[PATCH] crypto: qat - fix Use-After-Free in adf_ctl_ioctl_dev_start()

[w15303746062@163.com]

From: Mingyu Wang <25181214217@stu.xidian.edu.cn>

A severe Use-After-Free (UAF) vulnerability, which KASAN detects as a
slab-out-of-bounds access, was identified in the QAT driver's ioctl path.

When handling commands like IOCTL_START_ACCEL_DEV, various functions
retrieve the acceleration device using adf_devmgr_get_dev_by_id().
Currently, this lookup function iterates over the accel_table under
the table_lock. However, once the target device is found, the lock is
dropped and a bare pointer is returned without bumping the device's
reference count.

This creates a critical race condition. If a concurrent thread removes
the device (e.g., via device stop operations or PCIe hotplug) by calling
adf_devmgr_rm_dev(), the device is removed from the list and its memory
is subsequently freed. When the original ioctl thread resumes and attempts
to acquire accel_dev->state_lock inside adf_dev_up(), it triggers a
KASAN panic.

Fix this by acquiring the reference count inside adf_devmgr_get_dev_by_id()
via adf_dev_get() while the table_lock is still held. If adf_dev_get()
fails (e.g., the module is unloading), we safely break the loop and treat
the device as not found. All callers of adf_devmgr_get_dev_by_id() are then
updated to properly release the reference using adf_dev_put() when done.

Signed-off-by: Mingyu Wang <25181214217@stu.xidian.edu.cn>
---
 .../crypto/intel/qat/qat_common/adf_ctl_drv.c  | 16 ++++++++++++++++
 .../crypto/intel/qat/qat_common/adf_dev_mgr.c  | 18 +++++++++++++++---
 2 files changed, 31 insertions(+), 3 deletions(-)

diff --git a/drivers/crypto/intel/qat/qat_common/adf_ctl_drv.c b/drivers/crypto/intel/qat/qat_common/adf_ctl_drv.c
index c2e6f0cb7480..0519cc02e634 100644
--- a/drivers/crypto/intel/qat/qat_common/adf_ctl_drv.c
+++ b/drivers/crypto/intel/qat/qat_common/adf_ctl_drv.c
@@ -201,6 +201,10 @@ static int adf_ctl_ioctl_dev_config(struct file *fp, unsigned int cmd,
 	}
 	set_bit(ADF_STATUS_CONFIGURED, &accel_dev->status);
 out:
+	/* Release the reference acquired by adf_devmgr_get_dev_by_id() */
+	if (accel_dev)
+		adf_dev_put(accel_dev);
+
 	kfree(ctl_data);
 	return ret;
 }
@@ -278,6 +282,10 @@ static int adf_ctl_ioctl_dev_stop(struct file *fp, unsigned int cmd,
 	adf_ctl_stop_devices(ctl_data->device_id);
 
 out:
+	/* Release the reference acquired by adf_devmgr_get_dev_by_id() */
+	if (accel_dev)
+		adf_dev_put(accel_dev);
+
 	kfree(ctl_data);
 	return ret;
 }
@@ -310,6 +318,10 @@ static int adf_ctl_ioctl_dev_start(struct file *fp, unsigned int cmd,
 		adf_dev_down(accel_dev);
 	}
 out:
+	/* Release the reference acquired by adf_devmgr_get_dev_by_id() */
+	if (accel_dev)
+		adf_dev_put(accel_dev);
+
 	kfree(ctl_data);
 	return ret;
 }
@@ -360,8 +372,12 @@ static int adf_ctl_ioctl_get_status(struct file *fp, unsigned int cmd,
 	if (copy_to_user((void __user *)arg, &dev_info,
 			 sizeof(struct adf_dev_status_info))) {
 		dev_err(&GET_DEV(accel_dev), "failed to copy status.\n");
+		adf_dev_put(accel_dev);
 		return -EFAULT;
 	}
+	/* Release the reference acquired by adf_devmgr_get_dev_by_id() */
+	adf_dev_put(accel_dev);
+
 	return 0;
 }
 
diff --git a/drivers/crypto/intel/qat/qat_common/adf_dev_mgr.c b/drivers/crypto/intel/qat/qat_common/adf_dev_mgr.c
index e050de16ab5d..5e9313d8bacf 100644
--- a/drivers/crypto/intel/qat/qat_common/adf_dev_mgr.c
+++ b/drivers/crypto/intel/qat/qat_common/adf_dev_mgr.c
@@ -320,8 +320,14 @@ struct adf_accel_dev *adf_devmgr_get_dev_by_id(u32 id)
 		struct adf_accel_dev *ptr =
 				list_entry(itr, struct adf_accel_dev, list);
 		if (ptr->accel_id == id) {
-			mutex_unlock(&table_lock);
-			return ptr;
+			/* Increment refcount to prevent UAF during removal.
+			 * If adf_dev_get() fails, the module is unloading.
+			 */
+			if (adf_dev_get(ptr) == 0) {
+				mutex_unlock(&table_lock);
+				return ptr;
+			}
+			break;
 		}
 	}
 unlock:
@@ -331,11 +337,17 @@ struct adf_accel_dev *adf_devmgr_get_dev_by_id(u32 id)
 
 int adf_devmgr_verify_id(u32 id)
 {
+	struct adf_accel_dev *accel_dev;
+
 	if (id == ADF_CFG_ALL_DEVICES)
 		return 0;
 
-	if (adf_devmgr_get_dev_by_id(id))
+	accel_dev = adf_devmgr_get_dev_by_id(id);
+	if (accel_dev) {
+		/* Release the reference immediately as we only verify existence */
+		adf_dev_put(accel_dev);
 		return 0;
+	}
 
 	return -ENODEV;
 }
-- 
2.34.1