Re: [PATCH v5 4/5] misc: fastrpc: Allocate entire reserved memory for Audio PD in probe

[Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>]

On Fri, May 15, 2026 at 08:42:16PM +0800, Jianping Li wrote:
> Allocating and freeing Audio PD memory from userspace is unsafe because
> the kernel cannot reliably determine when the DSP has finished using the
> memory. Userspace may free buffers while they are still in use by the DSP,
> and remote free requests cannot be safely trusted.
> 
> Allocate the entire Audio PD reserved-memory region upfront during rpmsg
> probe and tie its lifetime to the rpmsg channel. This avoids userspace-
> controlled alloc/free and ensures memory is reclaimed only when the DSP
> shuts down.

So, is this a bugfix or not? Is it possible to make the kernel misbehave
without this patch being applied?

> 
> Signed-off-by: Jianping Li <jianping.li@oss.qualcomm.com>
> ---
>  drivers/misc/fastrpc.c | 107 +++++++++++++++++++----------------------
>  1 file changed, 49 insertions(+), 58 deletions(-)
> 

-- 
With best wishes
Dmitry