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Message-ID: <AANLkTinM51K1s9dMqcmqZebF-x_bOK0OlKADkparP-Ek@mail.gmail.com>
Date: Tue, 13 Jul 2010 10:14:41 +0800
From: Axel Lin <axel.lin@...il.com>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: linux-kernel <linux-kernel@...r.kernel.org>,
Carlos Corbacho <carlos@...angeworlds.co.uk>,
Matthew Garrett <mjg@...hat.com>,
Thomas Renninger <trenn@...e.de>,
Alan Jenkins <alan-jenkins@...fmail.co.uk>,
platform-driver-x86@...r.kernel.org
Subject: Re: [PATCH v2] acer-wmi: fix memory leaks in wmab_execute error path
2010/7/13 Andrew Morton <akpm@...ux-foundation.org>:
> On Fri, 09 Jul 2010 12:37:36 +0800 Axel Lin <axel.lin@...il.com> 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 <axel.lin@...il.com>
>> ---
>> drivers/platform/x86/acer-wmi.c | 11 ++++++++++-
>> 1 files changed, 10 insertions(+), 1 deletions(-)
>>
>> diff --git a/drivers/platform/x86/acer-wmi.c b/drivers/platform/x86/acer-wmi.c
>> index 1ea6c43..3f44446 100644
>> --- a/drivers/platform/x86/acer-wmi.c
>> +++ b/drivers/platform/x86/acer-wmi.c
>> @@ -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;
>> }
>
> 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 <akpm@...ux-foundation.org>
>
> avoid multiple return points
> remove unneeded cast
> remove unneeded initialisation of `status'
>
> Cc: Alan Jenkins <alan-jenkins@...fmail.co.uk>
> Cc: Axel Lin <axel.lin@...il.com>
> Cc: Carlos Corbacho <carlos@...angeworlds.co.uk>
> Cc: Matthew Garrett <mjg@...hat.com>
> Cc: Thomas Renninger <trenn@...e.de>
> Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
I'm not the author, but since I'm in the CC list and it looks good to me.
Acked-by: Axel Lin <axel.lin@...il.com>
> ---
>
> 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
> --- a/drivers/platform/x86/acer-wmi.c~acer-wmi-fix-memory-leaks-in-wmab_execute-error-path-v2-fix
> +++ a/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 = {
> _
>
>
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