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Subject[PATCH v2 1/5] padata: validate cpumask without removed CPU during offline
Date
Configuring an instance's parallel mask without any online CPUs...

echo 2 > /sys/kernel/pcrypt/pencrypt/parallel_cpumask
echo 0 > /sys/devices/system/cpu/cpu1/online

...makes tcrypt mode=215 crash like this:

divide error: 0000 [#1] SMP PTI
CPU: 4 PID: 283 Comm: modprobe Not tainted 5.4.0-rc8-padata-doc-v2+ #2
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS ?-20191013_105130-anatol 04/01/2014
RIP: 0010:padata_do_parallel+0x114/0x300
Call Trace:
pcrypt_aead_encrypt+0xc0/0xd0 [pcrypt]
crypto_aead_encrypt+0x1f/0x30
do_mult_aead_op+0x4e/0xdf [tcrypt]
test_mb_aead_speed.constprop.0.cold+0x226/0x564 [tcrypt]
do_test+0x28c2/0x4d49 [tcrypt]
tcrypt_mod_init+0x55/0x1000 [tcrypt]
...

cpumask_weight() in padata_cpu_hash() returns 0 because the mask has no
CPUs. The problem is __padata_remove_cpu() checks for valid masks too
early and so doesn't mark the instance PADATA_INVALID as expected, which
would have made padata_do_parallel() return error before doing the
division.

Fix by introducing a second padata CPU hotplug state before
CPUHP_BRINGUP_CPU so that __padata_remove_cpu() sees the online mask
without @cpu. No need for the second argument to padata_replace() since
@cpu is now already missing from the online mask.

Fixes: 33e54450683c ("padata: Handle empty padata cpumasks")
Signed-off-by: Daniel Jordan <daniel.m.jordan@oracle.com>
Cc: Eric Biggers <ebiggers@kernel.org>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Steffen Klassert <steffen.klassert@secunet.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-crypto@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
---
include/linux/cpuhotplug.h | 1 +
kernel/padata.c | 30 ++++++++++++++++++------------
2 files changed, 19 insertions(+), 12 deletions(-)

diff --git a/include/linux/cpuhotplug.h b/include/linux/cpuhotplug.h
index 068793a619ca..2d55cee638fc 100644
--- a/include/linux/cpuhotplug.h
+++ b/include/linux/cpuhotplug.h
@@ -59,6 +59,7 @@ enum cpuhp_state {
CPUHP_IOMMU_INTEL_DEAD,
CPUHP_LUSTRE_CFS_DEAD,
CPUHP_AP_ARM_CACHE_B15_RAC_DEAD,
+ CPUHP_PADATA_DEAD,
CPUHP_WORKQUEUE_PREP,
CPUHP_POWER_NUMA_PREPARE,
CPUHP_HRTIMERS_PREPARE,
diff --git a/kernel/padata.c b/kernel/padata.c
index 9e3c4df75907..a2fa6223e1a0 100644
--- a/kernel/padata.c
+++ b/kernel/padata.c
@@ -512,7 +512,7 @@ static int padata_replace_one(struct padata_shell *ps)
return 0;
}

-static int padata_replace(struct padata_instance *pinst, int cpu)
+static int padata_replace(struct padata_instance *pinst)
{
int notification_mask = 0;
struct padata_shell *ps;
@@ -523,16 +523,12 @@ static int padata_replace(struct padata_instance *pinst, int cpu)
cpumask_copy(pinst->omask, pinst->rcpumask.pcpu);
cpumask_and(pinst->rcpumask.pcpu, pinst->cpumask.pcpu,
cpu_online_mask);
- if (cpu >= 0)
- cpumask_clear_cpu(cpu, pinst->rcpumask.pcpu);
if (!cpumask_equal(pinst->omask, pinst->rcpumask.pcpu))
notification_mask |= PADATA_CPU_PARALLEL;

cpumask_copy(pinst->omask, pinst->rcpumask.cbcpu);
cpumask_and(pinst->rcpumask.cbcpu, pinst->cpumask.cbcpu,
cpu_online_mask);
- if (cpu >= 0)
- cpumask_clear_cpu(cpu, pinst->rcpumask.cbcpu);
if (!cpumask_equal(pinst->omask, pinst->rcpumask.cbcpu))
notification_mask |= PADATA_CPU_SERIAL;

@@ -624,7 +620,7 @@ static int __padata_set_cpumasks(struct padata_instance *pinst,
cpumask_copy(pinst->cpumask.pcpu, pcpumask);
cpumask_copy(pinst->cpumask.cbcpu, cbcpumask);

- err = padata_setup_cpumasks(pinst) ?: padata_replace(pinst, -1);
+ err = padata_setup_cpumasks(pinst) ?: padata_replace(pinst);

if (valid)
__padata_start(pinst);
@@ -715,7 +711,7 @@ static int __padata_add_cpu(struct padata_instance *pinst, int cpu)
int err = 0;

if (cpumask_test_cpu(cpu, cpu_online_mask)) {
- err = padata_replace(pinst, -1);
+ err = padata_replace(pinst);

if (padata_validate_cpumask(pinst, pinst->cpumask.pcpu) &&
padata_validate_cpumask(pinst, pinst->cpumask.cbcpu))
@@ -729,12 +725,12 @@ static int __padata_remove_cpu(struct padata_instance *pinst, int cpu)
{
int err = 0;

- if (cpumask_test_cpu(cpu, cpu_online_mask)) {
+ if (!cpumask_test_cpu(cpu, cpu_online_mask)) {
if (!padata_validate_cpumask(pinst, pinst->cpumask.pcpu) ||
!padata_validate_cpumask(pinst, pinst->cpumask.cbcpu))
__padata_stop(pinst);

- err = padata_replace(pinst, cpu);
+ err = padata_replace(pinst);
}

return err;
@@ -761,7 +757,7 @@ static int padata_cpu_online(unsigned int cpu, struct hlist_node *node)
return ret;
}

-static int padata_cpu_prep_down(unsigned int cpu, struct hlist_node *node)
+static int padata_cpu_dead(unsigned int cpu, struct hlist_node *node)
{
struct padata_instance *pinst;
int ret;
@@ -782,6 +778,7 @@ static enum cpuhp_state hp_online;
static void __padata_free(struct padata_instance *pinst)
{
#ifdef CONFIG_HOTPLUG_CPU
+ cpuhp_state_remove_instance_nocalls(CPUHP_PADATA_DEAD, &pinst->node);
cpuhp_state_remove_instance_nocalls(hp_online, &pinst->node);
#endif

@@ -989,6 +986,8 @@ static struct padata_instance *padata_alloc(const char *name,

#ifdef CONFIG_HOTPLUG_CPU
cpuhp_state_add_instance_nocalls_cpuslocked(hp_online, &pinst->node);
+ cpuhp_state_add_instance_nocalls_cpuslocked(CPUHP_PADATA_DEAD,
+ &pinst->node);
#endif

put_online_cpus();
@@ -1101,17 +1100,24 @@ static __init int padata_driver_init(void)
int ret;

ret = cpuhp_setup_state_multi(CPUHP_AP_ONLINE_DYN, "padata:online",
- padata_cpu_online,
- padata_cpu_prep_down);
+ padata_cpu_online, NULL);
if (ret < 0)
return ret;
hp_online = ret;
+
+ ret = cpuhp_setup_state_multi(CPUHP_PADATA_DEAD, "padata:dead",
+ NULL, padata_cpu_dead);
+ if (ret < 0) {
+ cpuhp_remove_multi_state(hp_online);
+ return ret;
+ }
return 0;
}
module_init(padata_driver_init);

static __exit void padata_driver_exit(void)
{
+ cpuhp_remove_multi_state(CPUHP_PADATA_DEAD);
cpuhp_remove_multi_state(hp_online);
}
module_exit(padata_driver_exit);
--
2.24.0
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