2021-05-24 17:38:08

by Hyeonggon Yoo

Subject: [PATCH] ALSA: line6: Improve poor error handling in line6_init_cap_control

line6_init_cap_control doesn't free resources properly when allocations
like kmalloc, usb_alloc_urb fails. It can cause memory leak when some
allocations succeed, and then an error occurs.

This patch makes line6_init_cap_control to properly free the resources,
freeing previously allocated resources when there's an error.

Signed-off-by: Hyeonggon Yoo <[email protected]>
---
sound/usb/line6/driver.c | 36 +++++++++++++++++++++++++++---------
1 file changed, 27 insertions(+), 9 deletions(-)

diff --git a/sound/usb/line6/driver.c b/sound/usb/line6/driver.c
index 9602929b7de9..6991cb855023 100644
--- a/sound/usb/line6/driver.c
+++ b/sound/usb/line6/driver.c
@@ -688,34 +688,52 @@ static int line6_init_cap_control(struct usb_line6 *line6)

/* initialize USB buffers: */
line6->buffer_listen = kmalloc(LINE6_BUFSIZE_LISTEN, GFP_KERNEL);
- if (!line6->buffer_listen)
- return -ENOMEM;
+ if (!line6->buffer_listen) {
+ ret = -ENOMEM;
+ goto fail_ret;
+ }

line6->urb_listen = usb_alloc_urb(0, GFP_KERNEL);
- if (!line6->urb_listen)
- return -ENOMEM;
+ if (!line6->urb_listen) {
+ ret = -ENOMEM;
+ goto fail1;
+ }

if (line6->properties->capabilities & LINE6_CAP_CONTROL_MIDI) {
line6->buffer_message = kmalloc(LINE6_MIDI_MESSAGE_MAXLEN, GFP_KERNEL);
- if (!line6->buffer_message)
- return -ENOMEM;
+ if (!line6->buffer_message) {
+ ret = -ENOMEM;
+ goto fail2;
+ }

ret = line6_init_midi(line6);
if (ret < 0)
- return ret;
+ goto fail3;
} else {
ret = line6_hwdep_init(line6);
if (ret < 0)
- return ret;
+ goto fail2;
}

ret = line6_start_listen(line6);
if (ret < 0) {
dev_err(line6->ifcdev, "cannot start listening: %d\n", ret);
- return ret;
+ if (line6->properties->capabilities & LINE6_CAP_CONTROL_MIDI)
+ goto fail3;
+ else
+ goto fail2;
}

return 0;
+
+fail3:
+ kfree(line6->buffer_message);
+fail2:
+ usb_free_urb(line6->urb_listen);
+fail1:
+ kfree(line6->buffer_listen);
+fail_ret:
+ return ret;
}

static void line6_startup_work(struct work_struct *work)
--
2.25.1

2021-05-24 17:41:01

by Hyeonggon Yoo

Subject: Re: [PATCH] ALSA: line6: Improve poor error handling in line6_init_cap_control

added an error handling code. It builds well,
but I don't have the device. So please review it (and test if you have one)

if you think I can improve something, please tell me.
I'll send v2.

Thanks,
Hyeonggon

2021-05-25 08:10:19

by Takashi Iwai

Subject: Re: [PATCH] ALSA: line6: Improve poor error handling in line6_init_cap_control

On Mon, 24 May 2021 19:36:44 +0200,
Hyeonggon Yoo wrote:
>
> line6_init_cap_control doesn't free resources properly when allocations
> like kmalloc, usb_alloc_urb fails. It can cause memory leak when some
> allocations succeed, and then an error occurs.
>
> This patch makes line6_init_cap_control to properly free the resources,
> freeing previously allocated resources when there's an error.
>
> Signed-off-by: Hyeonggon Yoo <[email protected]>
> ---
> sound/usb/line6/driver.c | 36 +++++++++++++++++++++++++++---------
> 1 file changed, 27 insertions(+), 9 deletions(-)
>
> diff --git a/sound/usb/line6/driver.c b/sound/usb/line6/driver.c
> index 9602929b7de9..6991cb855023 100644
> --- a/sound/usb/line6/driver.c
> +++ b/sound/usb/line6/driver.c
> @@ -688,34 +688,52 @@ static int line6_init_cap_control(struct usb_line6 *line6)
>
> /* initialize USB buffers: */
> line6->buffer_listen = kmalloc(LINE6_BUFSIZE_LISTEN, GFP_KERNEL);
> - if (!line6->buffer_listen)
> - return -ENOMEM;
> + if (!line6->buffer_listen) {
> + ret = -ENOMEM;
> + goto fail_ret;
> + }
>
> line6->urb_listen = usb_alloc_urb(0, GFP_KERNEL);
> - if (!line6->urb_listen)
> - return -ENOMEM;
> + if (!line6->urb_listen) {
> + ret = -ENOMEM;
> + goto fail1;
> + }
>
> if (line6->properties->capabilities & LINE6_CAP_CONTROL_MIDI) {
> line6->buffer_message = kmalloc(LINE6_MIDI_MESSAGE_MAXLEN, GFP_KERNEL);
> - if (!line6->buffer_message)
> - return -ENOMEM;
> + if (!line6->buffer_message) {
> + ret = -ENOMEM;
> + goto fail2;
> + }
>
> ret = line6_init_midi(line6);
> if (ret < 0)
> - return ret;
> + goto fail3;
> } else {
> ret = line6_hwdep_init(line6);
> if (ret < 0)
> - return ret;
> + goto fail2;
> }
>
> ret = line6_start_listen(line6);
> if (ret < 0) {
> dev_err(line6->ifcdev, "cannot start listening: %d\n", ret);
> - return ret;
> + if (line6->properties->capabilities & LINE6_CAP_CONTROL_MIDI)
> + goto fail3;
> + else
> + goto fail2;
> }
>
> return 0;
> +
> +fail3:
> + kfree(line6->buffer_message);
> +fail2:
> + usb_free_urb(line6->urb_listen);
> +fail1:
> + kfree(line6->buffer_listen);
> +fail_ret:
> + return ret;
> }

Those resources are freed in the common destructor of the card
instance, line6_destruct(), at disconnect callback, so it's redundant
to release them here; even worse, since you haven't re-initialize with
NULL, this change would lead to double-free.


thanks,

Takashi

2021-05-25 10:05:03

by Hyeonggon Yoo

Subject: Re: [PATCH] ALSA: line6: Improve poor error handling in line6_init_cap_control

On Tue, May 25, 2021 at 09:05:13AM +0200, Takashi Iwai wrote:
> Those resources are freed in the common destructor of the card
> instance, line6_destruct(),

Oh my god, I missed line6_destruct.

> at disconnect callback, so it's redundant
> to release them here; even worse, since you haven't re-initialize with
> NULL, this change would lead to double-free.

Yes then it can cause double-free..

>
>
> thanks,
>
> Takashi

I made a mistake, I'm so sorry to take your time...

Thanks,
Hyeonggon