habanalabs: protect access to dynamic mem 'user_mappings'

When HL_INFO_USER_MAPPINGS IOCTL is called, we copy_to_user from
a dynamically allocated memory - 'user_mappings'.
Since freeing/allocating it happens in runtime (upon a page fault),
it not unlikely to access it even before being initially allocated
(i.e., accessing a NULL pointer).

The solution is to simply mark the spot when the err info has been
collected, and that way to know whether err info (either page fault
or RAZWI) is available to be read.
Signed-off-by: Koby Elbaz <kelbaz@habana.ai>
Reviewed-by: Oded Gabbay <ogabbay@kernel.org>
Signed-off-by: Oded Gabbay <ogabbay@kernel.org>

drivers/accel/habanalabs/common/device.c

@@ -2441,6 +2441,8 @@ void hl_capture_razwi(struct hl_device *hdev, u64 addr, u16 *engine_id, u16 num_
 	memcpy(&razwi_info->razwi.engine_id[0], &engine_id[0],
 			num_of_engines * sizeof(u16));
 	razwi_info->razwi.flags = flags;
+
+	razwi_info->razwi_info_available = true;
 }
 
 void hl_handle_razwi(struct hl_device *hdev, u64 addr, u16 *engine_id, u16 num_of_engines,
@@ -2526,6 +2528,8 @@ void hl_capture_page_fault(struct hl_device *hdev, u64 addr, u16 eng_id, bool is
 	pgf_info->page_fault.addr = addr;
 	pgf_info->page_fault.engine_id = eng_id;
 	hl_capture_user_mappings(hdev, is_pmmu);
+
+	pgf_info->page_fault_info_available = true;
 }
 
 void hl_handle_page_fault(struct hl_device *hdev, u64 addr, u16 eng_id, bool is_pmmu,

drivers/accel/habanalabs/common/habanalabs.h

@@ -2984,12 +2984,14 @@ struct undefined_opcode_info {
  *                       Since we're looking for the page-fault's root cause,
  *                       we don't care of the others that might follow it-
  *                       so once changed to 1, it will remain that way.
+ * @page_fault_info_available: indicates that a page fault info is now available.
  */
 struct page_fault_info {
 	struct hl_page_fault_info	page_fault;
 	struct hl_user_mapping		*user_mappings;
 	u64				num_of_user_mappings;
 	atomic_t			page_fault_detected;
+	bool				page_fault_info_available;
 };
 
 /**
@@ -3000,10 +3002,12 @@ struct page_fault_info {
  *                  Since we're looking for the RAZWI's root cause,
  *                  we don't care of the others that might follow it-
  *                  so once changed to 1, it will remain that way.
+ * @razwi_info_available: indicates that a RAZWI info is now available.
  */
 struct razwi_info {
 	struct hl_info_razwi_event	razwi;
 	atomic_t			razwi_detected;
+	bool				razwi_info_available;
 };
 
 /**

drivers/accel/habanalabs/common/habanalabs_drv.c

@@ -225,6 +225,8 @@ int hl_device_open(struct inode *inode, struct file *filp)
 	atomic_set(&hdev->captured_err_info.razwi_info.razwi_detected, 0);
 	atomic_set(&hdev->captured_err_info.page_fault_info.page_fault_detected, 0);
 	hdev->captured_err_info.undef_opcode.write_enable = true;
+	hdev->captured_err_info.razwi_info.razwi_info_available = false;
+	hdev->captured_err_info.page_fault_info.page_fault_info_available = false;
 
 	hdev->open_counter++;
 	hdev->last_successful_open_jif = jiffies;

drivers/accel/habanalabs/common/habanalabs_ioctl.c

@@ -607,16 +607,20 @@ static int cs_timeout_info(struct hl_fpriv *hpriv, struct hl_info_args *args)
 
 static int razwi_info(struct hl_fpriv *hpriv, struct hl_info_args *args)
 {
+	void __user *out = (void __user *) (uintptr_t) args->return_pointer;
 	struct hl_device *hdev = hpriv->hdev;
 	u32 max_size = args->return_size;
-	struct hl_info_razwi_event *info = &hdev->captured_err_info.razwi_info.razwi;
-	void __user *out = (void __user *) (uintptr_t) args->return_pointer;
+	struct razwi_info *razwi_info;
 
 	if ((!max_size) || (!out))
 		return -EINVAL;
 
-	return copy_to_user(out, info, min_t(size_t, max_size, sizeof(struct hl_info_razwi_event)))
-				? -EFAULT : 0;
+	razwi_info = &hdev->captured_err_info.razwi_info;
+	if (!razwi_info->razwi_info_available)
+		return 0;
+
+	return copy_to_user(out, &razwi_info->razwi,
+			min_t(size_t, max_size, sizeof(struct hl_info_razwi_event))) ? -EFAULT : 0;
 }
 
 static int undefined_opcode_info(struct hl_fpriv *hpriv, struct hl_info_args *args)
@@ -786,16 +790,20 @@ static int engine_status_info(struct hl_fpriv *hpriv, struct hl_info_args *args)
 
 static int page_fault_info(struct hl_fpriv *hpriv, struct hl_info_args *args)
 {
+	void __user *out = (void __user *) (uintptr_t) args->return_pointer;
 	struct hl_device *hdev = hpriv->hdev;
 	u32 max_size = args->return_size;
-	struct hl_page_fault_info *info = &hdev->captured_err_info.page_fault_info.page_fault;
-	void __user *out = (void __user *) (uintptr_t) args->return_pointer;
+	struct page_fault_info *pgf_info;
 
 	if ((!max_size) || (!out))
 		return -EINVAL;
 
-	return copy_to_user(out, info, min_t(size_t, max_size, sizeof(struct hl_page_fault_info)))
-				? -EFAULT : 0;
+	pgf_info = &hdev->captured_err_info.page_fault_info;
+	if (!pgf_info->page_fault_info_available)
+		return 0;
+
+	return copy_to_user(out, &pgf_info->page_fault,
+			min_t(size_t, max_size, sizeof(struct hl_page_fault_info))) ? -EFAULT : 0;
 }
 
 static int user_mappings_info(struct hl_fpriv *hpriv, struct hl_info_args *args)
@@ -806,18 +814,20 @@ static int user_mappings_info(struct hl_fpriv *hpriv, struct hl_info_args *args)
 	struct page_fault_info *pgf_info;
 	u64 actual_size;
 
-	pgf_info = &hdev->captured_err_info.page_fault_info;
-	args->array_size = pgf_info->num_of_user_mappings;
-
 	if (!out)
 		return -EINVAL;
 
+	pgf_info = &hdev->captured_err_info.page_fault_info;
+	if (!pgf_info->page_fault_info_available)
+		return 0;
+
+	args->array_size = pgf_info->num_of_user_mappings;
+
 	actual_size = pgf_info->num_of_user_mappings * sizeof(struct hl_user_mapping);
 	if (user_buf_size < actual_size)
 		return -ENOMEM;
 
-	return copy_to_user(out, pgf_info->user_mappings, min_t(size_t, user_buf_size, actual_size))
-				? -EFAULT : 0;
+	return copy_to_user(out, pgf_info->user_mappings, actual_size) ? -EFAULT : 0;
 }
 
 static int send_fw_generic_request(struct hl_device *hdev, struct hl_info_args *info_args)