acer-wmi: fix memory leaks in wmab_execute error path

PATCH In review Axel Lin 2 participants 4 messages Jul 9, 2010 – Jul 13, 2010

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x86 platform drivers Acer WMI laptop extras

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Axel Lin

author

2010-07-09 04:37 UTC #0 lore raw

PATCH v2 1/1 acer-wmi: fix memory leaks in wmab_execute error path

When acpi_evaluate_object() is passed ACPI_ALLOCATE_BUFFER, the caller must kfree the returned buffer if AE_OK is returned.

Call Trace:
wmab_execute
  -> wmi_evaluate_method
    -> acpi_evaluate_object

Thus if callers of wmab_execute() pass ACPI_ALLOCATE_BUFFER, the return buffer must be kfreed if wmab_execute return AE_OK.

Signed-off-by Axel Lin <[email protected]>

---
 drivers/platform/x86/acer-wmi.c |   11 ++++++++++-
 1 files changed, 10 insertions(+), 1 deletions(-)

drivers/platform/x86/acer-wmi.c +10 -1

index 1ea6c43..3f44446 100644
@@ -555,6 +555,7 @@ static acpi_status AMW0_find_mailled(void)
 	obj->buffer.length == sizeof(struct wmab_ret)) {
 		ret = *((struct wmab_ret *) obj->buffer.pointer);
 	} else {
+		kfree(out.pointer);
 		return AE_ERROR;
 	}

@@ -598,6 +599,7 @@ static acpi_status AMW0_set_capabilities(void)
 	obj->buffer.length == sizeof(struct wmab_ret)) {
 		ret = *((struct wmab_ret *) obj->buffer.pointer);
 	} else {
+		kfree(out.pointer);
 		return AE_ERROR;
 	}

@@ -607,15 +609,22 @@ static acpi_status AMW0_set_capabilities(void)
 	args.ebx = 2 << 8;
 	args.ebx |= ACER_AMW0_BLUETOOTH_MASK;
 
+	/*
+	 * It's ok to use existing buffer for next wmab_execute call.
+	 * But we need to kfree(out.pointer) if next wmab_execute fail.
+	 */
 	status = wmab_execute(&args, &out);
-	if (ACPI_FAILURE(status))
+	if (ACPI_FAILURE(status)) {
+		kfree(out.pointer);
 		return status;
+	}
 
 	obj = (union acpi_object *) out.pointer;
 	if (obj && obj->type == ACPI_TYPE_BUFFER
 	&& obj->buffer.length == sizeof(struct wmab_ret)) {
 		ret = *((struct wmab_ret *) obj->buffer.pointer);
 	} else {
+		kfree(out.pointer);
 		return AE_ERROR;
 	}

Signature · 1 line

1.5.4.3

hi Andrew,
I just found acer-wmi-fix-memory-leaks-in-wmab_execute-error-path.patch added to -mm tree. But I think the V2 version is the correct one.
If the second wmab_execute fail (for any reason) , we need to free the existing buffer before return status. Sould I resend the patch?

Regards,
Axel

於五，2010-07-09 於 12:37 +0800，Axel Lin 提到：

Quoted 60 lines

When acpi_evaluate_object() is passed ACPI_ALLOCATE_BUFFER, the caller must kfree the returned buffer if AE_OK is returned.

Call Trace:
wmab_execute
  -> wmi_evaluate_method
    -> acpi_evaluate_object

Thus if callers of wmab_execute() pass ACPI_ALLOCATE_BUFFER, the return buffer must be kfreed if wmab_execute return AE_OK.

Signed-off-by Axel Lin <[email protected]>

---
 drivers/platform/x86/acer-wmi.c |   11 ++++++++++-
 1 files changed, 10 insertions(+), 1 deletions(-)

drivers/platform/x86/acer-wmi.c +10 -1

index 1ea6c43..3f44446 100644
@@ -555,6 +555,7 @@ static acpi_status AMW0_find_mailled(void)
 	obj->buffer.length == sizeof(struct wmab_ret)) {
 		ret = *((struct wmab_ret *) obj->buffer.pointer);
 	} else {
+		kfree(out.pointer);
 		return AE_ERROR;
 	}

@@ -598,6 +599,7 @@ static acpi_status AMW0_set_capabilities(void)
 	obj->buffer.length == sizeof(struct wmab_ret)) {
 		ret = *((struct wmab_ret *) obj->buffer.pointer);
 	} else {
+		kfree(out.pointer);
 		return AE_ERROR;
 	}

@@ -607,15 +609,22 @@ static acpi_status AMW0_set_capabilities(void)
 	args.ebx = 2 << 8;
 	args.ebx |= ACER_AMW0_BLUETOOTH_MASK;
 
+	/*
+	 * It's ok to use existing buffer for next wmab_execute call.
+	 * But we need to kfree(out.pointer) if next wmab_execute fail.
+	 */
 	status = wmab_execute(&args, &out);
-	if (ACPI_FAILURE(status))
+	if (ACPI_FAILURE(status)) {
+		kfree(out.pointer);
 		return status;
+	}
 
 	obj = (union acpi_object *) out.pointer;
 	if (obj && obj->type == ACPI_TYPE_BUFFER
 	&& obj->buffer.length == sizeof(struct wmab_ret)) {
 		ret = *((struct wmab_ret *) obj->buffer.pointer);
 	} else {
+		kfree(out.pointer);
 		return AE_ERROR;
 	}

Andrew Morton

2010-07-13 01:36 UTC #2 lore raw

In reply to Axel Lin

Quoted 49 lines · On Fri, 09 Jul 2010 12:37:36 +0800 Axel Lin <[email protected]> wrote:

When acpi_evaluate_object() is passed ACPI_ALLOCATE_BUFFER, the caller must kfree the returned buffer if AE_OK is returned.

Call Trace:
wmab_execute
  -> wmi_evaluate_method
    -> acpi_evaluate_object

Thus if callers of wmab_execute() pass ACPI_ALLOCATE_BUFFER, the return buffer must be kfreed if wmab_execute return AE_OK.

Signed-off-by Axel Lin <[email protected]>

---
 drivers/platform/x86/acer-wmi.c |   11 ++++++++++-
 1 files changed, 10 insertions(+), 1 deletions(-)

drivers/platform/x86/acer-wmi.c +8 -1

index 1ea6c43..3f44446 100644
@@ -555,6 +555,7 @@ static acpi_status AMW0_find_mailled(void)
 	obj->buffer.length == sizeof(struct wmab_ret)) {
 		ret = *((struct wmab_ret *) obj->buffer.pointer);
 	} else {
+		kfree(out.pointer);
 		return AE_ERROR;
 	}

@@ -598,6 +599,7 @@ static acpi_status AMW0_set_capabilities(void)
 	obj->buffer.length == sizeof(struct wmab_ret)) {
 		ret = *((struct wmab_ret *) obj->buffer.pointer);
 	} else {
+		kfree(out.pointer);
 		return AE_ERROR;
 	}

@@ -607,15 +609,22 @@ static acpi_status AMW0_set_capabilities(void)
 	args.ebx = 2 << 8;
 	args.ebx |= ACER_AMW0_BLUETOOTH_MASK;
 
+	/*
+	 * It's ok to use existing buffer for next wmab_execute call.
+	 * But we need to kfree(out.pointer) if next wmab_execute fail.
+	 */
 	status = wmab_execute(&args, &out);
-	if (ACPI_FAILURE(status))
+	if (ACPI_FAILURE(status)) {
+		kfree(out.pointer);
 		return status;

drivers/platform/x86/acer-wmi.c static acpi_status AMW0_set_capabilities(void) · line 629

Quoted 10 lines

drivers/platform/x86/acer-wmi.c +2 -0

+	}
 
 	obj = (union acpi_object *) out.pointer;
 	if (obj && obj->type == ACPI_TYPE_BUFFER
 	&& obj->buffer.length == sizeof(struct wmab_ret)) {
 		ret = *((struct wmab_ret *) obj->buffer.pointer);
 	} else {
+		kfree(out.pointer);
 		return AE_ERROR;
 	}

I think it's best to remove the multiple-return-points approach in favour of the "goto single return point which undoes things" approach. that way we reduce the risk of later introducing more leaks.

Please review:

From: Andrew Morton <[email protected]>

avoid multiple return points
remove unneeded cast
remove unneeded initialisation of `status'

Cc Alan Jenkins <[email protected]>

Cc Axel Lin <[email protected]>

Cc Carlos Corbacho <[email protected]>

Cc Matthew Garrett <[email protected]>

Cc Thomas Renninger <[email protected]>

Signed-off-by Andrew Morton <[email protected]>

---

 drivers/platform/x86/acer-wmi.c |   25 ++++++++++++-------------
 1 file changed, 12 insertions(+), 13 deletions(-)

drivers/platform/x86/acer-wmi.c renamed from drivers/platform/x86/acer-wmi.c~acer-wmi-fix-memory-leaks-in-wmab_execute-error-path-v2-fix +12 ~~-13~~

diff -puN drivers/platform/x86/acer-wmi.c~acer-wmi-fix-memory-leaks-in-wmab_execute-error-path-v2-fix drivers/platform/x86/acer-wmi.c
@@ -571,7 +571,7 @@ static acpi_status AMW0_set_capabilities
 {
 	struct wmab_args args;
 	struct wmab_ret ret;
-	acpi_status status = AE_OK;
+	acpi_status status;
 	struct acpi_buffer out = { ACPI_ALLOCATE_BUFFER, NULL };
 	union acpi_object *obj;

@@ -594,13 +594,13 @@ static acpi_status AMW0_set_capabilities
 	if (ACPI_FAILURE(status))
 		return status;
 
-	obj = (union acpi_object *) out.pointer;
+	obj = out.pointer;
 	if (obj && obj->type == ACPI_TYPE_BUFFER &&
 	obj->buffer.length == sizeof(struct wmab_ret)) {
 		ret = *((struct wmab_ret *) obj->buffer.pointer);
 	} else {
-		kfree(out.pointer);
-		return AE_ERROR;
+		status = AE_ERROR;
+		goto out;
 	}
 
 	if (ret.eax & 0x1)

@@ -614,25 +614,21 @@ static acpi_status AMW0_set_capabilities
 	 * But we need to kfree(out.pointer) if next wmab_execute fail.
 	 */
 	status = wmab_execute(&args, &out);
-	if (ACPI_FAILURE(status)) {
-		kfree(out.pointer);
-		return status;
-	}
+	if (ACPI_FAILURE(status))
+		goto out;
 
 	obj = (union acpi_object *) out.pointer;
 	if (obj && obj->type == ACPI_TYPE_BUFFER
 	&& obj->buffer.length == sizeof(struct wmab_ret)) {
 		ret = *((struct wmab_ret *) obj->buffer.pointer);
 	} else {
-		kfree(out.pointer);
-		return AE_ERROR;
+		status = AE_ERROR;
+		goto out;
 	}
 
 	if (ret.eax & 0x1)
 		interface->capability |= ACER_CAP_BLUETOOTH;
 
-	kfree(out.pointer);
-
 	/*
 	 * This appears to be safe to enable, since all Wistron based laptops
 	 * appear to use the same EC register for brightness, even if they

@@ -641,7 +637,10 @@ static acpi_status AMW0_set_capabilities
 	if (quirks->brightness >= 0)
 		interface->capability |= ACER_CAP_BRIGHTNESS;
 
-	return AE_OK;
+	status = AE_OK;
+out:
+	kfree(out.pointer);
+	return status;
 }
 
 static struct wmi_interface AMW0_interface = {

Axel Lin

author Acked-by

2010-07-13 02:14 UTC #3 lore raw

2010/7/13 Andrew Morton <[email protected]>:

Quoted 74 lines · On Fri, 09 Jul 2010 12:37:36 +0800 Axel Lin <[email protected]> wrote:

Quoted 53 lines
When acpi_evaluate_object() is passed ACPI_ALLOCATE_BUFFER, the caller must kfree the returned buffer if AE_OK is returned.
Call Trace:
wmab_execute
-> wmi_evaluate_method
-> acpi_evaluate_object
Thus if callers of wmab_execute() pass ACPI_ALLOCATE_BUFFER, the return buffer must be kfreed if wmab_execute return AE_OK.
Signed-off-by Axel Lin <[email protected]>
---
drivers/platform/x86/acer-wmi.c | 11 ++++++++++-
 1 files changed, 10 insertions(+), 1 deletions(-)
drivers/platform/x86/acer-wmi.c +9 -1
index 1ea6c43..3f44446 100644
@@ -555,6 +555,7 @@ static acpi_status AMW0_find_mailled(void)
       obj->buffer.length == sizeof(struct wmab_ret)) {
               ret = *((struct wmab_ret *) obj->buffer.pointer);
       } else {
+             kfree(out.pointer);
               return AE_ERROR;
       }
 
@@ -598,6 +599,7 @@ static acpi_status AMW0_set_capabilities(void)
       obj->buffer.length == sizeof(struct wmab_ret)) {
               ret = *((struct wmab_ret *) obj->buffer.pointer);
       } else {
+             kfree(out.pointer);
               return AE_ERROR;
       }
 
@@ -607,15 +609,22 @@ static acpi_status AMW0_set_capabilities(void)
       args.ebx = 2 << 8;
       args.ebx |= ACER_AMW0_BLUETOOTH_MASK;
 
+     /*
+      * It's ok to use existing buffer for next wmab_execute call.
+      * But we need to kfree(out.pointer) if next wmab_execute fail.
+      */
       status = wmab_execute(&args, &out);
-     if (ACPI_FAILURE(status))
+     if (ACPI_FAILURE(status)) {
+             kfree(out.pointer);
               return status;
+     }
 
       obj = (union acpi_object *) out.pointer;
Quoted 7 lines
if (obj && obj->type == ACPI_TYPE_BUFFER
&& obj->buffer.length == sizeof(struct wmab_ret)) { ret = *((struct wmab_ret *) obj->buffer.pointer); } else {
+ kfree(out.pointer);
return AE_ERROR;
}
I think it's best to remove the multiple-return-points approach in favour of the "goto single return point which undoes things" approach. that way we reduce the risk of later introducing more leaks.
Please review:
From: Andrew Morton <[email protected]>
avoid multiple return points
remove unneeded cast
remove unneeded initialisation of `status'

Quoted 6 lines

Cc Alan Jenkins <[email protected]>
Cc Axel Lin <[email protected]>
Cc Carlos Corbacho <[email protected]>
Cc Matthew Garrett <[email protected]>
Cc Thomas Renninger <[email protected]>
Signed-off-by Andrew Morton <[email protected]>

I'm not the author, but since I'm in the CC list and it looks good to me.

Acked-by Axel Lin <[email protected]>

Quoted 79 lines

---
drivers/platform/x86/acer-wmi.c | 25 ++++++++++++-------------
 1 file changed, 12 insertions(+), 13 deletions(-)
diff -puN drivers/platform/x86/acer-wmi.c~acer-wmi-fix-memory-leaks-in-wmab_execute-error-path-v2-fix drivers/platform/x86/acer-wmi.c
drivers/platform/x86/acer-wmi.c renamed from drivers/platform/x86/acer-wmi.c~acer-wmi-fix-memory-leaks-in-wmab_execute-error-path-v2-fix +2 -2
@@ -571,7 +571,7 @@ static acpi_status AMW0_set_capabilities
  {
        struct wmab_args args;
        struct wmab_ret ret;
-       acpi_status status = AE_OK;
+       acpi_status status;
        struct acpi_buffer out = { ACPI_ALLOCATE_BUFFER, NULL };
        union acpi_object *obj;
 
@@ -594,13 +594,13 @@ static acpi_status AMW0_set_capabilities
        if (ACPI_FAILURE(status))
                return status;
 
-       obj = (union acpi_object *) out.pointer;
+       obj = out.pointer;
if (obj && obj->type == ACPI_TYPE_BUFFER && obj->buffer.length == sizeof(struct wmab_ret)) { ret = *((struct wmab_ret *) obj->buffer.pointer); } else {
- kfree(out.pointer);
- return AE_ERROR;
+ status = AE_ERROR;
+ goto out;
}
if (ret.eax & 0x1)
drivers/platform/x86/acer-wmi.c renamed from drivers/platform/x86/acer-wmi.c~acer-wmi-fix-memory-leaks-in-wmab_execute-error-path-v2-fix +2 -4
@@ -614,25 +614,21 @@ static acpi_status AMW0_set_capabilities
         * But we need to kfree(out.pointer) if next wmab_execute fail.
         */
        status = wmab_execute(&args, &out);
-       if (ACPI_FAILURE(status)) {
-               kfree(out.pointer);
-               return status;
-       }
+       if (ACPI_FAILURE(status))
+               goto out;
 
        obj = (union acpi_object *) out.pointer;
if (obj && obj->type == ACPI_TYPE_BUFFER
&& obj->buffer.length == sizeof(struct wmab_ret)) { ret = *((struct wmab_ret *) obj->buffer.pointer); } else {
- kfree(out.pointer);
- return AE_ERROR;
+ status = AE_ERROR;
+ goto out;
}
if (ret.eax & 0x1)
interface->capability |= ACER_CAP_BLUETOOTH;
- kfree(out.pointer);
-
/*
* This appears to be safe to enable, since all Wistron based laptops
* appear to use the same EC register for brightness, even if they
drivers/platform/x86/acer-wmi.c renamed from drivers/platform/x86/acer-wmi.c~acer-wmi-fix-memory-leaks-in-wmab_execute-error-path-v2-fix +4 -1
@@ -641,7 +637,10 @@ static acpi_status AMW0_set_capabilities
        if (quirks->brightness >= 0)
                interface->capability |= ACER_CAP_BRIGHTNESS;
 
-       return AE_OK;
+       status = AE_OK;
+out:
+       kfree(out.pointer);
+       return status;
  }
 
  static struct wmi_interface AMW0_interface = {
_