[LTP] [PATCH v15 1/2] futex_wake05: Add EFAULT error coverage test

[Michael Menasherov]

futex(FUTEX_WAKE) has no existing test for EFAULT. Add coverage for
unmapped, PROT_NONE, and kernel-space uaddr, each exercising a
different code path in the kernel's address validation.

Signed-off-by: Michael Menasherov <mmenashe@redhat.com>
---
 runtest/syscalls                              |   1 +
 testcases/kernel/syscalls/futex/.gitignore    |   1 +
 .../kernel/syscalls/futex/futex_wake05.c      | 101 ++++++++++++++++++
 3 files changed, 103 insertions(+)
 create mode 100644 testcases/kernel/syscalls/futex/futex_wake05.c

diff --git a/runtest/syscalls b/runtest/syscalls
index a021c79da..67509826f 100644
--- a/runtest/syscalls
+++ b/runtest/syscalls
@@ -1878,6 +1878,7 @@ futex_wake01 futex_wake01
 futex_wake02 futex_wake02
 futex_wake03 futex_wake03
 futex_wake04 futex_wake04
+futex_wake05 futex_wake05
 futex_wait_bitset01 futex_wait_bitset01
 
 memfd_create01 memfd_create01
diff --git a/testcases/kernel/syscalls/futex/.gitignore b/testcases/kernel/syscalls/futex/.gitignore
index 74ac9a926..c11546e07 100644
--- a/testcases/kernel/syscalls/futex/.gitignore
+++ b/testcases/kernel/syscalls/futex/.gitignore
@@ -15,3 +15,4 @@
 /futex_waitv03
 /futex_wait06
 /futex_wait07
+/futex_wake05
diff --git a/testcases/kernel/syscalls/futex/futex_wake05.c b/testcases/kernel/syscalls/futex/futex_wake05.c
new file mode 100644
index 000000000..162bc4e04
--- /dev/null
+++ b/testcases/kernel/syscalls/futex/futex_wake05.c
@@ -0,0 +1,101 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (C) 2026 Red Hat, Inc.
+ * Copyright (C) 2026 Michael Menasherov <mmenashe@redhat.com>
+ */
+
+/*\
+ * Check that futex(FUTEX_WAKE) returns EFAULT when uaddr points to
+ * unmapped, PROT_NONE, or kernel-space memory.
+ *
+ * For the unmapped and PROT_NONE cases, opflags=0 (no FUTEX_PRIVATE_FLAG)
+ * ensures futex_wake() takes the shared-futex path in get_futex_key()
+ * which must resolve the physical page. For PROT_NONE memory this page
+ * lookup fails with EFAULT, even though futex_wake() never reads *uaddr.
+ *
+ * The three cases exercise different code paths: a kernel-space address
+ * is rejected by the kernel's user-space address check before physical
+ * page resolution; unmapped memory fails at find_vma() (no VMA exists);
+ * PROT_NONE memory fails at get_user_pages_fast() (VMA exists but page
+ * is inaccessible).
+ */
+
+#include <errno.h>
+#include <sys/mman.h>
+
+#include "futextest.h"
+
+static futex_t *unmapped_addr;
+static futex_t *prot_none_addr;
+static futex_t *kernel_addr = (futex_t *)-1L;
+
+static struct futex_test_variants variants[] = {
+#if (__NR_futex != __LTP__NR_INVALID_SYSCALL)
+	{ .fntype = FUTEX_FN_FUTEX, .desc = "syscall with old kernel spec"},
+#endif
+
+#if (__NR_futex_time64 != __LTP__NR_INVALID_SYSCALL)
+	{ .fntype = FUTEX_FN_FUTEX64, .desc = "syscall time64 with kernel spec"},
+#endif
+};
+
+static struct testcase {
+	const char *desc;
+	futex_t **addr;
+	int exp_errno;
+} testcases[] = {
+	{
+		.desc = "uaddr unmapped",
+		.addr = &unmapped_addr,
+		.exp_errno = EFAULT,
+	},
+	{
+		.desc = "uaddr PROT_NONE",
+		.addr = &prot_none_addr,
+		.exp_errno = EFAULT,
+	},
+	{
+		.desc = "uaddr kernel address",
+		.addr = &kernel_addr,
+		.exp_errno = EFAULT,
+	},
+};
+
+static void run(unsigned int n)
+{
+	struct futex_test_variants *tv = &variants[tst_variant];
+	struct testcase *tc = &testcases[n];
+
+	TST_EXP_FAIL(futex_wake(tv->fntype, *tc->addr, 1, 0),
+		     tc->exp_errno, "%s", tc->desc);
+}
+
+static void setup(void)
+{
+	struct futex_test_variants *tv = &variants[tst_variant];
+	size_t pagesize = getpagesize();
+
+	tst_res(TINFO, "Testing variant: %s", tv->desc);
+	futex_supported_by_kernel(tv->fntype);
+
+	unmapped_addr = SAFE_MMAP(NULL, pagesize, PROT_READ | PROT_WRITE,
+				  MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
+	SAFE_MUNMAP((void *)unmapped_addr, pagesize);
+
+	prot_none_addr = SAFE_MMAP(NULL, pagesize, PROT_NONE,
+				   MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
+}
+
+static void cleanup(void)
+{
+	if (prot_none_addr)
+		SAFE_MUNMAP((void *)prot_none_addr, getpagesize());
+}
+
+static struct tst_test test = {
+	.setup = setup,
+	.cleanup = cleanup,
+	.test = run,
+	.tcnt = ARRAY_SIZE(testcases),
+	.test_variants = ARRAY_SIZE(variants),
+};
-- 
2.54.0