[PATCH v2 1/3] lib, include/linux: add usercopy failure capability

[albert.linde@gmail.com]

From: Albert van der Linde <alinde@google.com>

Add a failure injection capability to improve testing of fault-tolerance
in usages of user memory access functions.

Add CONFIG_FAULT_INJECTION_USERCOPY to enable faults in usercopy
functions. The should_fail_usercopy function is to be called by these
functions (copy_from_user, get_user, ...) in order to fail or not.

Signed-off-by: Albert van der Linde <alinde@google.com>
---
v2:
 - adressed comments from Dmitry Vyukov
 - removed failsize
 - changed should_fail function to return bool
---
 .../admin-guide/kernel-parameters.txt         |  1 +
 .../fault-injection/fault-injection.rst       |  7 +++-
 include/linux/fault-inject-usercopy.h         | 22 +++++++++++
 lib/Kconfig.debug                             |  7 ++++
 lib/Makefile                                  |  1 +
 lib/fault-inject-usercopy.c                   | 39 +++++++++++++++++++
 6 files changed, 76 insertions(+), 1 deletion(-)
 create mode 100644 include/linux/fault-inject-usercopy.h
 create mode 100644 lib/fault-inject-usercopy.c

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index a1068742a6df..790e54988d4f 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -1332,6 +1332,7 @@
 			current integrity status.
 
 	failslab=
+	fail_usercopy=
 	fail_page_alloc=
 	fail_make_request=[KNL]
 			General fault injection mechanism.
diff --git a/Documentation/fault-injection/fault-injection.rst b/Documentation/fault-injection/fault-injection.rst
index f850ad018b70..31ecfe44e5b4 100644
--- a/Documentation/fault-injection/fault-injection.rst
+++ b/Documentation/fault-injection/fault-injection.rst
@@ -16,6 +16,10 @@ Available fault injection capabilities
 
   injects page allocation failures. (alloc_pages(), get_free_pages(), ...)
 
+- fail_usercopy
+
+  injects failures in user memory access functions. (copy_from_user(), get_user(), ...)
+
 - fail_futex
 
   injects futex deadlock and uaddr fault errors.
@@ -177,6 +181,7 @@ use the boot option::
 
 	failslab=
 	fail_page_alloc=
+	fail_usercopy=
 	fail_make_request=
 	fail_futex=
 	mmc_core.fail_request=<interval>,<probability>,<space>,<times>
@@ -222,7 +227,7 @@ How to add new fault injection capability
 
 - debugfs entries
 
-  failslab, fail_page_alloc, and fail_make_request use this way.
+  failslab, fail_page_alloc, fail_usercopy, and fail_make_request use this way.
   Helper functions:
 
 	fault_create_debugfs_attr(name, parent, attr);
diff --git a/include/linux/fault-inject-usercopy.h b/include/linux/fault-inject-usercopy.h
new file mode 100644
index 000000000000..56c3a693fdd9
--- /dev/null
+++ b/include/linux/fault-inject-usercopy.h
@@ -0,0 +1,22 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __LINUX_FAULT_INJECT_USERCOPY_H__
+#define __LINUX_FAULT_INJECT_USERCOPY_H__
+
+/*
+ * This header provides a wrapper for injecting failures to user space memory
+ * access functions.
+ */
+
+#include <linux/types.h>
+
+#ifdef CONFIG_FAULT_INJECTION_USERCOPY
+
+bool should_fail_usercopy(void);
+
+#else
+
+static inline bool should_fail_usercopy(void) { return false; }
+
+#endif /* CONFIG_FAULT_INJECTION_USERCOPY */
+
+#endif /* __LINUX_FAULT_INJECT_USERCOPY_H__ */
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index e068c3c7189a..2fc5049fba4e 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -1770,6 +1770,13 @@ config FAIL_PAGE_ALLOC
 	help
 	  Provide fault-injection capability for alloc_pages().
 
+config FAULT_INJECTION_USERCOPY
+	bool "Fault injection capability for usercopy functions"
+	depends on FAULT_INJECTION
+	help
+	  Provides fault-injection capability to inject failures
+	  in usercopy functions (copy_from_user(), get_user(), ...).
+
 config FAIL_MAKE_REQUEST
 	bool "Fault-injection capability for disk IO"
 	depends on FAULT_INJECTION && BLOCK
diff --git a/lib/Makefile b/lib/Makefile
index a4a4c6864f51..18daad2bc606 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -207,6 +207,7 @@ obj-$(CONFIG_AUDIT_COMPAT_GENERIC) += compat_audit.o
 
 obj-$(CONFIG_IOMMU_HELPER) += iommu-helper.o
 obj-$(CONFIG_FAULT_INJECTION) += fault-inject.o
+obj-$(CONFIG_FAULT_INJECTION_USERCOPY) += fault-inject-usercopy.o
 obj-$(CONFIG_NOTIFIER_ERROR_INJECTION) += notifier-error-inject.o
 obj-$(CONFIG_PM_NOTIFIER_ERROR_INJECT) += pm-notifier-error-inject.o
 obj-$(CONFIG_NETDEV_NOTIFIER_ERROR_INJECT) += netdev-notifier-error-inject.o
diff --git a/lib/fault-inject-usercopy.c b/lib/fault-inject-usercopy.c
new file mode 100644
index 000000000000..77558b6c29ca
--- /dev/null
+++ b/lib/fault-inject-usercopy.c
@@ -0,0 +1,39 @@
+// SPDX-License-Identifier: GPL-2.0-only
+#include <linux/fault-inject.h>
+#include <linux/fault-inject-usercopy.h>
+
+static struct {
+	struct fault_attr attr;
+} fail_usercopy = {
+	.attr = FAULT_ATTR_INITIALIZER,
+};
+
+static int __init setup_fail_usercopy(char *str)
+{
+	return setup_fault_attr(&fail_usercopy.attr, str);
+}
+__setup("fail_usercopy=", setup_fail_usercopy);
+
+#ifdef CONFIG_FAULT_INJECTION_DEBUG_FS
+
+static int __init fail_usercopy_debugfs(void)
+{
+	struct dentry *dir;
+
+	dir = fault_create_debugfs_attr("fail_usercopy", NULL,
+					&fail_usercopy.attr);
+	if (IS_ERR(dir))
+		return PTR_ERR(dir);
+
+	return 0;
+}
+
+late_initcall(fail_usercopy_debugfs);
+
+#endif /* CONFIG_FAULT_INJECTION_DEBUG_FS */
+
+bool should_fail_usercopy(void)
+{
+	return should_fail(&fail_usercopy.attr, 1);
+}
+EXPORT_SYMBOL_GPL(should_fail_usercopy);
-- 
2.28.0.402.g5ffc5be6b7-goog