[PATCH] ALSA: usb-audio: qcom: Check offload mapping failures

[PATCH] ALSA: usb-audio: qcom: Check offload mapping failures

[Cássio Gabriel]

uaudio_transfer_buffer_setup() calls dma_get_sgtable() and then passes
the sg_table to uaudio_iommu_map_xfer_buf() without checking whether sg
table construction succeeded. If dma_get_sgtable() fails, the sg_table
contents are not valid.

uaudio_iommu_map_pa() also ignores iommu_map() failures for the event and
transfer rings and still returns the allocated IOVA to the QMI response.
That can expose an unmapped IOVA to the audio DSP. For transfer rings,
the failed mapping also leaves the IOVA allocator state marked in use.

Check both operations. Free the coherent transfer buffer when sg table
construction fails, free the sg table when transfer-buffer IOMMU mapping
fails, and release the transfer-ring IOVA if iommu_map() fails. Also
return the existing event-ring IOVA when the event ring is already mapped,
matching the pre-split helper behavior.

Fixes: 326bbc348298 ("ALSA: usb-audio: qcom: Introduce QC USB SND offloading support")
Fixes: 44499ecb4f28 ("ALSA: usb: qcom: Fix false-positive address space check")
Cc: stable@vger.kernel.org
Signed-off-by: Cássio Gabriel <cassiogabrielcontato@gmail.com>
---
 sound/usb/qcom/qc_audio_offload.c | 31 +++++++++++++++++++++++++------
 1 file changed, 25 insertions(+), 6 deletions(-)

diff --git a/sound/usb/qcom/qc_audio_offload.c b/sound/usb/qcom/qc_audio_offload.c
index 5f993b88448c..a0009503b2c5 100644
--- a/sound/usb/qcom/qc_audio_offload.c
+++ b/sound/usb/qcom/qc_audio_offload.c
@@ -565,6 +565,7 @@ static unsigned long uaudio_iommu_map_pa(enum mem_type mtype, bool dma_coherent,
 	unsigned long iova = 0;
 	bool map = true;
 	int prot = uaudio_iommu_map_prot(dma_coherent);
+	int ret;
 
 	switch (mtype) {
 	case MEM_EVENT_RING:
@@ -582,10 +583,24 @@ static unsigned long uaudio_iommu_map_pa(enum mem_type mtype, bool dma_coherent,
 		dev_err(uaudio_qdev->data->dev, "unknown mem type %d\n", mtype);
 	}
 
-	if (!iova || !map)
+	if (!iova)
 		return 0;
 
-	iommu_map(uaudio_qdev->data->domain, iova, pa, size, prot, GFP_KERNEL);
+	if (!map)
+		return iova;
+
+	ret = iommu_map(uaudio_qdev->data->domain, iova, pa, size, prot,
+			GFP_KERNEL);
+	if (ret) {
+		dev_err(uaudio_qdev->data->dev,
+			"failed to map %zu bytes at iova 0x%08lx: %d\n",
+			size, iova, ret);
+		if (mtype == MEM_XFER_RING)
+			uaudio_put_iova(iova, size,
+					&uaudio_qdev->xfer_ring_list,
+					&uaudio_qdev->xfer_ring_iova_size);
+		return 0;
+	}
 
 	return iova;
 }
@@ -1054,15 +1069,17 @@ static int uaudio_transfer_buffer_setup(struct snd_usb_substream *subs,
 	if (!xfer_buf)
 		return -ENOMEM;
 
-	dma_get_sgtable(subs->dev->bus->sysdev, &xfer_buf_sgt, xfer_buf,
-			xfer_buf_dma, len);
+	ret = dma_get_sgtable(subs->dev->bus->sysdev, &xfer_buf_sgt, xfer_buf,
+			      xfer_buf_dma, len);
+	if (ret)
+		goto free_xfer_buf;
 
 	/* map the physical buffer into sysdev as well */
 	xfer_buf_dma_sysdev = uaudio_iommu_map_xfer_buf(dma_coherent,
 							len, &xfer_buf_sgt);
 	if (!xfer_buf_dma_sysdev) {
 		ret = -ENOMEM;
-		goto unmap_sync;
+		goto free_sgt;
 	}
 
 	mem_info->dma = xfer_buf_dma;
@@ -1073,7 +1090,9 @@ static int uaudio_transfer_buffer_setup(struct snd_usb_substream *subs,
 
 	return 0;
 
-unmap_sync:
+free_sgt:
+	sg_free_table(&xfer_buf_sgt);
+free_xfer_buf:
 	usb_free_coherent(subs->dev, len, xfer_buf, xfer_buf_dma);
 
 	return ret;

---
base-commit: ab4a88fdef2813446e3af179a708d024622ff4fa
change-id: 20260422-alsa-usb-qcom-offload-map-errors-ddbb6dbf758a

Best regards,
--  
Cássio Gabriel <cassiogabrielcontato@gmail.com>