Revision 63cae12bce9861cec309798d34701cf3da20bc71 authored by Peter Zijlstra on 09 December 2016, 13:59:00 UTC, committed by Ingo Molnar on 14 January 2017, 09:56:10 UTC
There is problem with installing an event in a task that is 'stuck' on
an offline CPU.
Blocked tasks are not dis-assosciated from offlined CPUs, after all, a
blocked task doesn't run and doesn't require a CPU etc.. Only on
wakeup do we ammend the situation and place the task on a available
CPU.
If we hit such a task with perf_install_in_context() we'll loop until
either that task wakes up or the CPU comes back online, if the task
waking depends on the event being installed, we're stuck.
While looking into this issue, I also spotted another problem, if we
hit a task with perf_install_in_context() that is in the middle of
being migrated, that is we observe the old CPU before sending the IPI,
but run the IPI (on the old CPU) while the task is already running on
the new CPU, things also go sideways.
Rework things to rely on task_curr() -- outside of rq->lock -- which
is rather tricky. Imagine the following scenario where we're trying to
install the first event into our task 't':
CPU0 CPU1 CPU2
(current == t)
t->perf_event_ctxp[] = ctx;
smp_mb();
cpu = task_cpu(t);
switch(t, n);
migrate(t, 2);
switch(p, t);
ctx = t->perf_event_ctxp[]; // must not be NULL
smp_function_call(cpu, ..);
generic_exec_single()
func();
spin_lock(ctx->lock);
if (task_curr(t)) // false
add_event_to_ctx();
spin_unlock(ctx->lock);
perf_event_context_sched_in();
spin_lock(ctx->lock);
// sees event
So its CPU0's store of t->perf_event_ctxp[] that must not go 'missing'.
Because if CPU2's load of that variable were to observe NULL, it would
not try to schedule the ctx and we'd have a task running without its
counter, which would be 'bad'.
As long as we observe !NULL, we'll acquire ctx->lock. If we acquire it
first and not see the event yet, then CPU0 must observe task_curr()
and retry. If the install happens first, then we must see the event on
sched-in and all is well.
I think we can translate the first part (until the 'must not be NULL')
of the scenario to a litmus test like:
C C-peterz
{
}
P0(int *x, int *y)
{
int r1;
WRITE_ONCE(*x, 1);
smp_mb();
r1 = READ_ONCE(*y);
}
P1(int *y, int *z)
{
WRITE_ONCE(*y, 1);
smp_store_release(z, 1);
}
P2(int *x, int *z)
{
int r1;
int r2;
r1 = smp_load_acquire(z);
smp_mb();
r2 = READ_ONCE(*x);
}
exists
(0:r1=0 /\ 2:r1=1 /\ 2:r2=0)
Where:
x is perf_event_ctxp[],
y is our tasks's CPU, and
z is our task being placed on the rq of CPU2.
The P0 smp_mb() is the one added by this patch, ordering the store to
perf_event_ctxp[] from find_get_context() and the load of task_cpu()
in task_function_call().
The smp_store_release/smp_load_acquire model the RCpc locking of the
rq->lock and the smp_mb() of P2 is the context switch switching from
whatever CPU2 was running to our task 't'.
This litmus test evaluates into:
Test C-peterz Allowed
States 7
0:r1=0; 2:r1=0; 2:r2=0;
0:r1=0; 2:r1=0; 2:r2=1;
0:r1=0; 2:r1=1; 2:r2=1;
0:r1=1; 2:r1=0; 2:r2=0;
0:r1=1; 2:r1=0; 2:r2=1;
0:r1=1; 2:r1=1; 2:r2=0;
0:r1=1; 2:r1=1; 2:r2=1;
No
Witnesses
Positive: 0 Negative: 7
Condition exists (0:r1=0 /\ 2:r1=1 /\ 2:r2=0)
Observation C-peterz Never 0 7
Hash=e427f41d9146b2a5445101d3e2fcaa34
And the strong and weak model agree.
Reported-by: Mark Rutland <mark.rutland@arm.com>
Tested-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Cc: Will Deacon <will.deacon@arm.com>
Cc: jeremy.linton@arm.com
Link: http://lkml.kernel.org/r/20161209135900.GU3174@twins.programming.kicks-ass.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
1 parent ad5013d
authenc.c
/*
* Authenc: Simple AEAD wrapper for IPsec
*
* Copyright (c) 2007-2015 Herbert Xu <herbert@gondor.apana.org.au>
*
* 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 <crypto/internal/aead.h>
#include <crypto/internal/hash.h>
#include <crypto/internal/skcipher.h>
#include <crypto/authenc.h>
#include <crypto/null.h>
#include <crypto/scatterwalk.h>
#include <linux/err.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/rtnetlink.h>
#include <linux/slab.h>
#include <linux/spinlock.h>
struct authenc_instance_ctx {
struct crypto_ahash_spawn auth;
struct crypto_skcipher_spawn enc;
unsigned int reqoff;
};
struct crypto_authenc_ctx {
struct crypto_ahash *auth;
struct crypto_skcipher *enc;
struct crypto_skcipher *null;
};
struct authenc_request_ctx {
struct scatterlist src[2];
struct scatterlist dst[2];
char tail[];
};
static void authenc_request_complete(struct aead_request *req, int err)
{
if (err != -EINPROGRESS)
aead_request_complete(req, err);
}
int crypto_authenc_extractkeys(struct crypto_authenc_keys *keys, const u8 *key,
unsigned int keylen)
{
struct rtattr *rta = (struct rtattr *)key;
struct crypto_authenc_key_param *param;
if (!RTA_OK(rta, keylen))
return -EINVAL;
if (rta->rta_type != CRYPTO_AUTHENC_KEYA_PARAM)
return -EINVAL;
if (RTA_PAYLOAD(rta) < sizeof(*param))
return -EINVAL;
param = RTA_DATA(rta);
keys->enckeylen = be32_to_cpu(param->enckeylen);
key += RTA_ALIGN(rta->rta_len);
keylen -= RTA_ALIGN(rta->rta_len);
if (keylen < keys->enckeylen)
return -EINVAL;
keys->authkeylen = keylen - keys->enckeylen;
keys->authkey = key;
keys->enckey = key + keys->authkeylen;
return 0;
}
EXPORT_SYMBOL_GPL(crypto_authenc_extractkeys);
static int crypto_authenc_setkey(struct crypto_aead *authenc, const u8 *key,
unsigned int keylen)
{
struct crypto_authenc_ctx *ctx = crypto_aead_ctx(authenc);
struct crypto_ahash *auth = ctx->auth;
struct crypto_skcipher *enc = ctx->enc;
struct crypto_authenc_keys keys;
int err = -EINVAL;
if (crypto_authenc_extractkeys(&keys, key, keylen) != 0)
goto badkey;
crypto_ahash_clear_flags(auth, CRYPTO_TFM_REQ_MASK);
crypto_ahash_set_flags(auth, crypto_aead_get_flags(authenc) &
CRYPTO_TFM_REQ_MASK);
err = crypto_ahash_setkey(auth, keys.authkey, keys.authkeylen);
crypto_aead_set_flags(authenc, crypto_ahash_get_flags(auth) &
CRYPTO_TFM_RES_MASK);
if (err)
goto out;
crypto_skcipher_clear_flags(enc, CRYPTO_TFM_REQ_MASK);
crypto_skcipher_set_flags(enc, crypto_aead_get_flags(authenc) &
CRYPTO_TFM_REQ_MASK);
err = crypto_skcipher_setkey(enc, keys.enckey, keys.enckeylen);
crypto_aead_set_flags(authenc, crypto_skcipher_get_flags(enc) &
CRYPTO_TFM_RES_MASK);
out:
return err;
badkey:
crypto_aead_set_flags(authenc, CRYPTO_TFM_RES_BAD_KEY_LEN);
goto out;
}
static void authenc_geniv_ahash_done(struct crypto_async_request *areq, int err)
{
struct aead_request *req = areq->data;
struct crypto_aead *authenc = crypto_aead_reqtfm(req);
struct aead_instance *inst = aead_alg_instance(authenc);
struct authenc_instance_ctx *ictx = aead_instance_ctx(inst);
struct authenc_request_ctx *areq_ctx = aead_request_ctx(req);
struct ahash_request *ahreq = (void *)(areq_ctx->tail + ictx->reqoff);
if (err)
goto out;
scatterwalk_map_and_copy(ahreq->result, req->dst,
req->assoclen + req->cryptlen,
crypto_aead_authsize(authenc), 1);
out:
aead_request_complete(req, err);
}
static int crypto_authenc_genicv(struct aead_request *req, unsigned int flags)
{
struct crypto_aead *authenc = crypto_aead_reqtfm(req);
struct aead_instance *inst = aead_alg_instance(authenc);
struct crypto_authenc_ctx *ctx = crypto_aead_ctx(authenc);
struct authenc_instance_ctx *ictx = aead_instance_ctx(inst);
struct crypto_ahash *auth = ctx->auth;
struct authenc_request_ctx *areq_ctx = aead_request_ctx(req);
struct ahash_request *ahreq = (void *)(areq_ctx->tail + ictx->reqoff);
u8 *hash = areq_ctx->tail;
int err;
hash = (u8 *)ALIGN((unsigned long)hash + crypto_ahash_alignmask(auth),
crypto_ahash_alignmask(auth) + 1);
ahash_request_set_tfm(ahreq, auth);
ahash_request_set_crypt(ahreq, req->dst, hash,
req->assoclen + req->cryptlen);
ahash_request_set_callback(ahreq, flags,
authenc_geniv_ahash_done, req);
err = crypto_ahash_digest(ahreq);
if (err)
return err;
scatterwalk_map_and_copy(hash, req->dst, req->assoclen + req->cryptlen,
crypto_aead_authsize(authenc), 1);
return 0;
}
static void crypto_authenc_encrypt_done(struct crypto_async_request *req,
int err)
{
struct aead_request *areq = req->data;
if (err)
goto out;
err = crypto_authenc_genicv(areq, 0);
out:
authenc_request_complete(areq, err);
}
static int crypto_authenc_copy_assoc(struct aead_request *req)
{
struct crypto_aead *authenc = crypto_aead_reqtfm(req);
struct crypto_authenc_ctx *ctx = crypto_aead_ctx(authenc);
SKCIPHER_REQUEST_ON_STACK(skreq, ctx->null);
skcipher_request_set_tfm(skreq, ctx->null);
skcipher_request_set_callback(skreq, aead_request_flags(req),
NULL, NULL);
skcipher_request_set_crypt(skreq, req->src, req->dst, req->assoclen,
NULL);
return crypto_skcipher_encrypt(skreq);
}
static int crypto_authenc_encrypt(struct aead_request *req)
{
struct crypto_aead *authenc = crypto_aead_reqtfm(req);
struct aead_instance *inst = aead_alg_instance(authenc);
struct crypto_authenc_ctx *ctx = crypto_aead_ctx(authenc);
struct authenc_instance_ctx *ictx = aead_instance_ctx(inst);
struct authenc_request_ctx *areq_ctx = aead_request_ctx(req);
struct crypto_skcipher *enc = ctx->enc;
unsigned int cryptlen = req->cryptlen;
struct skcipher_request *skreq = (void *)(areq_ctx->tail +
ictx->reqoff);
struct scatterlist *src, *dst;
int err;
src = scatterwalk_ffwd(areq_ctx->src, req->src, req->assoclen);
dst = src;
if (req->src != req->dst) {
err = crypto_authenc_copy_assoc(req);
if (err)
return err;
dst = scatterwalk_ffwd(areq_ctx->dst, req->dst, req->assoclen);
}
skcipher_request_set_tfm(skreq, enc);
skcipher_request_set_callback(skreq, aead_request_flags(req),
crypto_authenc_encrypt_done, req);
skcipher_request_set_crypt(skreq, src, dst, cryptlen, req->iv);
err = crypto_skcipher_encrypt(skreq);
if (err)
return err;
return crypto_authenc_genicv(req, aead_request_flags(req));
}
static int crypto_authenc_decrypt_tail(struct aead_request *req,
unsigned int flags)
{
struct crypto_aead *authenc = crypto_aead_reqtfm(req);
struct aead_instance *inst = aead_alg_instance(authenc);
struct crypto_authenc_ctx *ctx = crypto_aead_ctx(authenc);
struct authenc_instance_ctx *ictx = aead_instance_ctx(inst);
struct authenc_request_ctx *areq_ctx = aead_request_ctx(req);
struct ahash_request *ahreq = (void *)(areq_ctx->tail + ictx->reqoff);
struct skcipher_request *skreq = (void *)(areq_ctx->tail +
ictx->reqoff);
unsigned int authsize = crypto_aead_authsize(authenc);
u8 *ihash = ahreq->result + authsize;
struct scatterlist *src, *dst;
scatterwalk_map_and_copy(ihash, req->src, ahreq->nbytes, authsize, 0);
if (crypto_memneq(ihash, ahreq->result, authsize))
return -EBADMSG;
src = scatterwalk_ffwd(areq_ctx->src, req->src, req->assoclen);
dst = src;
if (req->src != req->dst)
dst = scatterwalk_ffwd(areq_ctx->dst, req->dst, req->assoclen);
skcipher_request_set_tfm(skreq, ctx->enc);
skcipher_request_set_callback(skreq, aead_request_flags(req),
req->base.complete, req->base.data);
skcipher_request_set_crypt(skreq, src, dst,
req->cryptlen - authsize, req->iv);
return crypto_skcipher_decrypt(skreq);
}
static void authenc_verify_ahash_done(struct crypto_async_request *areq,
int err)
{
struct aead_request *req = areq->data;
if (err)
goto out;
err = crypto_authenc_decrypt_tail(req, 0);
out:
authenc_request_complete(req, err);
}
static int crypto_authenc_decrypt(struct aead_request *req)
{
struct crypto_aead *authenc = crypto_aead_reqtfm(req);
unsigned int authsize = crypto_aead_authsize(authenc);
struct aead_instance *inst = aead_alg_instance(authenc);
struct crypto_authenc_ctx *ctx = crypto_aead_ctx(authenc);
struct authenc_instance_ctx *ictx = aead_instance_ctx(inst);
struct crypto_ahash *auth = ctx->auth;
struct authenc_request_ctx *areq_ctx = aead_request_ctx(req);
struct ahash_request *ahreq = (void *)(areq_ctx->tail + ictx->reqoff);
u8 *hash = areq_ctx->tail;
int err;
hash = (u8 *)ALIGN((unsigned long)hash + crypto_ahash_alignmask(auth),
crypto_ahash_alignmask(auth) + 1);
ahash_request_set_tfm(ahreq, auth);
ahash_request_set_crypt(ahreq, req->src, hash,
req->assoclen + req->cryptlen - authsize);
ahash_request_set_callback(ahreq, aead_request_flags(req),
authenc_verify_ahash_done, req);
err = crypto_ahash_digest(ahreq);
if (err)
return err;
return crypto_authenc_decrypt_tail(req, aead_request_flags(req));
}
static int crypto_authenc_init_tfm(struct crypto_aead *tfm)
{
struct aead_instance *inst = aead_alg_instance(tfm);
struct authenc_instance_ctx *ictx = aead_instance_ctx(inst);
struct crypto_authenc_ctx *ctx = crypto_aead_ctx(tfm);
struct crypto_ahash *auth;
struct crypto_skcipher *enc;
struct crypto_skcipher *null;
int err;
auth = crypto_spawn_ahash(&ictx->auth);
if (IS_ERR(auth))
return PTR_ERR(auth);
enc = crypto_spawn_skcipher(&ictx->enc);
err = PTR_ERR(enc);
if (IS_ERR(enc))
goto err_free_ahash;
null = crypto_get_default_null_skcipher2();
err = PTR_ERR(null);
if (IS_ERR(null))
goto err_free_skcipher;
ctx->auth = auth;
ctx->enc = enc;
ctx->null = null;
crypto_aead_set_reqsize(
tfm,
sizeof(struct authenc_request_ctx) +
ictx->reqoff +
max_t(unsigned int,
crypto_ahash_reqsize(auth) +
sizeof(struct ahash_request),
sizeof(struct skcipher_request) +
crypto_skcipher_reqsize(enc)));
return 0;
err_free_skcipher:
crypto_free_skcipher(enc);
err_free_ahash:
crypto_free_ahash(auth);
return err;
}
static void crypto_authenc_exit_tfm(struct crypto_aead *tfm)
{
struct crypto_authenc_ctx *ctx = crypto_aead_ctx(tfm);
crypto_free_ahash(ctx->auth);
crypto_free_skcipher(ctx->enc);
crypto_put_default_null_skcipher2();
}
static void crypto_authenc_free(struct aead_instance *inst)
{
struct authenc_instance_ctx *ctx = aead_instance_ctx(inst);
crypto_drop_skcipher(&ctx->enc);
crypto_drop_ahash(&ctx->auth);
kfree(inst);
}
static int crypto_authenc_create(struct crypto_template *tmpl,
struct rtattr **tb)
{
struct crypto_attr_type *algt;
struct aead_instance *inst;
struct hash_alg_common *auth;
struct crypto_alg *auth_base;
struct skcipher_alg *enc;
struct authenc_instance_ctx *ctx;
const char *enc_name;
int err;
algt = crypto_get_attr_type(tb);
if (IS_ERR(algt))
return PTR_ERR(algt);
if ((algt->type ^ CRYPTO_ALG_TYPE_AEAD) & algt->mask)
return -EINVAL;
auth = ahash_attr_alg(tb[1], CRYPTO_ALG_TYPE_HASH,
CRYPTO_ALG_TYPE_AHASH_MASK |
crypto_requires_sync(algt->type, algt->mask));
if (IS_ERR(auth))
return PTR_ERR(auth);
auth_base = &auth->base;
enc_name = crypto_attr_alg_name(tb[2]);
err = PTR_ERR(enc_name);
if (IS_ERR(enc_name))
goto out_put_auth;
inst = kzalloc(sizeof(*inst) + sizeof(*ctx), GFP_KERNEL);
err = -ENOMEM;
if (!inst)
goto out_put_auth;
ctx = aead_instance_ctx(inst);
err = crypto_init_ahash_spawn(&ctx->auth, auth,
aead_crypto_instance(inst));
if (err)
goto err_free_inst;
crypto_set_skcipher_spawn(&ctx->enc, aead_crypto_instance(inst));
err = crypto_grab_skcipher(&ctx->enc, enc_name, 0,
crypto_requires_sync(algt->type,
algt->mask));
if (err)
goto err_drop_auth;
enc = crypto_spawn_skcipher_alg(&ctx->enc);
ctx->reqoff = ALIGN(2 * auth->digestsize + auth_base->cra_alignmask,
auth_base->cra_alignmask + 1);
err = -ENAMETOOLONG;
if (snprintf(inst->alg.base.cra_name, CRYPTO_MAX_ALG_NAME,
"authenc(%s,%s)", auth_base->cra_name,
enc->base.cra_name) >=
CRYPTO_MAX_ALG_NAME)
goto err_drop_enc;
if (snprintf(inst->alg.base.cra_driver_name, CRYPTO_MAX_ALG_NAME,
"authenc(%s,%s)", auth_base->cra_driver_name,
enc->base.cra_driver_name) >= CRYPTO_MAX_ALG_NAME)
goto err_drop_enc;
inst->alg.base.cra_flags = (auth_base->cra_flags |
enc->base.cra_flags) & CRYPTO_ALG_ASYNC;
inst->alg.base.cra_priority = enc->base.cra_priority * 10 +
auth_base->cra_priority;
inst->alg.base.cra_blocksize = enc->base.cra_blocksize;
inst->alg.base.cra_alignmask = auth_base->cra_alignmask |
enc->base.cra_alignmask;
inst->alg.base.cra_ctxsize = sizeof(struct crypto_authenc_ctx);
inst->alg.ivsize = crypto_skcipher_alg_ivsize(enc);
inst->alg.chunksize = crypto_skcipher_alg_chunksize(enc);
inst->alg.maxauthsize = auth->digestsize;
inst->alg.init = crypto_authenc_init_tfm;
inst->alg.exit = crypto_authenc_exit_tfm;
inst->alg.setkey = crypto_authenc_setkey;
inst->alg.encrypt = crypto_authenc_encrypt;
inst->alg.decrypt = crypto_authenc_decrypt;
inst->free = crypto_authenc_free;
err = aead_register_instance(tmpl, inst);
if (err)
goto err_drop_enc;
out:
crypto_mod_put(auth_base);
return err;
err_drop_enc:
crypto_drop_skcipher(&ctx->enc);
err_drop_auth:
crypto_drop_ahash(&ctx->auth);
err_free_inst:
kfree(inst);
out_put_auth:
goto out;
}
static struct crypto_template crypto_authenc_tmpl = {
.name = "authenc",
.create = crypto_authenc_create,
.module = THIS_MODULE,
};
static int __init crypto_authenc_module_init(void)
{
return crypto_register_template(&crypto_authenc_tmpl);
}
static void __exit crypto_authenc_module_exit(void)
{
crypto_unregister_template(&crypto_authenc_tmpl);
}
module_init(crypto_authenc_module_init);
module_exit(crypto_authenc_module_exit);
MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("Simple AEAD wrapper for IPsec");
MODULE_ALIAS_CRYPTO("authenc");
Computing file changes ...
