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Subject[tip:x86/cache] x86/intel_rdt: Prevent pseudo-locking from using stale pointers
Commit-ID:  b61b8bba18fe2b63d38fdaf9b83de25e2d787dfe
Gitweb: https://git.kernel.org/tip/b61b8bba18fe2b63d38fdaf9b83de25e2d787dfe
Author: Jithu Joseph <jithu.joseph@intel.com>
AuthorDate: Fri, 12 Oct 2018 15:51:01 -0700
Committer: Thomas Gleixner <tglx@linutronix.de>
CommitDate: Fri, 19 Oct 2018 14:54:28 +0200

x86/intel_rdt: Prevent pseudo-locking from using stale pointers

When the last CPU in an rdt_domain goes offline, its rdt_domain struct gets
freed. Current pseudo-locking code is unaware of this scenario and tries to
dereference the freed structure in a few places.

Add checks to prevent pseudo-locking code from doing this.

While further work is needed to seamlessly restore resource groups (not
just pseudo-locking) to their configuration when the domain is brought back
online, the immediate issue of invalid pointers is addressed here.

Fixes: f4e80d67a5274 ("x86/intel_rdt: Resctrl files reflect pseudo-locked information")
Fixes: 443810fe61605 ("x86/intel_rdt: Create debugfs files for pseudo-locking testing")
Fixes: 746e08590b864 ("x86/intel_rdt: Create character device exposing pseudo-locked region")
Fixes: 33dc3e410a0d9 ("x86/intel_rdt: Make CPU information accessible for pseudo-locked regions")
Signed-off-by: Jithu Joseph <jithu.joseph@intel.com>
Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: fenghua.yu@intel.com
Cc: tony.luck@intel.com
Cc: gavin.hindman@intel.com
Cc: hpa@zytor.com
Link: https://lkml.kernel.org/r/231f742dbb7b00a31cc104416860e27dba6b072d.1539384145.git.reinette.chatre@intel.com

---
arch/x86/kernel/cpu/intel_rdt.c | 7 ++++++
arch/x86/kernel/cpu/intel_rdt_ctrlmondata.c | 12 +++++++--
arch/x86/kernel/cpu/intel_rdt_pseudo_lock.c | 10 ++++++++
arch/x86/kernel/cpu/intel_rdt_rdtgroup.c | 38 +++++++++++++++++++++--------
4 files changed, 55 insertions(+), 12 deletions(-)

diff --git a/arch/x86/kernel/cpu/intel_rdt.c b/arch/x86/kernel/cpu/intel_rdt.c
index 1214f3f7ec6d..44272b7107ad 100644
--- a/arch/x86/kernel/cpu/intel_rdt.c
+++ b/arch/x86/kernel/cpu/intel_rdt.c
@@ -608,6 +608,13 @@ static void domain_remove_cpu(int cpu, struct rdt_resource *r)
cancel_delayed_work(&d->cqm_limbo);
}

+ /*
+ * rdt_domain "d" is going to be freed below, so clear
+ * its pointer from pseudo_lock_region struct.
+ */
+ if (d->plr)
+ d->plr->d = NULL;
+
kfree(d->ctrl_val);
kfree(d->mbps_val);
bitmap_free(d->rmid_busy_llc);
diff --git a/arch/x86/kernel/cpu/intel_rdt_ctrlmondata.c b/arch/x86/kernel/cpu/intel_rdt_ctrlmondata.c
index 0f53049719cd..27937458c231 100644
--- a/arch/x86/kernel/cpu/intel_rdt_ctrlmondata.c
+++ b/arch/x86/kernel/cpu/intel_rdt_ctrlmondata.c
@@ -404,8 +404,16 @@ int rdtgroup_schemata_show(struct kernfs_open_file *of,
for_each_alloc_enabled_rdt_resource(r)
seq_printf(s, "%s:uninitialized\n", r->name);
} else if (rdtgrp->mode == RDT_MODE_PSEUDO_LOCKED) {
- seq_printf(s, "%s:%d=%x\n", rdtgrp->plr->r->name,
- rdtgrp->plr->d->id, rdtgrp->plr->cbm);
+ if (!rdtgrp->plr->d) {
+ rdt_last_cmd_clear();
+ rdt_last_cmd_puts("Cache domain offline\n");
+ ret = -ENODEV;
+ } else {
+ seq_printf(s, "%s:%d=%x\n",
+ rdtgrp->plr->r->name,
+ rdtgrp->plr->d->id,
+ rdtgrp->plr->cbm);
+ }
} else {
closid = rdtgrp->closid;
for_each_alloc_enabled_rdt_resource(r) {
diff --git a/arch/x86/kernel/cpu/intel_rdt_pseudo_lock.c b/arch/x86/kernel/cpu/intel_rdt_pseudo_lock.c
index 41aeb431e834..966ac0c20d67 100644
--- a/arch/x86/kernel/cpu/intel_rdt_pseudo_lock.c
+++ b/arch/x86/kernel/cpu/intel_rdt_pseudo_lock.c
@@ -1174,6 +1174,11 @@ static int pseudo_lock_measure_cycles(struct rdtgroup *rdtgrp, int sel)
goto out;
}

+ if (!plr->d) {
+ ret = -ENODEV;
+ goto out;
+ }
+
plr->thread_done = 0;
cpu = cpumask_first(&plr->d->cpu_mask);
if (!cpu_online(cpu)) {
@@ -1494,6 +1499,11 @@ static int pseudo_lock_dev_mmap(struct file *filp, struct vm_area_struct *vma)

plr = rdtgrp->plr;

+ if (!plr->d) {
+ mutex_unlock(&rdtgroup_mutex);
+ return -ENODEV;
+ }
+
/*
* Task is required to run with affinity to the cpus associated
* with the pseudo-locked region. If this is not the case the task
diff --git a/arch/x86/kernel/cpu/intel_rdt_rdtgroup.c b/arch/x86/kernel/cpu/intel_rdt_rdtgroup.c
index dbc7fc98b60a..f27b8115ffa2 100644
--- a/arch/x86/kernel/cpu/intel_rdt_rdtgroup.c
+++ b/arch/x86/kernel/cpu/intel_rdt_rdtgroup.c
@@ -268,17 +268,27 @@ static int rdtgroup_cpus_show(struct kernfs_open_file *of,
struct seq_file *s, void *v)
{
struct rdtgroup *rdtgrp;
+ struct cpumask *mask;
int ret = 0;

rdtgrp = rdtgroup_kn_lock_live(of->kn);

if (rdtgrp) {
- if (rdtgrp->mode == RDT_MODE_PSEUDO_LOCKED)
- seq_printf(s, is_cpu_list(of) ? "%*pbl\n" : "%*pb\n",
- cpumask_pr_args(&rdtgrp->plr->d->cpu_mask));
- else
+ if (rdtgrp->mode == RDT_MODE_PSEUDO_LOCKED) {
+ if (!rdtgrp->plr->d) {
+ rdt_last_cmd_clear();
+ rdt_last_cmd_puts("Cache domain offline\n");
+ ret = -ENODEV;
+ } else {
+ mask = &rdtgrp->plr->d->cpu_mask;
+ seq_printf(s, is_cpu_list(of) ?
+ "%*pbl\n" : "%*pb\n",
+ cpumask_pr_args(mask));
+ }
+ } else {
seq_printf(s, is_cpu_list(of) ? "%*pbl\n" : "%*pb\n",
cpumask_pr_args(&rdtgrp->cpu_mask));
+ }
} else {
ret = -ENOENT;
}
@@ -1282,6 +1292,7 @@ static int rdtgroup_size_show(struct kernfs_open_file *of,
struct rdt_resource *r;
struct rdt_domain *d;
unsigned int size;
+ int ret = 0;
bool sep;
u32 ctrl;

@@ -1292,11 +1303,18 @@ static int rdtgroup_size_show(struct kernfs_open_file *of,
}

if (rdtgrp->mode == RDT_MODE_PSEUDO_LOCKED) {
- seq_printf(s, "%*s:", max_name_width, rdtgrp->plr->r->name);
- size = rdtgroup_cbm_to_size(rdtgrp->plr->r,
- rdtgrp->plr->d,
- rdtgrp->plr->cbm);
- seq_printf(s, "%d=%u\n", rdtgrp->plr->d->id, size);
+ if (!rdtgrp->plr->d) {
+ rdt_last_cmd_clear();
+ rdt_last_cmd_puts("Cache domain offline\n");
+ ret = -ENODEV;
+ } else {
+ seq_printf(s, "%*s:", max_name_width,
+ rdtgrp->plr->r->name);
+ size = rdtgroup_cbm_to_size(rdtgrp->plr->r,
+ rdtgrp->plr->d,
+ rdtgrp->plr->cbm);
+ seq_printf(s, "%d=%u\n", rdtgrp->plr->d->id, size);
+ }
goto out;
}

@@ -1326,7 +1344,7 @@ static int rdtgroup_size_show(struct kernfs_open_file *of,
out:
rdtgroup_kn_unlock(of->kn);

- return 0;
+ return ret;
}

/* rdtgroup information files for one cache resource. */
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