Re: [PATCH v10] misc: fastrpc: Allocate entire reserved memory for Audio PD in probe

[Ekansh Gupta <ekansh.gupta@oss.qualcomm.com>]

On 16-07-2026 15:28, 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.
> 
> Add explicit validation for remote_heap presence and size before sending
> the memory to DSP, and fail early if the reserved-memory region is
> missing or incomplete.
Can you also drop ADSP_MMAP_REMOTE_HEAP_ADDR support from
fastrpc_req_mmap as we don't intend user process to grow/shrink audio
PD's remote heap.>
> Fixes: 0871561055e66 ("misc: fastrpc: Add support for audiopd")
> Cc: stable@kernel.org
> Signed-off-by: Jianping Li <jianping.li@oss.qualcomm.com>
> 
> Patch [v9]: https://lore.kernel.org/all/20260707061733.495-1-jianping.li@oss.qualcomm.com/
> 
> Changes in v10:
>  - Move Audio PD remote heap validation into
>    fastrpc_rpmsg_probe().
> 
>  - Treat Audio PD remote heap as a mandatory
>    resource and fail probe if the reserved
>    memory region is missing.
> 
> Changes in v9:
>  - Make sure fastrpc_init_create_static_process()
>    only sets audio_init_mem to false when the sent
>    address is actually invalid.
> ---
>  drivers/misc/fastrpc.c | 121 +++++++++++++++++++++++------------------
>  1 file changed, 69 insertions(+), 52 deletions(-)
> 
> diff --git a/drivers/misc/fastrpc.c b/drivers/misc/fastrpc.c
> index d86e79134c68..03f633028c00 100644
> --- a/drivers/misc/fastrpc.c
> +++ b/drivers/misc/fastrpc.c
> @@ -276,6 +276,8 @@ struct fastrpc_channel_ctx {
>  	struct kref refcount;
>  	/* Flag if dsp attributes are cached */
>  	bool valid_attributes;
> +	/* Flag if audio PD init mem was allocated */
> +	bool audio_init_mem;
>  	u32 dsp_attributes[FASTRPC_MAX_DSP_ATTRIBUTES];
>  	struct fastrpc_device *secure_fdevice;
>  	struct fastrpc_device *fdevice;
> @@ -1344,15 +1346,17 @@ static int fastrpc_init_create_static_process(struct fastrpc_user *fl,
>  	struct fastrpc_init_create_static init;
>  	struct fastrpc_invoke_args *args;
>  	struct fastrpc_phy_page pages[1];
> +	struct fastrpc_channel_ctx *cctx = fl->cctx;
>  	char *name;
>  	int err;
> -	bool scm_done = false;
>  	struct {
>  		int client_id;
>  		u32 namelen;
>  		u32 pageslen;
>  	} inbuf;
>  	u32 sc;
> +	unsigned long flags;
> +	bool sent_heap = false;
>  
>  	args = kzalloc_objs(*args, FASTRPC_CREATE_STATIC_PROCESS_NARGS);
>  	if (!args)
> @@ -1376,31 +1380,6 @@ static int fastrpc_init_create_static_process(struct fastrpc_user *fl,
>  	inbuf.client_id = fl->client_id;
>  	inbuf.namelen = init.namelen;
>  	inbuf.pageslen = 0;
> -	if (!fl->cctx->remote_heap) {
> -		err = fastrpc_remote_heap_alloc(fl, fl->sctx->dev, init.memlen,
> -						&fl->cctx->remote_heap);
> -		if (err)
> -			goto err_name;
> -
> -		/* Map if we have any heap VMIDs associated with this ADSP Static Process. */
> -		if (fl->cctx->vmcount) {
> -			u64 src_perms = BIT(QCOM_SCM_VMID_HLOS);
> -
> -			err = qcom_scm_assign_mem(fl->cctx->remote_heap->dma_addr,
> -							(u64)fl->cctx->remote_heap->size,
> -							&src_perms,
> -							fl->cctx->vmperms, fl->cctx->vmcount);
> -			if (err) {
> -				dev_err(fl->sctx->dev,
> -					"Failed to assign memory with dma_addr %pad size 0x%llx err %d\n",
> -					&fl->cctx->remote_heap->dma_addr,
> -					fl->cctx->remote_heap->size, err);
> -				goto err_map;
> -			}
> -			scm_done = true;
> -			inbuf.pageslen = 1;
> -		}
> -	}
>  
>  	fl->pd = USER_PD;
>  
> @@ -1412,8 +1391,25 @@ static int fastrpc_init_create_static_process(struct fastrpc_user *fl,
>  	args[1].length = inbuf.namelen;
>  	args[1].fd = -1;
>  
> -	pages[0].addr = fl->cctx->remote_heap->dma_addr;
> -	pages[0].size = fl->cctx->remote_heap->size;
> +	/*
> +	 * Audio PD is a static PD and retains the remote heap
> +	 * information across daemon restarts. Therefore only
> +	 * the first attach should provide heap information to
> +	 * DSP. Subsequent attaches reuse the previously
> +	 * initialized memory pool.
> +	 */
> +	spin_lock_irqsave(&cctx->lock, flags);
> +	if (!cctx->audio_init_mem) {
> +		pages[0].addr = cctx->remote_heap->dma_addr;
> +		pages[0].size = cctx->remote_heap->size;
> +		cctx->audio_init_mem = true;
> +		inbuf.pageslen = 1;
> +		sent_heap = true;
> +	} else {
> +		pages[0].addr = 0;
> +		pages[0].size = 0;
> +	}
> +	spin_unlock_irqrestore(&cctx->lock, flags);
>  
>  	args[2].ptr = (u64)(uintptr_t) pages;
>  	args[2].length = sizeof(*pages);
> @@ -1431,27 +1427,11 @@ static int fastrpc_init_create_static_process(struct fastrpc_user *fl,
>  
>  	return 0;
>  err_invoke:
> -	if (fl->cctx->vmcount && scm_done) {
> -		u64 src_perms = 0;
> -		struct qcom_scm_vmperm dst_perms;
> -		u32 i;
> -
> -		for (i = 0; i < fl->cctx->vmcount; i++)
> -			src_perms |= BIT(fl->cctx->vmperms[i].vmid);
> -
> -		dst_perms.vmid = QCOM_SCM_VMID_HLOS;
> -		dst_perms.perm = QCOM_SCM_PERM_RWX;
> -		err = qcom_scm_assign_mem(fl->cctx->remote_heap->dma_addr,
> -						(u64)fl->cctx->remote_heap->size,
> -						&src_perms, &dst_perms, 1);
> -		if (err)
> -			dev_err(fl->sctx->dev, "Failed to assign memory dma_addr %pad size 0x%llx err %d\n",
> -				&fl->cctx->remote_heap->dma_addr, fl->cctx->remote_heap->size, err);
> +	if (sent_heap) {
> +		spin_lock_irqsave(&cctx->lock, flags);
> +		cctx->audio_init_mem = false;
> +		spin_unlock_irqrestore(&cctx->lock, flags);
>  	}
> -err_map:
> -	fastrpc_buf_free(fl->cctx->remote_heap);
> -	fl->cctx->remote_heap = NULL;
> -err_name:
>  	kfree(name);
>  err:
>  	kfree(args);
> @@ -2418,12 +2398,29 @@ static int fastrpc_rpmsg_probe(struct rpmsg_device *rpdev)
>  		}
>  	}
>  
> -	if (domain_id == SDSP_DOMAIN_ID) {
> +	if (domain_id == SDSP_DOMAIN_ID || domain_id == ADSP_DOMAIN_ID) {
>  		struct resource res;
>  		u64 src_perms;
>  
>  		err = of_reserved_mem_region_to_resource(rdev->of_node, 0, &res);
> +
> +		if (err && domain_id == ADSP_DOMAIN_ID) {
> +			dev_err(rdev, "missing mandatory remote heap memory-region\n");
> +			goto err_free_data;
> +		}
> +
>  		if (!err) {
> +			if (domain_id == ADSP_DOMAIN_ID) {
> +				data->remote_heap =
> +					kzalloc_obj(*data->remote_heap);
> +				if (!data->remote_heap) {
> +					err = -ENOMEM;
> +					goto err_free_data;
> +				}
> +
> +				data->remote_heap->dma_addr = res.start;
> +				data->remote_heap->size = resource_size(&res);
other struct fastrpc_buf members are not initialized here. Either
initialize all or better just add remote_heap_addr and remote_heap_size
to fastrpc_channel_ctx structure.> +			}
>  			src_perms = BIT(QCOM_SCM_VMID_HLOS);
>  
>  			err = qcom_scm_assign_mem(res.start, resource_size(&res), &src_perms,
> @@ -2431,7 +2428,6 @@ static int fastrpc_rpmsg_probe(struct rpmsg_device *rpdev)
>  			if (err)
>  				goto err_free_data;
>  		}
> -
>  	}
>  
>  	secure_dsp = !(of_property_read_bool(rdev->of_node, "qcom,non-secure-domain"));
> @@ -2490,6 +2486,7 @@ static int fastrpc_rpmsg_probe(struct rpmsg_device *rpdev)
>  		misc_deregister(&data->secure_fdevice->miscdev);
>  
>  err_free_data:
> +	kfree(data->remote_heap);
>  	kfree(data);
>  	return err;
>  }
> @@ -2512,6 +2509,7 @@ static void fastrpc_rpmsg_remove(struct rpmsg_device *rpdev)
>  	struct fastrpc_buf *buf, *b;
>  	struct fastrpc_user *user;
>  	unsigned long flags;
> +	int err, i;
>  
>  	/* No invocations past this point */
>  	spin_lock_irqsave(&cctx->lock, flags);
> @@ -2529,8 +2527,27 @@ static void fastrpc_rpmsg_remove(struct rpmsg_device *rpdev)
>  	list_for_each_entry_safe(buf, b, &cctx->invoke_interrupted_mmaps, node)
>  		list_del(&buf->node);
>  
> -	if (cctx->remote_heap)
> -		fastrpc_buf_free(cctx->remote_heap);
> +	if (cctx->remote_heap && cctx->vmcount) {
> +		u64 src_perms = 0;
> +		struct qcom_scm_vmperm dst_perms;
> +
> +		for (i = 0; i < cctx->vmcount; i++)
> +			src_perms |= BIT(cctx->vmperms[i].vmid);
> +
> +		dst_perms.vmid = QCOM_SCM_VMID_HLOS;
> +		dst_perms.perm = QCOM_SCM_PERM_RWX;
> +
> +		err = qcom_scm_assign_mem(cctx->remote_heap->dma_addr,
> +					  cctx->remote_heap->size, &src_perms,
> +					  &dst_perms, 1);
> +		if (err)
> +			dev_err(&rpdev->dev,
> +				"Failed to assign memory back to HLOS: dma_addr %pad size %#llx err %d\n",
> +				&cctx->remote_heap->dma_addr, cctx->remote_heap->size, err);
> +	}
> +
> +	kfree(cctx->remote_heap);
> +	cctx->remote_heap = NULL;
>  
>  	of_platform_depopulate(&rpdev->dev);
>