Merge tag 'copy-struct-from-user-v5.4-rc4' of...

Merge tag 'copy-struct-from-user-v5.4-rc4' of gitolite.kernel.org:pub/scm/linux/kernel/git/brauner/linux

Pull usercopy test fixlets from Christian Brauner:
 "This contains two improvements for the copy_struct_from_user() tests:

   - a coding style change to get rid of the ugly "if ((ret |= test()))"
     pointed out when pulling the original patchset.

   - avoid a soft lockups when running the usercopy tests on machines
     with large page sizes by scanning only a 1024 byte region"

* tag 'copy-struct-from-user-v5.4-rc4' of gitolite.kernel.org:pub/scm/linux/kernel/git/brauner/linux:
  usercopy: Avoid soft lockups in test_check_nonzero_user()
  lib: test_user_copy: style cleanup

lib/test_user_copy.c

@@ -47,18 +47,35 @@ static bool is_zeroed(void *from, size_t size)
 static int test_check_nonzero_user(char *kmem, char __user *umem, size_t size)
 {
 	int ret = 0;
-	size_t start, end, i;
-	size_t zero_start = size / 4;
-	size_t zero_end = size - zero_start;
+	size_t start, end, i, zero_start, zero_end;
+
+	if (test(size < 2 * PAGE_SIZE, "buffer too small"))
+		return -EINVAL;
+
+	/*
+	 * We want to cross a page boundary to exercise the code more
+	 * effectively. We also don't want to make the size we scan too large,
+	 * otherwise the test can take a long time and cause soft lockups. So
+	 * scan a 1024 byte region across the page boundary.
+	 */
+	size = 1024;
+	start = PAGE_SIZE - (size / 2);
+
+	kmem += start;
+	umem += start;
+
+	zero_start = size / 4;
+	zero_end = size - zero_start;
 
 	/*
-	 * We conduct a series of check_nonzero_user() tests on a block of memory
-	 * with the following byte-pattern (trying every possible [start,end]
-	 * pair):
+	 * We conduct a series of check_nonzero_user() tests on a block of
+	 * memory with the following byte-pattern (trying every possible
+	 * [start,end] pair):
 	 *
 	 *   [ 00 ff 00 ff ... 00 00 00 00 ... ff 00 ff 00 ]
 	 *
-	 * And we verify that check_nonzero_user() acts identically to memchr_inv().
+	 * And we verify that check_nonzero_user() acts identically to
+	 * memchr_inv().
 	 */
 
 	memset(kmem, 0x0, size);
@@ -93,11 +110,13 @@ static int test_copy_struct_from_user(char *kmem, char __user *umem,
 	size_t ksize, usize;
 
 	umem_src = kmalloc(size, GFP_KERNEL);
-	if ((ret |= test(umem_src == NULL, "kmalloc failed")))
+	ret = test(umem_src == NULL, "kmalloc failed");
+	if (ret)
 		goto out_free;
 
 	expected = kmalloc(size, GFP_KERNEL);
-	if ((ret |= test(expected == NULL, "kmalloc failed")))
+	ret = test(expected == NULL, "kmalloc failed");
+	if (ret)
 		goto out_free;
 
 	/* Fill umem with a fixed byte pattern. */