FAILED: patch "[PATCH] firmware: tee_bnxt: Release TEE shm, session, and context" failed to apply to 5.10-stable tree

The patch below does not apply to the 5.10-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 914ab19e471d8fb535ed50dff108b0a615f3c2d8 Mon Sep 17 00:00:00 2001
From: Allen Pais <[email protected]>
Date: Mon, 14 Jun 2021 17:33:17 -0500
Subject: [PATCH] firmware: tee_bnxt: Release TEE shm, session, and context
during kexec

Implement a .shutdown hook that will be called during a kexec operation so that the TEE shared memory, session, and context that were set up during .probe can be properly freed/closed.

Additionally, don't use dma-buf backed shared memory for the fw_shm_pool. dma-buf backed shared memory cannot be reliably freed and unregistered during a kexec operation even when tee_shm_free() is called on the shm from a .shutdown hook. The problem occurs because dma_buf_put() calls fput() which then uses task_work_add(), with the TWA_RESUME parameter, to queue tee_shm_release() to be called before the current task returns to user mode. However, the current task never returns to user mode before the kexec completes so the memory is never freed nor unregistered.

Use tee_shm_alloc_kernel_buf() to avoid dma-buf backed shared memory allocation so that tee_shm_free() can directly call tee_shm_release(). This will ensure that the shm can be freed and unregistered during a kexec operation.

index ed10da5313e8..a5bf4c3f6dc7 100644
@@ -212,10 +212,9 @@ static int tee_bnxt_fw_probe(struct device *dev)
 
 	pvt_data.dev = dev;
 
-	fw_shm_pool = tee_shm_alloc(pvt_data.ctx, MAX_SHM_MEM_SZ,
-				    TEE_SHM_MAPPED | TEE_SHM_DMA_BUF);
+	fw_shm_pool = tee_shm_alloc_kernel_buf(pvt_data.ctx, MAX_SHM_MEM_SZ);
 	if (IS_ERR(fw_shm_pool)) {
-		dev_err(pvt_data.dev, "tee_shm_alloc failed\n");
+		dev_err(pvt_data.dev, "tee_shm_alloc_kernel_buf failed\n");
 		err = PTR_ERR(fw_shm_pool);
 		goto out_sess;
 	}

@@ -242,6 +241,14 @@ static int tee_bnxt_fw_remove(struct device *dev)
 	return 0;
 }
 
+static void tee_bnxt_fw_shutdown(struct device *dev)
+{
+	tee_shm_free(pvt_data.fw_shm_pool);
+	tee_client_close_session(pvt_data.ctx, pvt_data.session_id);
+	tee_client_close_context(pvt_data.ctx);
+	pvt_data.ctx = NULL;
+}
+
 static const struct tee_client_device_id tee_bnxt_fw_id_table[] = {
 	{UUID_INIT(0x6272636D, 0x2019, 0x0716,
 		    0x42, 0x43, 0x4D, 0x5F, 0x53, 0x43, 0x48, 0x49)},

@@ -257,6 +264,7 @@ static struct tee_client_driver tee_bnxt_fw_driver = {
 		.bus		= &tee_bus_type,
 		.probe		= tee_bnxt_fw_probe,
 		.remove		= tee_bnxt_fw_remove,
+		.shutdown	= tee_bnxt_fw_shutdown,
 	},
 };
 

From: Allen Pais <[email protected]>

commit 914ab19e471d8fb535ed50dff108b0a615f3c2d8 upstream.

Implement a .shutdown hook that will be called during a kexec operation so that the TEE shared memory, session, and context that were set up during .probe can be properly freed/closed.

Additionally, don't use dma-buf backed shared memory for the fw_shm_pool. dma-buf backed shared memory cannot be reliably freed and unregistered during a kexec operation even when tee_shm_free() is called on the shm from a .shutdown hook. The problem occurs because dma_buf_put() calls fput() which then uses task_work_add(), with the TWA_RESUME parameter, to queue tee_shm_release() to be called before the current task returns to user mode. However, the current task never returns to user mode before the kexec completes so the memory is never freed nor unregistered.

Use tee_shm_alloc_kernel_buf() to avoid dma-buf backed shared memory allocation so that tee_shm_free() can directly call tee_shm_release(). This will ensure that the shm can be freed and unregistered during a kexec operation.

---

Hi Greg - Please include this backported patch in the 5.10-stable and 5.13-stable queues since the upstream commit couldn't be automatically backported. We've been using this backported version of the patch on top of 5.10.54 and it has received real world usage in production environments.

 drivers/firmware/broadcom/tee_bnxt_fw.c | 14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

index ed10da5313e8..a5bf4c3f6dc7 100644
@@ -212,10 +212,9 @@ static int tee_bnxt_fw_probe(struct device *dev)
 
 	pvt_data.dev = dev;
 
-	fw_shm_pool = tee_shm_alloc(pvt_data.ctx, MAX_SHM_MEM_SZ,
-				    TEE_SHM_MAPPED | TEE_SHM_DMA_BUF);
+	fw_shm_pool = tee_shm_alloc_kernel_buf(pvt_data.ctx, MAX_SHM_MEM_SZ);
 	if (IS_ERR(fw_shm_pool)) {
-		dev_err(pvt_data.dev, "tee_shm_alloc failed\n");
+		dev_err(pvt_data.dev, "tee_shm_alloc_kernel_buf failed\n");
 		err = PTR_ERR(fw_shm_pool);
 		goto out_sess;
 	}

@@ -242,6 +241,14 @@ static int tee_bnxt_fw_remove(struct device *dev)
 	return 0;
 }
 
+static void tee_bnxt_fw_shutdown(struct device *dev)
+{
+	tee_shm_free(pvt_data.fw_shm_pool);
+	tee_client_close_session(pvt_data.ctx, pvt_data.session_id);
+	tee_client_close_context(pvt_data.ctx);
+	pvt_data.ctx = NULL;
+}
+
 static const struct tee_client_device_id tee_bnxt_fw_id_table[] = {
 	{UUID_INIT(0x6272636D, 0x2019, 0x0716,
 		    0x42, 0x43, 0x4D, 0x5F, 0x53, 0x43, 0x48, 0x49)},

@@ -257,6 +264,7 @@ static struct tee_client_driver tee_bnxt_fw_driver = {
 		.bus		= &tee_bus_type,
 		.probe		= tee_bnxt_fw_probe,
 		.remove		= tee_bnxt_fw_remove,
+		.shutdown	= tee_bnxt_fw_shutdown,
 	},
 };
 

2.25.1