Hi Robert,

On Fri, 2010-08-27 at 13:43 +0100, Robert Richter wrote:

On 26.08.10 15:09:16, Matt Fleming wrote:

quoted

From: Will Deacon <redacted>

The current implementation is not entirely safe in the case that
oprofile_arch_init() fails. We need to make sure that we always call
exit_driverfs() if we've called init_driverfs(). Also, avoid a potential
double free when freeing 'counter_config', e.g. don't free
'counter_config' in both oprofile_arch_init() and oprofile_arch_exit().

Signed-off-by: Will Deacon <redacted>
---
 arch/arm/oprofile/common.c |   15 ++++++++-------
 1 files changed, 8 insertions(+), 7 deletions(-)

diff --git a/arch/arm/oprofile/common.c b/arch/arm/oprofile/common.c
index 0691176..482779c 100644
--- a/arch/arm/oprofile/common.c
+++ b/arch/arm/oprofile/common.c

@@ -275,10 +275,12 @@ out:
      return ret;
 }

-static void  exit_driverfs(void)
+static void exit_driverfs(void)
 {
-     platform_device_unregister(oprofile_pdev);
-     platform_driver_unregister(&oprofile_driver);
+     if (!IS_ERR_OR_NULL(oprofile_pdev)) {
+             platform_device_unregister(oprofile_pdev);
+             platform_driver_unregister(&oprofile_driver);
+     }

The root cause that makes this check necessary is that
oprofile_arch_exit() is called though oprofile_arch_init() failed. We
should better fix this instead. I have to admit we will then have to
check all architectural implementations.

I took a look through all of the oprofile_arch_{init,exit} functions
and it looks like only ARM needs fixing. Nobody else does any allocation
here [well, until Matt's unified version comes into play].

quoted

 }
 #else
 static int __init init_driverfs(void) { return 0; }

@@ -363,10 +365,8 @@ int __init oprofile_arch_init(struct oprofile_operations *ops)
      }

      ret = init_driverfs();
-     if (ret) {
-             kfree(counter_config);

We should not return from oprofile_arch_init() with allocated
resources if the function fails. To fix duplicate kfrees, we should
free it here and then set counter_config to NULL. It should also be
freed if for_each_possible_cpu() or op_name_from_perf_id() fails.

Also, the pointer should be NULLed after freeing in
oprofile_arch_exit(). There, we also don't need the NULL pointer check
as it is save to call kfree(NULL).

How about something like this? This removes the exit call
from the init code and sets pointers to NULL after they have been
freed. We still have to do some checking so that we don't try to
release a NULL perf event:

diff --git a/arch/arm/oprofile/common.c b/arch/arm/oprofile/common.c
index 0691176..12253eb 100644
--- a/arch/arm/oprofile/common.c
+++ b/arch/arm/oprofile/common.c

@@ -275,10 +275,12 @@ out:
 	return ret;
 }
 
-static void  exit_driverfs(void)
+static void __exit exit_driverfs(void)
 {
-	platform_device_unregister(oprofile_pdev);
-	platform_driver_unregister(&oprofile_driver);
+	if (!IS_ERR_OR_NULL(oprofile_pdev)) {
+		platform_device_unregister(oprofile_pdev);
+		platform_driver_unregister(&oprofile_driver);
+	}
 }
 #else
 static int __init init_driverfs(void) { return 0; }

@@ -365,6 +367,7 @@ int __init oprofile_arch_init(struct

oprofile_operations *ops)
 	ret = init_driverfs();
 	if (ret) {
 		kfree(counter_config);
+		counter_config = NULL;
 		return ret;
 	}
 

@@ -374,8 +377,10 @@ int __init oprofile_arch_init(struct

oprofile_operations *ops)
 		if (!perf_events[cpu]) {
 			pr_info("oprofile: failed to allocate %d perf events "
 					"for cpu %d\n", perf_num_counters, cpu);
-			while (--cpu >= 0)
+			while (--cpu >= 0) {
 				kfree(perf_events[cpu]);
+				perf_events[cpu] = NULL;
+			}
 			return -ENOMEM;
 		}
 	}

@@ -396,25 +401,27 @@ int __init oprofile_arch_init(struct

oprofile_operations *ops)
 	return ret;
 }
 
-void oprofile_arch_exit(void)
+void __exit oprofile_arch_exit(void)
 {
 	int cpu, id;
 	struct perf_event *event;
 
-	if (*perf_events) {
-		exit_driverfs();
-		for_each_possible_cpu(cpu) {
-			for (id = 0; id < perf_num_counters; ++id) {
-				event = perf_events[cpu][id];
-				if (event != NULL)
-					perf_event_release_kernel(event);
-			}
-			kfree(perf_events[cpu]);
+	exit_driverfs();
+
+	for_each_possible_cpu(cpu) {
+		if (!perf_events[cpu])
+			continue;
+
+		for (id = 0; id < perf_num_counters; ++id) {
+			event = perf_events[cpu][id];
+			if (event != NULL)
+				perf_event_release_kernel(event);
 		}
+
+		kfree(perf_events[cpu]);
 	}
 
-	if (counter_config)
-		kfree(counter_config);
+	kfree(counter_config);
 }
 #else
 int __init oprofile_arch_init(struct oprofile_operations *ops)

@@ -422,5 +429,5 @@ int __init oprofile_arch_init(struct

oprofile_operations *ops)
 	pr_info("oprofile: hardware counters not available\n");
 	return -ENODEV;
 }
-void oprofile_arch_exit(void) {}
+void __exit oprofile_arch_exit(void) {}
 #endif /* CONFIG_HW_PERF_EVENTS */

diff --git a/drivers/oprofile/oprof.c b/drivers/oprofile/oprof.c
index b336cd9..3094af0 100644
--- a/drivers/oprofile/oprof.c
+++ b/drivers/oprofile/oprof.c

@@ -257,15 +257,11 @@ static int __init oprofile_init(void)
 		printk(KERN_INFO "oprofile: using timer interrupt.\n");
 		err = oprofile_timer_init(&oprofile_ops);
 		if (err)
-			goto out_arch;
+			goto out;
 	}
 	err = oprofilefs_register();
-	if (err)
-		goto out_arch;
-	return 0;
 
-out_arch:
-	oprofile_arch_exit();
+out:
 	return err;
 }
 

Thanks,

Will