linux-kernel - [PATCH v7 2/2] KVM: selftests: update guest

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <20251114151828.98165-3-kalyazin@amazon.com>
Date: Fri, 14 Nov 2025 15:18:53 +0000
From: "Kalyazin, Nikita" <kalyazin@...zon.co.uk>
To: "pbonzini@...hat.com" <pbonzini@...hat.com>, "shuah@...nel.org"
	<shuah@...nel.org>
CC: "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
	"linux-kselftest@...r.kernel.org" <linux-kselftest@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"seanjc@...gle.com" <seanjc@...gle.com>, "david@...nel.org"
	<david@...nel.org>, "jthoughton@...gle.com" <jthoughton@...gle.com>,
	"ackerleytng@...gle.com" <ackerleytng@...gle.com>, "vannapurve@...gle.com"
	<vannapurve@...gle.com>, "jackmanb@...gle.com" <jackmanb@...gle.com>,
	"patrick.roy@...ux.dev" <patrick.roy@...ux.dev>, "Thomson, Jack"
	<jackabt@...zon.co.uk>, "Itazuri, Takahiro" <itazur@...zon.co.uk>,
	"Manwaring, Derek" <derekmn@...zon.com>, "Cali, Marco"
	<xmarcalx@...zon.co.uk>, "Kalyazin, Nikita" <kalyazin@...zon.co.uk>
Subject: [PATCH v7 2/2] KVM: selftests: update guest_memfd write tests

From: Nikita Kalyazin <kalyazin@...zon.com>

This is to reflect that the write syscall is now implemented for
guest_memfd.

Signed-off-by: Nikita Kalyazin <kalyazin@...zon.com>
---
 .../testing/selftests/kvm/guest_memfd_test.c  | 58 +++++++++++++++++--
 1 file changed, 52 insertions(+), 6 deletions(-)

diff --git a/tools/testing/selftests/kvm/guest_memfd_test.c b/tools/testing/selftests/kvm/guest_memfd_test.c
index e7d9aeb418d3..ef3e92e18ee6 100644
--- a/tools/testing/selftests/kvm/guest_memfd_test.c
+++ b/tools/testing/selftests/kvm/guest_memfd_test.c
@@ -24,18 +24,57 @@
 
 static size_t page_size;
 
-static void test_file_read_write(int fd, size_t total_size)
+static void test_file_read(int fd, size_t total_size)
 {
 	char buf[64];
 
 	TEST_ASSERT(read(fd, buf, sizeof(buf)) < 0,
 		    "read on a guest_mem fd should fail");
-	TEST_ASSERT(write(fd, buf, sizeof(buf)) < 0,
-		    "write on a guest_mem fd should fail");
 	TEST_ASSERT(pread(fd, buf, sizeof(buf), 0) < 0,
 		    "pread on a guest_mem fd should fail");
-	TEST_ASSERT(pwrite(fd, buf, sizeof(buf), 0) < 0,
-		    "pwrite on a guest_mem fd should fail");
+}
+
+static void test_write_supported(int fd, size_t total_size)
+{
+	size_t page_size = getpagesize();
+	void *buf = NULL;
+	int ret;
+
+	ret = posix_memalign(&buf, page_size, total_size);
+	TEST_ASSERT_EQ(ret, 0);
+
+	ret = pwrite(fd, buf, page_size, total_size);
+	TEST_ASSERT(ret == -1, "writing past the file size on a guest_mem fd should fail");
+	TEST_ASSERT_EQ(errno, EINVAL);
+
+	ret = pwrite(fd, buf, 1, 0);
+	TEST_ASSERT(ret == -1, "writing an unaligned count a guest_mem fd should fail");
+	TEST_ASSERT_EQ(errno, EINVAL);
+
+	ret = pwrite(fd, buf, page_size, 1);
+	TEST_ASSERT(ret == -1, "writing to an unaligned offset a guest_mem fd should fail");
+	TEST_ASSERT_EQ(errno, EINVAL);
+
+	ret = pwrite(fd, buf, page_size, 0);
+	TEST_ASSERT(ret == page_size, "write on a guest_mem fd should succeed");
+
+	free(buf);
+}
+
+static void test_write_not_supported(int fd, size_t total_size)
+{
+	size_t page_size = getpagesize();
+	void *buf = NULL;
+	int ret;
+
+	ret = posix_memalign(&buf, page_size, total_size);
+	TEST_ASSERT_EQ(ret, 0);
+
+	ret = pwrite(fd, buf, page_size, 0);
+	TEST_ASSERT(ret == -1, "write on guest_mem fd should fail");
+	TEST_ASSERT_EQ(errno, ENODEV);
+
+	free(buf);
 }
 
 static void test_mmap_cow(int fd, size_t size)
@@ -267,7 +306,7 @@ static void __test_guest_memfd(struct kvm_vm *vm, uint64_t flags)
 	test_create_guest_memfd_multiple(vm);
 	test_create_guest_memfd_invalid_sizes(vm, flags);
 
-	gmem_test(file_read_write, vm, flags);
+	gmem_test(file_read, vm, flags);
 
 	if (flags & GUEST_MEMFD_FLAG_MMAP) {
 		if (flags & GUEST_MEMFD_FLAG_INIT_SHARED) {
@@ -282,6 +321,11 @@ static void __test_guest_memfd(struct kvm_vm *vm, uint64_t flags)
 		gmem_test(mmap_not_supported, vm, flags);
 	}
 
+	if (flags & GUEST_MEMFD_FLAG_WRITE)
+		gmem_test(write_supported, vm, flags);
+	else
+		gmem_test(write_not_supported, vm, flags);
+
 	gmem_test(file_size, vm, flags);
 	gmem_test(fallocate, vm, flags);
 	gmem_test(invalid_punch_hole, vm, flags);
@@ -299,6 +343,8 @@ static void test_guest_memfd(unsigned long vm_type)
 	flags = vm_check_cap(vm, KVM_CAP_GUEST_MEMFD_FLAGS);
 	if (flags & GUEST_MEMFD_FLAG_MMAP)
 		__test_guest_memfd(vm, GUEST_MEMFD_FLAG_MMAP);
+	if (flags & GUEST_MEMFD_FLAG_WRITE)
+		__test_guest_memfd(vm, GUEST_MEMFD_FLAG_WRITE);
 
 	/* MMAP should always be supported if INIT_SHARED is supported. */
 	if (flags & GUEST_MEMFD_FLAG_INIT_SHARED)
-- 
2.50.1