Re: [PATCH v3] media: meson: vdec: Fix memory leak in error path of vdec_open

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 3 potential issue(s) to consider:

Pre-existing issues:
- [Critical] The `sess->esparser_queue_work` work item is not canceled before freeing the session context, leading to a potential Use-After-Free vulnerability.
- [High] The patch attempts to fix a memory leak reported by kmemleak, but misdiagnoses the root cause and leaves the primary memory leak (the V4L2 control handler) unresolved.
- [High] The driver does not verify if `kthread_run()` returns an `ERR_PTR`, leading to a kernel panic when `kthread_stop()` is called.
--

commit acccc4fc02fe5e1be0c545d1722179667c078475
Author: Anand Moon <linux.amoon@gmail.com>

media: meson: vdec: Fix memory leak in error path of vdec_open

This commit introduces a proper err_m2m_ctx_release label in the
vdec_open function. It ensures v4l2_m2m_ctx_release is called when
vdec_init_ctrls fails, preventing a memory leak of the m2m context.

> diff --git a/drivers/staging/media/meson/vdec/vdec.c b/drivers/staging/media/meson/vdec/vdec.c
> index 4b77ec1af5a76..a039d925c0fe5 100644
> --- a/drivers/staging/media/meson/vdec/vdec.c
> +++ b/drivers/staging/media/meson/vdec/vdec.c
> @@ -889,7 +889,7 @@ static int vdec_open(struct file *file)
>  
>  	ret = vdec_init_ctrls(sess);
>  	if (ret)
> -		goto err_m2m_release;
> +		goto err_m2m_ctx_release;

[Severity: High]
This isn't a bug introduced by this patch, but does vdec_close() properly
free the v4l2 control handler memory allocated by vdec_init_ctrls() here?

While this patch fixes the m2m context leak on the error path, if
vdec_close() fails to call v4l2_ctrl_handler_free(&sess->ctrl_handler),
could this control handler memory still leak on every successful open and
close cycle?

[Severity: Critical]
This is a pre-existing issue, but is the sess->esparser_queue_work item
canceled before freeing the session context?

The work item is initialized in vdec_open():

vdec_open() {
    ...
    INIT_WORK(&sess->esparser_queue_work, esparser_queue_all_src);
    ...
}

If vdec_close() calls kfree(sess) without first stopping or synchronizing
with this background work via cancel_work_sync(), could a concurrently
running esparser_queue_all_src() dereference the freed sess structure and
trigger a use-after-free?

[Severity: High]
This isn't a bug introduced by this patch, but does the driver verify if
kthread_run() returns an ERR_PTR when starting the recycle thread?

If thread creation fails in vdec_start_streaming() and returns an ERR_PTR,
could a later call to kthread_stop(sess->recycle_thread) in
vdec_stop_streaming() attempt to dereference that ERR_PTR and cause a
kernel panic?

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260520044046.7553-1-linux.amoon@gmail.com?part=1

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