Re: [PATCH v9] misc: fastrpc: Allocate entire reserved memory for Audio PD in probe

[Jianping Li]

On 7/7/2026 3:01 PM, Ekansh Gupta wrote:

On 07-07-2026 11:47, 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.

Fixes: 0871561055e66 ("misc: fastrpc: Add support for audiopd")
Cc: sta...@kernel.org
Signed-off-by: Jianping Li <jianping...@oss.qualcomm.com>
---

Changes in vN and lore link to v(N-1) series would help here.>
drivers/misc/fastrpc.c | 119 +++++++++++++++++++++++------------------

Will add changelog and lore link in next version.

  1 file changed, 66 insertions(+), 53 deletions(-)

diff --git a/drivers/misc/fastrpc.c b/drivers/misc/fastrpc.c
index d86e79134c68..1ec37e6c68a2 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 +1346,24 @@ 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;
+
+       if (!cctx->remote_heap || !cctx->remote_heap->dma_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)
@@ -1376,31 +1387,6 @@ 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 +1398,24 @@ 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;
+       } 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 +1433,7 @@ 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);
-       }
-err_map:
-       fastrpc_buf_free(fl->cctx->remote_heap);
-       fl->cctx->remote_heap = NULL;
-err_name:
+       cctx->audio_init_mem = false;
        kfree(name);
  err:
        kfree(args);
@@ -2418,12 +2400,23 @@ 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) {
+                       if (domain_id == ADSP_DOMAIN_ID) {
+                               data->remote_heap =
+                                       kzalloc_obj(*data->remote_heap, 
GFP_KERNEL);

drop GFP_KERNEL from kzalloc_obj()> +                                if 
(!data->remote_heap) {

ACK,I'll drop GFP_KERNEL.

+                                       err = -ENOMEM;
+                                       goto err_free_data;
+                               }
+
+                               data->remote_heap->dma_addr = res.start;
+                               data->remote_heap->size = resource_size(&res);
+                       }
                        src_perms = BIT(QCOM_SCM_VMID_HLOS);

err = qcom_scm_assign_mem(res.start, resource_size(&res), &src_perms,

@@ -2431,7 +2424,6 @@ 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 +2482,7 @@ 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 +2505,7 @@ static void fastrpc_rpmsg_remove(struct rpmsg_device 
*rpdev)
        struct fastrpc_buf *buf, *b;
        struct fastrpc_user *user;
        unsigned long flags;
+       int err;

/* No invocations past this point */

        spin_lock_irqsave(&cctx->lock, flags);
@@ -2529,8 +2523,27 @@ 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 (u32 i = 0; i < cctx->vmcount; i++)

for the iterator use top-of-block declaration style for consistency> +          
     
src_perms |= BIT(cctx->vmperms[i].vmid);

Will fix.

+
+               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);