[PATCH v3 0/2] scsi: ufs: rpmb: Fix bus registration and device lifecycle

[PATCH v3 0/2] scsi: ufs: rpmb: Fix bus registration and device lifecycle

[Stanley Jhu]

This series fixes bus registration and device lifecycle defects in the
UFS OP-TEE RPMB driver.

Why:
1. ufs_rpmb_bus_type was never registered with bus_register(), causing
   device_register() in ufs_rpmb_probe() to unconditionally fail with
   -EINVAL.
2. struct ufs_rpmb_dev embeds struct device but was allocated via
   devm_kzalloc() tied to hba->dev. On host unbind, devres frees the
   structure prematurely while external references remain active,
   causing a Use-After-Free (UAF) Oops.

What:
- Patch 1: Register ufs_rpmb_bus_type during ufshcd_core_init() and
  unregister it in ufshcd_core_exit(), with stubs for !CONFIG_RPMB.
- Patch 2: Allocate ufs_rpmb with kzalloc_obj() and free it via kfree()
  in ufs_rpmb_device_release(). Pin the underlying SCSI WLUN via
  scsi_device_get/put() and unregister in ufs_rpmb_remove().

Differences from v2:
- Drop generic RPMB core changes (sent as a separate patch).
- Reorder patches so bus registration comes first for bisectability.
- Call rpmb_dev_unregister() in ufs_rpmb_remove() to break cyclic refcount.
- Pin underlying SCSI WLUN via scsi_device_get/put().

Tested:
- Verified clean probe, RPMB I/O, and unbind on QEMU ARM64 without UAF.

Stanley Jhu (2):
  scsi: ufs: rpmb: Register and unregister ufs_rpmb_bus_type
  scsi: ufs: rpmb: Decouple device lifecycle from devres to avoid UAF

 drivers/ufs/core/ufs-rpmb.c    | 107 ++++++++++++++++++++-------------
 drivers/ufs/core/ufshcd-priv.h |  13 +++-
 drivers/ufs/core/ufshcd.c      |  16 ++++-
 3 files changed, 91 insertions(+), 45 deletions(-)

-- 
2.55.0.1007.g17ff1f9808-goog

[PATCH v3 1/2] scsi: ufs: rpmb: Register and unregister ufs_rpmb_bus_type

[Stanley Jhu]

The UFS RPMB driver defines ufs_rpmb_bus_type and assigns it to the bus
member of struct device for each RPMB device. However, ufs_rpmb_bus_type
is never registered with the driver core via bus_register().

When driver core rejects devices assigned to unregistered buses with
-EINVAL in bus_add_device(), device_register(&ufs_rpmb->dev) in
ufs_rpmb_probe() fails with:
  "bus_add_device: cannot add device 'ufs_rpmb0' to unregistered bus
   'ufs_rpmb'"
  "ufshcd: Failed to register UFS RPMB device 0"

Fix this by registering ufs_rpmb_bus_type during UFS core initialization
in ufshcd_core_init() and unregistering it in ufshcd_core_exit(). Add
helper functions ufs_rpmb_bus_register() and ufs_rpmb_bus_unregister(),
guarding their declarations with IS_REACHABLE(CONFIG_RPMB) and inline
fallback stubs for configurations where CONFIG_RPMB is disabled. Mark
ufs_rpmb_bus_register() as __init so its memory can be reclaimed after
module initialization.

Fixes: b06b8c421485 ("scsi: ufs: core: Add OP-TEE based RPMB driver for UFS devices")
Signed-off-by: Stanley Jhu <stanleyjhu@google.com>
---
 drivers/ufs/core/ufs-rpmb.c    | 10 ++++++++++
 drivers/ufs/core/ufshcd-priv.h | 13 ++++++++++++-
 drivers/ufs/core/ufshcd.c      | 16 ++++++++++++++--
 3 files changed, 36 insertions(+), 3 deletions(-)

diff --git a/drivers/ufs/core/ufs-rpmb.c b/drivers/ufs/core/ufs-rpmb.c
index aa925cbb07e8..c7aade96c823 100644
--- a/drivers/ufs/core/ufs-rpmb.c
+++ b/drivers/ufs/core/ufs-rpmb.c
@@ -28,6 +28,16 @@ static const struct bus_type ufs_rpmb_bus_type = {
 	.name = "ufs_rpmb",
 };
 
+int __init ufs_rpmb_bus_register(void)
+{
+	return bus_register(&ufs_rpmb_bus_type);
+}
+
+void ufs_rpmb_bus_unregister(void)
+{
+	bus_unregister(&ufs_rpmb_bus_type);
+}
+
 /* UFS RPMB device structure */
 struct ufs_rpmb_dev {
 	u8 region_id;
diff --git a/drivers/ufs/core/ufshcd-priv.h b/drivers/ufs/core/ufshcd-priv.h
index e55c2a02c1f5..d5e0cc3edb5b 100644
--- a/drivers/ufs/core/ufshcd-priv.h
+++ b/drivers/ufs/core/ufshcd-priv.h
@@ -493,10 +493,21 @@ static inline u32 ufshcd_mcq_get_sq_head_slot(struct ufs_hw_queue *q)
 	return val / sizeof(struct utp_transfer_req_desc);
 }
 
-#if IS_ENABLED(CONFIG_RPMB)
+#if IS_REACHABLE(CONFIG_RPMB)
+int __init ufs_rpmb_bus_register(void);
+void ufs_rpmb_bus_unregister(void);
 int ufs_rpmb_probe(struct ufs_hba *hba);
 void ufs_rpmb_remove(struct ufs_hba *hba);
 #else
+static inline int ufs_rpmb_bus_register(void)
+{
+	return 0;
+}
+
+static inline void ufs_rpmb_bus_unregister(void)
+{
+}
+
 static inline int ufs_rpmb_probe(struct ufs_hba *hba)
 {
 	return 0;
diff --git a/drivers/ufs/core/ufshcd.c b/drivers/ufs/core/ufshcd.c
index a25b6a0cb5c6..4470e3d65c5c 100644
--- a/drivers/ufs/core/ufshcd.c
+++ b/drivers/ufs/core/ufshcd.c
@@ -11584,16 +11584,28 @@ static int __init ufshcd_core_init(void)
 
 	ufs_debugfs_init();
 
+	ret = ufs_rpmb_bus_register();
+	if (ret)
+		goto err_debugfs;
+
 	ret = scsi_register_driver(&ufs_dev_wlun_template);
 	if (ret)
-		ufs_debugfs_exit();
+		goto err_rpmb_bus;
+
+	return 0;
+
+err_rpmb_bus:
+	ufs_rpmb_bus_unregister();
+err_debugfs:
+	ufs_debugfs_exit();
 	return ret;
 }
 
 static void __exit ufshcd_core_exit(void)
 {
-	ufs_debugfs_exit();
 	scsi_unregister_driver(&ufs_dev_wlun_template);
+	ufs_rpmb_bus_unregister();
+	ufs_debugfs_exit();
 }
 
 module_init(ufshcd_core_init);
-- 
2.55.0.1007.g17ff1f9808-goog

[PATCH v3 2/2] scsi: ufs: rpmb: Decouple device lifecycle from devres to avoid UAF

[Stanley Jhu]

struct ufs_rpmb_dev embeds struct device, but is allocated using
devm_kzalloc() tied to the host controller (hba->dev).

When the host controller unbinds, devres automatically frees ufs_rpmb
regardless of active references to ufs_rpmb->dev (such as sysfs users or
child devices). Subsequent access to ufs_rpmb->dev triggers a
Use-After-Free (UAF) kernel Oops.

Fix this lifetime defect:
- Allocate ufs_rpmb with kzalloc_obj() and free it in
  ufs_rpmb_device_release() via kfree(), strictly tying memory lifetime
  to the device reference count.
- Pin the underlying SCSI WLUN via scsi_device_get() in probe and
  release it with scsi_device_put() in device_release.
- Call rpmb_dev_unregister() in ufs_rpmb_remove() and probe error unwind
  before device_unregister().
- Check scsi_device_online() before submitting security commands.

Fixes: b06b8c421485 ("scsi: ufs: core: Add OP-TEE based RPMB driver for UFS devices")
Signed-off-by: Stanley Jhu <stanleyjhu@google.com>
Cc: stable@vger.kernel.org
---
 drivers/ufs/core/ufs-rpmb.c | 97 +++++++++++++++++++++----------------
 1 file changed, 55 insertions(+), 42 deletions(-)

diff --git a/drivers/ufs/core/ufs-rpmb.c b/drivers/ufs/core/ufs-rpmb.c
index c7aade96c823..33b9a4a1b120 100644
--- a/drivers/ufs/core/ufs-rpmb.c
+++ b/drivers/ufs/core/ufs-rpmb.c
@@ -13,6 +13,7 @@
 #include <linux/module.h>
 #include <linux/device.h>
 #include <linux/kernel.h>
+#include <linux/slab.h>
 #include <linux/types.h>
 #include <linux/rpmb.h>
 #include <linux/string.h>
@@ -43,15 +44,19 @@ struct ufs_rpmb_dev {
 	u8 region_id;
 	struct device dev;
 	struct rpmb_dev *rdev;
-	struct ufs_hba *hba;
+	struct scsi_device *sdev;
 	struct list_head node;
 };
 
-static int ufs_sec_submit(struct ufs_hba *hba, u16 spsp, void *buffer, size_t len, bool send)
+static int ufs_sec_submit(struct ufs_rpmb_dev *ufs_rpmb, u16 spsp,
+			  void *buffer, size_t len, bool send)
 {
-	struct scsi_device *sdev = hba->ufs_rpmb_wlun;
+	struct scsi_device *sdev = ufs_rpmb->sdev;
 	u8 cdb[12] = { };
 
+	if (!sdev || !scsi_device_online(sdev))
+		return -ENODEV;
+
 	cdb[0] = send ? SECURITY_PROTOCOL_OUT : SECURITY_PROTOCOL_IN;
 	cdb[1] = UFS_RPMB_SEC_PROTOCOL;
 	put_unaligned_be16(spsp, &cdb[2]);
@@ -63,13 +68,12 @@ static int ufs_sec_submit(struct ufs_hba *hba, u16 spsp, void *buffer, size_t le
 
 /* UFS RPMB route frames implementation */
 static int ufs_rpmb_route_frames(struct device *dev, u8 *req, unsigned int req_len, u8 *resp,
-					unsigned int resp_len)
+				 unsigned int resp_len)
 {
 	struct ufs_rpmb_dev *ufs_rpmb = dev_get_drvdata(dev);
 	struct rpmb_frame *frm_out = (struct rpmb_frame *)req;
 	bool need_result_read = true;
 	u16 req_type, protocol_id;
-	struct ufs_hba *hba;
 	int ret;
 
 	if (!ufs_rpmb) {
@@ -77,8 +81,6 @@ static int ufs_rpmb_route_frames(struct device *dev, u8 *req, unsigned int req_l
 		return -ENODEV;
 	}
 
-	hba = ufs_rpmb->hba;
-
 	/* req_resp is at the end of an RPMB frame. */
 	if (req_len < sizeof(*frm_out))
 		return -EINVAL;
@@ -111,7 +113,7 @@ static int ufs_rpmb_route_frames(struct device *dev, u8 *req, unsigned int req_l
 
 	protocol_id = ufs_rpmb->region_id << 8 | UFS_RPMB_SEC_PROTOCOL_ID;
 
-	ret = ufs_sec_submit(hba, protocol_id, req, req_len, true);
+	ret = ufs_sec_submit(ufs_rpmb, protocol_id, req, req_len, true);
 	if (ret) {
 		dev_err(dev, "Command failed with ret=%d\n", ret);
 		return ret;
@@ -122,7 +124,7 @@ static int ufs_rpmb_route_frames(struct device *dev, u8 *req, unsigned int req_l
 
 		memset(frm_resp, 0, sizeof(*frm_resp));
 		put_unaligned_be16(RPMB_RESULT_READ, &frm_resp->req_resp);
-		ret = ufs_sec_submit(hba, protocol_id, resp, resp_len, true);
+		ret = ufs_sec_submit(ufs_rpmb, protocol_id, resp, resp_len, true);
 		if (ret) {
 			dev_err(dev, "Result read request failed with ret=%d\n", ret);
 			return ret;
@@ -130,7 +132,7 @@ static int ufs_rpmb_route_frames(struct device *dev, u8 *req, unsigned int req_l
 	}
 
 	if (!ret) {
-		ret = ufs_sec_submit(hba, protocol_id, resp, resp_len, false);
+		ret = ufs_sec_submit(ufs_rpmb, protocol_id, resp, resp_len, false);
 		if (ret)
 			dev_err(dev, "Response read failed with ret=%d\n", ret);
 	}
@@ -140,22 +142,29 @@ static int ufs_rpmb_route_frames(struct device *dev, u8 *req, unsigned int req_l
 
 static void ufs_rpmb_device_release(struct device *dev)
 {
-	struct ufs_rpmb_dev *ufs_rpmb = dev_get_drvdata(dev);
+	struct ufs_rpmb_dev *ufs_rpmb = container_of(dev, struct ufs_rpmb_dev, dev);
 
-	rpmb_dev_unregister(ufs_rpmb->rdev);
+	scsi_device_put(ufs_rpmb->sdev);
+	kfree(ufs_rpmb);
 }
 
 /* UFS RPMB device registration */
 int ufs_rpmb_probe(struct ufs_hba *hba)
 {
+	struct rpmb_descr descr = {
+		.type = RPMB_TYPE_UFS,
+		.route_frames = ufs_rpmb_route_frames,
+		.reliable_wr_count = hba->dev_info.rpmb_io_size,
+	};
+	struct scsi_device *sdev = hba->ufs_rpmb_wlun;
 	struct ufs_rpmb_dev *ufs_rpmb, *it, *tmp;
 	struct rpmb_dev *rdev;
-	char *cid = NULL;
+	char *cid;
 	int region;
 	u32 cap;
 	int ret;
 
-	if (!hba->ufs_rpmb_wlun || hba->dev_info.b_advanced_rpmb_en) {
+	if (!sdev || hba->dev_info.b_advanced_rpmb_en) {
 		dev_info(hba->dev, "Skip OP-TEE RPMB registration\n");
 		return -ENODEV;
 	}
@@ -166,25 +175,28 @@ int ufs_rpmb_probe(struct ufs_hba *hba)
 		return -EINVAL;
 	}
 
-	struct rpmb_descr descr = {
-		.type = RPMB_TYPE_UFS,
-		.route_frames = ufs_rpmb_route_frames,
-		.reliable_wr_count = hba->dev_info.rpmb_io_size,
-	};
-
 	for (region = 0; region < ARRAY_SIZE(hba->dev_info.rpmb_region_size); region++) {
 		cap = hba->dev_info.rpmb_region_size[region];
 		if (!cap)
 			continue;
 
-		ufs_rpmb = devm_kzalloc(hba->dev, sizeof(*ufs_rpmb), GFP_KERNEL);
+		ufs_rpmb = kzalloc_obj(*ufs_rpmb);
 		if (!ufs_rpmb) {
 			ret = -ENOMEM;
 			goto err_out;
 		}
 
-		ufs_rpmb->hba = hba;
-		ufs_rpmb->dev.parent = &hba->ufs_rpmb_wlun->sdev_gendev;
+		INIT_LIST_HEAD(&ufs_rpmb->node);
+
+		ret = scsi_device_get(sdev);
+		if (ret) {
+			kfree(ufs_rpmb);
+			goto err_out;
+		}
+
+		ufs_rpmb->sdev = sdev;
+		ufs_rpmb->region_id = region;
+		ufs_rpmb->dev.parent = &sdev->sdev_gendev;
 		ufs_rpmb->dev.bus = &ufs_rpmb_bus_type;
 		ufs_rpmb->dev.release = ufs_rpmb_device_release;
 		dev_set_name(&ufs_rpmb->dev, "ufs_rpmb%d", region);
@@ -195,16 +207,14 @@ int ufs_rpmb_probe(struct ufs_hba *hba)
 		ret = device_register(&ufs_rpmb->dev);
 		if (ret) {
 			dev_err(hba->dev, "Failed to register UFS RPMB device %d\n", region);
-			put_device(&ufs_rpmb->dev);
-			goto err_out;
+			goto err_put;
 		}
 
 		/* Create unique ID by appending region number to device_id */
 		cid = kasprintf(GFP_KERNEL, "%s-R%d", hba->dev_info.device_id, region);
 		if (!cid) {
-			device_unregister(&ufs_rpmb->dev);
 			ret = -ENOMEM;
-			goto err_out;
+			goto err_unreg;
 		}
 
 		descr.dev_id = cid;
@@ -213,29 +223,33 @@ int ufs_rpmb_probe(struct ufs_hba *hba)
 
 		/* Register RPMB device */
 		rdev = rpmb_dev_register(&ufs_rpmb->dev, &descr);
+		kfree(cid);
 		if (IS_ERR(rdev)) {
 			dev_err(hba->dev, "Failed to register UFS RPMB device.\n");
-			device_unregister(&ufs_rpmb->dev);
 			ret = PTR_ERR(rdev);
-			goto err_out;
+			goto err_unreg;
 		}
 
-		kfree(cid);
-		cid = NULL;
-
 		ufs_rpmb->rdev = rdev;
-		ufs_rpmb->region_id = region;
-
 		list_add_tail(&ufs_rpmb->node, &hba->rpmbs);
 
 		dev_info(hba->dev, "UFS RPMB region %d registered (capacity=%u)\n", region, cap);
 	}
 
 	return 0;
+
+err_unreg:
+	device_unregister(&ufs_rpmb->dev);
+	goto err_out;
+err_put:
+	put_device(&ufs_rpmb->dev);
 err_out:
-	kfree(cid);
 	list_for_each_entry_safe(it, tmp, &hba->rpmbs, node) {
-		list_del(&it->node);
+		list_del_init(&it->node);
+		if (it->rdev) {
+			rpmb_dev_unregister(it->rdev);
+			it->rdev = NULL;
+		}
 		device_unregister(&it->dev);
 	}
 
@@ -252,14 +266,13 @@ void ufs_rpmb_remove(struct ufs_hba *hba)
 
 	/* Remove all registered RPMB devices */
 	list_for_each_entry_safe(ufs_rpmb, tmp, &hba->rpmbs, node) {
-		dev_info(hba->dev, "Removing UFS RPMB region %d\n", ufs_rpmb->region_id);
-		/* Remove from list first */
-		list_del(&ufs_rpmb->node);
-		/* Unregister device */
+		list_del_init(&ufs_rpmb->node);
+		if (ufs_rpmb->rdev) {
+			rpmb_dev_unregister(ufs_rpmb->rdev);
+			ufs_rpmb->rdev = NULL;
+		}
 		device_unregister(&ufs_rpmb->dev);
 	}
-
-	dev_info(hba->dev, "All UFS RPMB devices unregistered\n");
 }
 
 MODULE_LICENSE("GPL v2");
-- 
2.55.0.1007.g17ff1f9808-goog

Re: [PATCH v3 2/2] scsi: ufs: rpmb: Decouple device lifecycle from devres to avoid UAF

[sashiko-bot]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:

Pre-existing issues:
- [Critical] This problem wasn't introduced by this patch, but the patch fails to resolve the pre-existing Use-After-Free during device removal. The device model's `device_del()` drops the parent reference, meaning `rdev->dev.parent` becomes a dangling pointer if a consumer holds a reference to `rdev`.
--

commit 19c2abff2bd57dbeee481738657ea4d9e1123a19
Author: Stanley Jhu <stanleyjhu@google.com>

scsi: ufs: rpmb: Decouple device lifecycle from devres to avoid UAF

This commit changes the allocation of the UFS RPMB device from devres to
a reference-counted lifecycle. It also explicitly unregisters the RPMB
child device during host removal before unregistering the parent device
to prevent memory safety issues.

Cc: stable@vger.kernel.org

> diff --git a/drivers/ufs/core/ufs-rpmb.c b/drivers/ufs/core/ufs-rpmb.c
> index c7aade96c823e..33b9a4a1b120e 100644
> --- a/drivers/ufs/core/ufs-rpmb.c
> +++ b/drivers/ufs/core/ufs-rpmb.c

[ ... ]

> @@ -252,14 +266,13 @@ void ufs_rpmb_remove(struct ufs_hba *hba)
>  
>  	/* Remove all registered RPMB devices */
>  	list_for_each_entry_safe(ufs_rpmb, tmp, &hba->rpmbs, node) {
> -		dev_info(hba->dev, "Removing UFS RPMB region %d\n", ufs_rpmb->region_id);
> -		/* Remove from list first */
> -		list_del(&ufs_rpmb->node);
> -		/* Unregister device */
> +		list_del_init(&ufs_rpmb->node);
> +		if (ufs_rpmb->rdev) {
> +			rpmb_dev_unregister(ufs_rpmb->rdev);
> +			ufs_rpmb->rdev = NULL;
> +		}
>  		device_unregister(&ufs_rpmb->dev);

[Severity: Critical]
This isn't a bug introduced by this patch, but does this sequence still
leave a use-after-free window during device removal?

When rpmb_dev_unregister() is called, it internally calls device_del() on
the child device, which immediately drops the reference to its parent device
(ufs_rpmb->dev).

If a consumer is actively holding a reference to the child device via
rpmb_dev_get(), the child device itself remains allocated. However, the
subsequent call to device_unregister() here drops the final reference to
the parent ufs_rpmb structure, causing it to be freed.

If the consumer then concurrently executes a request, the framework will
pass the now-dangling parent pointer to the route_frames callback:

drivers/ufs/core/ufs-rpmb.c:ufs_rpmb_route_frames() {
    struct ufs_rpmb_dev *ufs_rpmb = dev_get_drvdata(dev);
    ...
}

Could this dev_get_drvdata(dev) dereference the freed parent memory,
resulting in a use-after-free despite the new lifecycle management?

>  	}
> -
> -	dev_info(hba->dev, "All UFS RPMB devices unregistered\n");
>  }
>  
>  MODULE_LICENSE("GPL v2");

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260910015503.1991119-1-stanleyjhu@google.com?part=2

Re: [PATCH v3 2/2] scsi: ufs: rpmb: Decouple device lifecycle from devres to avoid UAF

[Stanley Jhu]

On Thu, 10 Sep 2026, sashiko-bot@kernel.org wrote:
> [Severity: Critical]
> This isn't a bug introduced by this patch, but does this sequence still
> leave a use-after-free window during device removal?
> 
> When rpmb_dev_unregister() is called, it internally calls device_del() on
> the child device, which immediately drops the reference to its parent device
> (ufs_rpmb->dev).
> 
> If a consumer is actively holding a reference to the child device via
> rpmb_dev_get(), the child device itself remains allocated. However, the
> subsequent call to device_unregister() here drops the final reference to
> the parent ufs_rpmb structure, causing it to be freed.
> 
> If the consumer then concurrently executes a request, the framework will
> pass the now-dangling parent pointer to the route_frames callback:
> 
> drivers/ufs/core/ufs-rpmb.c:ufs_rpmb_route_frames() {
>     struct ufs_rpmb_dev *ufs_rpmb = dev_get_drvdata(dev);
>     ...
> }
> 
> Could this dev_get_drvdata(dev) dereference the freed parent memory,
> resulting in a use-after-free despite the new lifecycle management?

This specific teardown race is guarded by the companion patch in the
generic RPMB core:
"[PATCH v3] rpmb: core: Guard frame requests and teardown with mutex"
https://lore.kernel.org/r/20260910015515.1991789-1-stanleyjhu@google.com

In rpmb_dev_unregister(), rdev->lock is acquired to drain in-flight
requests and mark rdev->dead = true before device_del() is invoked.
Any concurrent or subsequent call to rpmb_route_frames() is rejected
with -ENODEV under rdev->lock before dereferencing rdev->dev.parent.

Therefore, the dangling parent pointer is never dereferenced once
rpmb_dev_unregister() returns.

Thanks,
Stanley

Re: [PATCH v3 0/2] scsi: ufs: rpmb: Fix bus registration and device lifecycle

[Stanley Jhu]

For reference, the companion patch guarding the generic RPMB core with
mutex has been submitted to Jens Wiklander and LKML here:
https://lore.kernel.org/r/20260910015515.1991789-1-stanleyjhu@google.com

Thanks,
Stanley