[PATCH 2/2] misc: fastrpc: Allocate entire reserved memory for Audio PD in probe

[Srinivas Kandagatla]

From: Jianping Li <jianping.li@xxxxxxxxxxxxxxxx>

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>
Link: https://lore.kernel.org/all/20260814101955.234238-1-jianping.li@xxxxxxxxxxxxxxxx/
Signed-off-by: Srinivas Kandagatla <srini@xxxxxxxxxx>
---
 drivers/misc/fastrpc.c | 188 ++++++++++++++++++++++-------------------
 1 file changed, 101 insertions(+), 87 deletions(-)

diff --git a/drivers/misc/fastrpc.c b/drivers/misc/fastrpc.c
index 4a18081845d9..9310ef1cb4a6 100644
--- a/drivers/misc/fastrpc.c
+++ b/drivers/misc/fastrpc.c
@@ -70,8 +70,6 @@
 #define ADSP_MMAP_HEAP_ADDR  4
 /* MAP static DMA buffer on DSP User PD */
 #define ADSP_MMAP_DMA_BUFFER  6
-/* Add memory to static PD pool protection thru hypervisor */
-#define ADSP_MMAP_REMOTE_HEAP_ADDR  8
 /* Add memory to userPD pool, for user heap */
 #define ADSP_MMAP_ADD_PAGES 0x1000
 /* Add memory to userPD pool, for LLC heap */
@@ -314,10 +312,14 @@ 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;
+	/* Audio PD reserved remote heap region */
+	phys_addr_t remote_heap_addr;
+	u64 remote_heap_size;
 	u32 dsp_attributes[FASTRPC_MAX_DSP_ATTRIBUTES];
 	struct fastrpc_device *secure_fdevice;
 	struct fastrpc_device *fdevice;
-	struct fastrpc_buf *remote_heap;
 	struct list_head invoke_interrupted_mmaps;
 	bool secure;
 	bool unsigned_support;
@@ -1454,15 +1456,24 @@ 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;
+
+	if (!cctx->remote_heap_addr || !cctx->remote_heap_size) {
+		err = -ENOMEM;
+		dev_err(fl->sctx->dev,
+			"remote heap memory region is not added\n");
+		return err;
+	}
 
 	args = kzalloc_objs(*args, FASTRPC_CREATE_STATIC_PROCESS_NARGS);
 	if (!args)
@@ -1486,31 +1497,6 @@ 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;
 
@@ -1522,8 +1508,25 @@ 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_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);
@@ -1541,27 +1544,11 @@ 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);
@@ -2090,7 +2077,7 @@ static int fastrpc_req_mmap(struct fastrpc_user *fl, char __user *argp)
 	if (copy_from_user(&req, argp, sizeof(req)))
 		return -EFAULT;
 
-	if (req.flags != ADSP_MMAP_ADD_PAGES && req.flags != ADSP_MMAP_REMOTE_HEAP_ADDR) {
+	if (req.flags != ADSP_MMAP_ADD_PAGES) {
 		dev_err(dev, "flag not supported 0x%x\n", req.flags);
 
 		return -EINVAL;
@@ -2101,10 +2088,7 @@ static int fastrpc_req_mmap(struct fastrpc_user *fl, char __user *argp)
 		return -EINVAL;
 	}
 
-	if (req.flags == ADSP_MMAP_REMOTE_HEAP_ADDR)
-		err = fastrpc_remote_heap_alloc(fl, dev, req.size, &buf);
-	else
-		err = fastrpc_buf_alloc(fl, dev, req.size, &buf);
+	err = fastrpc_buf_alloc(fl, dev, req.size, &buf);
 
 	if (err) {
 		dev_err(dev, "failed to allocate buffer\n");
@@ -2143,20 +2127,6 @@ static int fastrpc_req_mmap(struct fastrpc_user *fl, char __user *argp)
 	/* let the client know the address to use */
 	req.vaddrout = rsp_msg.vaddr;
 
-	/* Add memory to static PD pool, protection thru hypervisor */
-	if (req.flags == ADSP_MMAP_REMOTE_HEAP_ADDR && fl->cctx->vmcount) {
-		u64 src_perms = BIT(QCOM_SCM_VMID_HLOS);
-
-		err = qcom_scm_assign_mem(buf->dma_addr, (u64)buf->size,
-			&src_perms, fl->cctx->vmperms, fl->cctx->vmcount);
-		if (err) {
-			dev_err(fl->sctx->dev,
-				"Failed to assign memory dma_addr %pad size 0x%llx err %d",
-				&buf->dma_addr, buf->size, err);
-			goto err_assign;
-		}
-	}
-
 	spin_lock(&fl->lock);
 	list_add_tail(&buf->node, &fl->mmaps);
 	spin_unlock(&fl->lock);
@@ -2537,6 +2507,45 @@ static const struct of_device_id fastrpc_poll_supported_machines[] __maybe_unuse
 	{},
 };
 
+static int fastrpc_init_reserved_mem(struct fastrpc_channel_ctx *cctx,
+				     struct device *rdev, u32 domain_id)
+{
+	struct resource res;
+	u64 src_perms;
+	int err;
+
+	/* Only SDSP and ADSP domains use a reserved remote heap region */
+	if (domain_id != SDSP_DOMAIN_ID && domain_id != ADSP_DOMAIN_ID)
+		return 0;
+
+	err = of_reserved_mem_region_to_resource(rdev->of_node, 0, &res);
+	if (err) {
+		/*
+		 * The reserved-memory region is optional at probe time. For
+		 * the Audio PD (ADSP) domain its absence is validated later in
+		 * fastrpc_init_create_static_process(), so keep probing here.
+		 */
+		return 0;
+	}
+
+	/*
+	 * Audio PD (ADSP) is a static PD: cache the region so its lifetime
+	 * is tied to the rpmsg channel instead of being controlled by
+	 * userspace.
+	 */
+	if (domain_id == ADSP_DOMAIN_ID) {
+		cctx->remote_heap_addr = res.start;
+		cctx->remote_heap_size = resource_size(&res);
+	}
+
+	if (!cctx->vmcount)
+		return 0;
+
+	src_perms = BIT(QCOM_SCM_VMID_HLOS);
+	return qcom_scm_assign_mem(res.start, resource_size(&res), &src_perms,
+				  cctx->vmperms, cctx->vmcount);
+}
+
 static int fastrpc_rpmsg_probe(struct rpmsg_device *rpdev)
 {
 	struct device *rdev = &rpdev->dev;
@@ -2584,21 +2593,9 @@ static int fastrpc_rpmsg_probe(struct rpmsg_device *rpdev)
 		}
 	}
 
-	if (domain_id == SDSP_DOMAIN_ID) {
-		struct resource res;
-		u64 src_perms;
-
-		err = of_reserved_mem_region_to_resource(rdev->of_node, 0, &res);
-		if (!err) {
-			src_perms = BIT(QCOM_SCM_VMID_HLOS);
-
-			err = qcom_scm_assign_mem(res.start, resource_size(&res), &src_perms,
-				    data->vmperms, data->vmcount);
-			if (err)
-				goto err_free_data;
-		}
-
-	}
+	err = fastrpc_init_reserved_mem(data, rdev, domain_id);
+	if (err)
+		goto err_free_data;
 
 	secure_dsp = !(of_property_read_bool(rdev->of_node, "qcom,non-secure-domain"));
 	data->secure = secure_dsp;
@@ -2698,8 +2695,25 @@ 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_size && cctx->vmcount) {
+		u64 src_perms = 0;
+		int err, i;
+		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_addr,
+					  cctx->remote_heap_size, &src_perms,
+					  &dst_perms, 1);
+		if (err)
+			dev_err(&rpdev->dev,
+				"Failed to assign memory back to HLOS: addr %pa size %#llx err %d\n",
+				&cctx->remote_heap_addr, cctx->remote_heap_size, err);
+	}
 
 	of_platform_depopulate(&rpdev->dev);
 
-- 
2.53.0