[PATCH v3] cpufreq/pasemi: fix an use-after-free in pas_cpufreq_cpu_init()

Subsystems: cpu frequency scaling framework, linux for powerpc (32-bit and 64-bit), the rest

STALE2651d

4 messages, 4 authors, 2019-07-09 · open the first message on its own page

[PATCH v3] cpufreq/pasemi: fix an use-after-free in pas_cpufreq_cpu_init()

From: Wen Yang <hidden>
Date: 2019-07-08 08:52:03

The cpu variable is still being used in the of_get_property() call
after the of_node_put() call, which may result in use-after-free.

Fixes: a9acc26b75f ("cpufreq/pasemi: fix possible object reference leak")
Signed-off-by: Wen Yang <redacted>
Cc: "Rafael J. Wysocki" <redacted>
Cc: Viresh Kumar <viresh.kumar@linaro.org>
Cc: linuxppc-dev@lists.ozlabs.org
Cc: linux-pm@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
---
v3: fix a leaked reference.
v2: clean up the code according to the advice of viresh.

 drivers/cpufreq/pasemi-cpufreq.c | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/drivers/cpufreq/pasemi-cpufreq.c b/drivers/cpufreq/pasemi-cpufreq.c
index 6b1e4ab..9dc5163 100644
--- a/drivers/cpufreq/pasemi-cpufreq.c
+++ b/drivers/cpufreq/pasemi-cpufreq.c

@@ -128,20 +128,20 @@ static int pas_cpufreq_cpu_init(struct cpufreq_policy *policy)
 	int cur_astate, idx;
 	struct resource res;
 	struct device_node *cpu, *dn;
-	int err = -ENODEV;
+	int err;
 
 	cpu = of_get_cpu_node(policy->cpu, NULL);
-
-	of_node_put(cpu);
 	if (!cpu)
-		goto out;
+		return -ENODEV;
 
 	dn = of_find_compatible_node(NULL, NULL, "1682m-sdc");
 	if (!dn)
 		dn = of_find_compatible_node(NULL, NULL,
 					     "pasemi,pwrficient-sdc");
-	if (!dn)
+	if (!dn) {
+		err = -ENODEV;
 		goto out;
+	}
 	err = of_address_to_resource(dn, 0, &res);
 	of_node_put(dn);
 	if (err)

@@ -196,6 +196,7 @@ static int pas_cpufreq_cpu_init(struct cpufreq_policy *policy)
 	policy->cur = pas_freqs[cur_astate].frequency;
 	ppc_proc_freq = policy->cur * 1000ul;
 
+	of_node_put(cpu);
 	return cpufreq_generic_init(policy, pas_freqs, get_gizmo_latency());
 
 out_unmap_sdcpwr:

@@ -204,6 +205,7 @@ static int pas_cpufreq_cpu_init(struct cpufreq_policy *policy)
 out_unmap_sdcasr:
 	iounmap(sdcasr_mapbase);
 out:
+	of_node_put(cpu);
 	return err;
 }

-- 
2.9.5

Re: [PATCH v3] cpufreq/pasemi: fix an use-after-free in pas_cpufreq_cpu_init()

From: Viresh Kumar <viresh.kumar@linaro.org>
Date: 2019-07-08 08:56:11

On 08-07-19, 16:48, Wen Yang wrote:

quoted hunk

The cpu variable is still being used in the of_get_property() call
after the of_node_put() call, which may result in use-after-free.

Fixes: a9acc26b75f ("cpufreq/pasemi: fix possible object reference leak")
Signed-off-by: Wen Yang <redacted>
Cc: "Rafael J. Wysocki" <redacted>
Cc: Viresh Kumar <viresh.kumar@linaro.org>
Cc: linuxppc-dev@lists.ozlabs.org
Cc: linux-pm@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
---
v3: fix a leaked reference.
v2: clean up the code according to the advice of viresh.

 drivers/cpufreq/pasemi-cpufreq.c | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/drivers/cpufreq/pasemi-cpufreq.c b/drivers/cpufreq/pasemi-cpufreq.c
index 6b1e4ab..9dc5163 100644
--- a/drivers/cpufreq/pasemi-cpufreq.c
+++ b/drivers/cpufreq/pasemi-cpufreq.c

@@ -128,20 +128,20 @@ static int pas_cpufreq_cpu_init(struct cpufreq_policy *policy)
 	int cur_astate, idx;
 	struct resource res;
 	struct device_node *cpu, *dn;
-	int err = -ENODEV;
+	int err;
 
 	cpu = of_get_cpu_node(policy->cpu, NULL);
-
-	of_node_put(cpu);
 	if (!cpu)
-		goto out;
+		return -ENODEV;
 
 	dn = of_find_compatible_node(NULL, NULL, "1682m-sdc");
 	if (!dn)
 		dn = of_find_compatible_node(NULL, NULL,
 					     "pasemi,pwrficient-sdc");
-	if (!dn)
+	if (!dn) {
+		err = -ENODEV;
 		goto out;
+	}

Please restore the blank line here.

quoted hunk

 	err = of_address_to_resource(dn, 0, &res);
 	of_node_put(dn);
 	if (err)

@@ -196,6 +196,7 @@ static int pas_cpufreq_cpu_init(struct cpufreq_policy *policy)
 	policy->cur = pas_freqs[cur_astate].frequency;
 	ppc_proc_freq = policy->cur * 1000ul;
 
+	of_node_put(cpu);
 	return cpufreq_generic_init(policy, pas_freqs, get_gizmo_latency());
 
 out_unmap_sdcpwr:

@@ -204,6 +205,7 @@ static int pas_cpufreq_cpu_init(struct cpufreq_policy *policy)
 out_unmap_sdcasr:
 	iounmap(sdcasr_mapbase);
 out:
+	of_node_put(cpu);
 	return err;
 }

-- 
2.9.5

-- 
viresh

Re: [PATCH v3] cpufreq/pasemi: fix an use-after-free in pas_cpufreq_cpu_init()

From: Markus Elfring <hidden>
Date: 2019-07-08 17:45:47

quoted hunk

@@ -204,6 +205,7 @@  static int pas_cpufreq_cpu_init(struct cpufreq_policy *policy)

 out_unmap_sdcasr:

 	iounmap(sdcasr_mapbase);

 out:

+	of_node_put(cpu);


I would find the usage of a jump label like “put_node” nicer at such
a source code place.

Regards,
Markus

Re: [PATCH v3] cpufreq/pasemi: fix an use-after-free in pas_cpufreq_cpu_init()

From: Michael Ellerman <mpe@ellerman.id.au>
Date: 2019-07-09 04:47:08

Wen Yang [off-list ref] writes:

quoted hunk

The cpu variable is still being used in the of_get_property() call
after the of_node_put() call, which may result in use-after-free.

Fixes: a9acc26b75f ("cpufreq/pasemi: fix possible object reference leak")
Signed-off-by: Wen Yang <redacted>
Cc: "Rafael J. Wysocki" <redacted>
Cc: Viresh Kumar <viresh.kumar@linaro.org>
Cc: linuxppc-dev@lists.ozlabs.org
Cc: linux-pm@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
---
v3: fix a leaked reference.
v2: clean up the code according to the advice of viresh.

 drivers/cpufreq/pasemi-cpufreq.c | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/drivers/cpufreq/pasemi-cpufreq.c b/drivers/cpufreq/pasemi-cpufreq.c
index 6b1e4ab..9dc5163 100644
--- a/drivers/cpufreq/pasemi-cpufreq.c
+++ b/drivers/cpufreq/pasemi-cpufreq.c

@@ -128,20 +128,20 @@ static int pas_cpufreq_cpu_init(struct cpufreq_policy *policy)
 	int cur_astate, idx;
 	struct resource res;
 	struct device_node *cpu, *dn;
-	int err = -ENODEV;
+	int err;
 
 	cpu = of_get_cpu_node(policy->cpu, NULL);
-
-	of_node_put(cpu);
 	if (!cpu)
-		goto out;
+		return -ENODEV;

I don't think introducing another exit path is an improvement.

quoted hunk

 	dn = of_find_compatible_node(NULL, NULL, "1682m-sdc");
 	if (!dn)
 		dn = of_find_compatible_node(NULL, NULL,
 					     "pasemi,pwrficient-sdc");
-	if (!dn)
+	if (!dn) {
+		err = -ENODEV;
 		goto out;
+	}
 	err = of_address_to_resource(dn, 0, &res);
 	of_node_put(dn);
 	if (err)

@@ -196,6 +196,7 @@ static int pas_cpufreq_cpu_init(struct cpufreq_policy *policy)
 	policy->cur = pas_freqs[cur_astate].frequency;
 	ppc_proc_freq = policy->cur * 1000ul;
 
+	of_node_put(cpu);
 	return cpufreq_generic_init(policy, pas_freqs, get_gizmo_latency());
 
 out_unmap_sdcpwr:
@@ -204,6 +205,7 @@ static int pas_cpufreq_cpu_init(struct cpufreq_policy *policy)
 out_unmap_sdcasr:
 	iounmap(sdcasr_mapbase);
 out:
+	of_node_put(cpu);
 	return err;
 }

Notice that cpu is only used for the max_freq calculation, so we could
instead do:

diff --git a/drivers/cpufreq/pasemi-cpufreq.c b/drivers/cpufreq/pasemi-cpufreq.c
index 6b1e4abe3248..42a0a4b8e87d 100644
--- a/drivers/cpufreq/pasemi-cpufreq.c
+++ b/drivers/cpufreq/pasemi-cpufreq.c

@@ -131,11 +131,20 @@ static int pas_cpufreq_cpu_init(struct cpufreq_policy *policy)
 	int err = -ENODEV;
 
 	cpu = of_get_cpu_node(policy->cpu, NULL);
-
-	of_node_put(cpu);
 	if (!cpu)
 		goto out;
 
+	max_freqp = of_get_property(cpu, "clock-frequency", NULL);
+	if (!max_freqp) {
+		of_node_put(cpu);
+		err = -EINVAL;
+		goto out;
+	}
+
+	/* we need the freq in kHz */
+	max_freq = *max_freqp / 1000;
+	of_node_put(cpu);
+
 	dn = of_find_compatible_node(NULL, NULL, "1682m-sdc");
 	if (!dn)
 		dn = of_find_compatible_node(NULL, NULL,

@@ -172,15 +181,6 @@ static int pas_cpufreq_cpu_init(struct cpufreq_policy *policy)
 
 	pr_debug("init cpufreq on CPU %d\n", policy->cpu);
 
-	max_freqp = of_get_property(cpu, "clock-frequency", NULL);
-	if (!max_freqp) {
-		err = -EINVAL;
-		goto out_unmap_sdcpwr;
-	}
-
-	/* we need the freq in kHz */
-	max_freq = *max_freqp / 1000;
-
 	pr_debug("max clock-frequency is at %u kHz\n", max_freq);
 	pr_debug("initializing frequency table\n");

Though arguably this function should hold a reference to cpu anyway,
because it doesn't want the CPU to removed out from under it. It's a
CPUfreq driver after all.

cheers

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