_key *key)
{
mpi_free(key->n);
mpi_free(key->e);
mpi_free(key->d);
key->n = NULL;
key->e = NULL;
key->d = NULL;
}
/**
* rsa_free_key() - frees rsa key allocated by rsa_parse_key()
*
* @rsa_key: struct rsa_key key representation
*/
void rsa_free_key(struct rsa_key *key)
{
free_mpis(key);
}
EXPORT_SYMBOL_GPL(rsa_free_key);
/**
* rsa_parse_pub_key() - extracts an rsa public key from BER encoded buffer
* and stores it in the provided struct rsa_key
*
* @rsa_key: struct rsa_key key representation
* @key: key in BER format
* @key_len: length of key
*
* Return: 0 on success or error code in case of error
*/
int rsa_parse_pub_key(struct rsa_key *rsa_key, const void *key,
unsigned int key_len)
{
int ret;
free_mpis(rsa_key);
ret = asn1_ber_decoder(&rsapubkey_decoder, rsa_key, key, key_len);
if (ret < 0)
goto error;
return 0;
error:
free_mpis(rsa_key);
return ret;
}
EXPORT_SYMBOL_GPL(rsa_parse_pub_key);
/**
* rsa_parse_pub_key() - extracts an rsa private key from BER encoded buffer
* and stores it in the provided struct rsa_key
*
* @rsa_key: struct rsa_key key representation
* @key: key in BER format
* @key_len: length of key
*
* Return: 0 on success or error code in case of error
*/
int rsa_parse_priv_key(struct rsa_key *rsa_key, const void *key,
unsigned int key_len)
{
int ret;
free_mpis(rsa_key);
ret = asn1_ber_decoder(&rsaprivkey_decoder, rsa_key, key, key_len);
if (ret < 0)
goto error;
return 0;
error:
free_mpis(rsa_key);
return ret;
}
EXPORT_SYMBOL_GPL(rsa_parse_priv_key);
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