[PATCH v2 08/11] test_user_copy: Check __clear_user()/clear_user()

[James Hogan]

Add basic success/failure checking of __clear_user() and clear_user(),
which zero an area of user or kernel memory and return the number of
bytes left to clear.

This catches a couple of bugs in the MIPS Enhanced Virtual Memory (EVA)
implementation (which have already been fixed):
test_user_copy: legitimate kernel clear_user failed
test_user_copy: legitimate kernel __clear_user failed

Due to neither function checking the user address limit, and both
resorting to user access unconditionally.

New tests:
- legitimate clear_user
- legitimate __clear_user
- illegal kernel clear_user
- illegal kernel __clear_user
- legitimate kernel clear_user
- legitimate kernel __clear_user

Signed-off-by: James Hogan <james.hogan@xxxxxxxxxx>
Acked-by: Kees Cook <keescook@xxxxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
 lib/test_user_copy.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/lib/test_user_copy.c b/lib/test_user_copy.c
index c002fc1286bd..450b4c379c61 100644
--- a/lib/test_user_copy.c
+++ b/lib/test_user_copy.c
@@ -68,6 +68,8 @@ static int __init test_user_copy_init(void)
 		    "legitimate get_user failed");
 	ret |= test(put_user(value, (unsigned long __user *)usermem),
 		    "legitimate put_user failed");
+	ret |= test(clear_user(usermem, PAGE_SIZE) != 0,
+		    "legitimate clear_user passed");
 
 	ret |= test(!access_ok(VERIFY_READ, usermem, PAGE_SIZE * 2),
 		    "legitimate access_ok VERIFY_READ failed");
@@ -85,6 +87,8 @@ static int __init test_user_copy_init(void)
 		    "legitimate __get_user failed");
 	ret |= test(__put_user(value, (unsigned long __user *)usermem),
 		    "legitimate __put_user failed");
+	ret |= test(__clear_user(usermem, PAGE_SIZE) != 0,
+		    "legitimate __clear_user passed");
 
 	/* Invalid usage: none of these should succeed. */
 	ret |= test(!copy_from_user(kmem, (char __user *)(kmem + PAGE_SIZE),
@@ -103,6 +107,8 @@ static int __init test_user_copy_init(void)
 		    "illegal get_user passed");
 	ret |= test(!put_user(value, (unsigned long __user *)kmem),
 		    "illegal put_user passed");
+	ret |= test(clear_user((char __user *)kmem, PAGE_SIZE) != PAGE_SIZE,
+		    "illegal kernel clear_user passed");
 
 	/*
 	 * If unchecked user accesses (__*) on this architecture cannot access
@@ -145,6 +151,8 @@ static int __init test_user_copy_init(void)
 		    "illegal __get_user passed");
 	ret |= test(!__put_user(value, (unsigned long __user *)kmem),
 		    "illegal __put_user passed");
+	ret |= test(__clear_user((char __user *)kmem, PAGE_SIZE) != PAGE_SIZE,
+		    "illegal kernel __clear_user passed");
 #endif
 
 	/*
@@ -165,6 +173,8 @@ static int __init test_user_copy_init(void)
 		    "legitimate kernel get_user failed");
 	ret |= test(put_user(value, (unsigned long __user *)kmem),
 		    "legitimate kernel put_user failed");
+	ret |= test(clear_user((char __user *)kmem, PAGE_SIZE) != 0,
+		    "legitimate kernel clear_user failed");
 
 	ret |= test(!access_ok(VERIFY_READ, (char __user *)kmem, PAGE_SIZE * 2),
 		    "legitimate kernel access_ok VERIFY_READ failed");
@@ -188,6 +198,8 @@ static int __init test_user_copy_init(void)
 		    "legitimate kernel __get_user failed");
 	ret |= test(__put_user(value, (unsigned long __user *)kmem),
 		    "legitimate kernel __put_user failed");
+	ret |= test(__clear_user((char __user *)kmem, PAGE_SIZE) != 0,
+		    "legitimate kernel __clear_user failed");
 
 	/* Restore previous address limit. */
 	set_fs(fs);
-- 
2.3.6

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