Re: [PATCH v13] misc: fastrpc: Allocate entire reserved memory for Audio PD in probe

[Ekansh Gupta]

On 26-08-2026 09:08, 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.
> 
> Additionally, the current implementation allows userspace to repeatedly
> grow the Audio PD heap, but does not support shrinking it. This can lead
> to unbounded memory usage over time, effectively causing a memory leak.
> 
> Fix this by allocating the entire Audio PD reserved-memory region during
> rpmsg probe and tying its lifetime to the rpmsg channel. This removes
> userspace-controlled alloc/free and ensures that memory is reclaimed only
> when the DSP process is torn down.
> 
> The reserved-memory region is now mandatory for the Audio PD domain.
> Rather than failing rpmsg probe when it is missing, validate it in
> fastrpc_init_create_static_process() and reject only the static-process
> creation. This keeps the fastrpc device probing for all other domains
> even on a misconfigured device tree.
> 
> Fixes: 0871561055e66 ("misc: fastrpc: Add support for audiopd")
> Cc: stable@xxxxxxxxxx
> Signed-off-by: Jianping Li <jianping.li@xxxxxxxxxxxxxxxx>

Reviewed-by: Ekansh Gupta <ekansh.gupta@xxxxxxxxxxxxxxxx>