Virtualization - Mar 2022 - [RFC PATCH v1 3/3] af_vsock: SOCK_SEQPACKET broken buffer test

On Fri, Mar 11, 2022 at 10:58:32AM +0000, Krasnov Arseniy Vladimirovich
wrote:
>Add test where sender sends two message, each with own
>data pattern. Reader tries to read first to broken buffer:
>it has three pages size, but middle page is unmapped. Then,
>reader tries to read second message to valid buffer. Test
>checks, that uncopied part of first message was dropped
>and thus not copied as part of second message.
>
>Signed-off-by: Arseniy Krasnov <AVKrasnov at sberdevices.ru>
>---
> tools/testing/vsock/vsock_test.c | 121 +++++++++++++++++++++++++++++++
> 1 file changed, 121 insertions(+)
>
>diff --git a/tools/testing/vsock/vsock_test.c
b/tools/testing/vsock/vsock_test.c
>index aa2de27d0f77..686af712b4ad 100644
>--- a/tools/testing/vsock/vsock_test.c
>+++ b/tools/testing/vsock/vsock_test.c
>@@ -16,6 +16,7 @@
> #include <linux/kernel.h>
> #include <sys/types.h>
> #include <sys/socket.h>
>+#include <sys/mman.h>
>
> #include "timeout.h"
> #include "control.h"
>@@ -435,6 +436,121 @@ static void test_seqpacket_timeout_server(const struct
test_opts *opts)
> 	close(fd);
> }
>
>+#define BUF_PATTERN_1 'a'
>+#define BUF_PATTERN_2 'b'
>+
>+static void test_seqpacket_invalid_rec_buffer_client(const struct test_opts
*opts)
>+{
>+	int fd;
>+	unsigned char *buf1;
>+	unsigned char *buf2;
>+	int buf_size = getpagesize() * 3;
>+
>+	fd = vsock_seqpacket_connect(opts->peer_cid, 1234);
>+	if (fd < 0) {
>+		perror("connect");
>+		exit(EXIT_FAILURE);
>+	}
>+
>+	buf1 = malloc(buf_size);
>+	if (buf1 == NULL) {
>+		perror("'malloc()' for 'buf1'");
>+		exit(EXIT_FAILURE);
>+	}
>+
>+	buf2 = malloc(buf_size);
>+	if (buf2 == NULL) {
>+		perror("'malloc()' for 'buf2'");
>+		exit(EXIT_FAILURE);
>+	}
>+
>+	memset(buf1, BUF_PATTERN_1, buf_size);
>+	memset(buf2, BUF_PATTERN_2, buf_size);
>+
>+	if (send(fd, buf1, buf_size, 0) != buf_size) {
>+		perror("send failed");
>+		exit(EXIT_FAILURE);
>+	}
>+
>+	if (send(fd, buf2, buf_size, 0) != buf_size) {
>+		perror("send failed");
>+		exit(EXIT_FAILURE);
>+	}
>+
>+	close(fd);
>+}
>+
>+static void test_seqpacket_invalid_rec_buffer_server(const struct test_opts
*opts)
>+{
>+	int fd;
>+	unsigned char *broken_buf;
>+	unsigned char *valid_buf;
>+	int page_size = getpagesize();
>+	int buf_size = page_size * 3;
>+	ssize_t res;
>+	int prot = PROT_READ | PROT_WRITE;
>+	int flags = MAP_PRIVATE | MAP_ANONYMOUS;
>+	int i;
>+
>+	fd = vsock_seqpacket_accept(VMADDR_CID_ANY, 1234, NULL);
>+	if (fd < 0) {
>+		perror("accept");
>+		exit(EXIT_FAILURE);
>+	}
>+
>+	/* Setup first buffer. */
>+	broken_buf = mmap(NULL, buf_size, prot, flags, -1, 0);
>+	if (broken_buf == MAP_FAILED) {
>+		perror("mmap for 'broken_buf'");
>+		exit(EXIT_FAILURE);
>+	}
>+
>+	/* Unmap "hole" in buffer. */
>+	if (munmap(broken_buf + page_size, page_size)) {
>+		perror("'broken_buf' setup");
>+		exit(EXIT_FAILURE);
>+	}
>+
>+	valid_buf = mmap(NULL, buf_size, prot, flags, -1, 0);
>+	if (valid_buf == MAP_FAILED) {
>+		perror("mmap for 'valid_buf'");
>+		exit(EXIT_FAILURE);
>+	}
>+
>+	/* Try to fill buffer with unmapped middle. */
>+	res = read(fd, broken_buf, buf_size);
>+	if (res != -1) {
>+		perror("invalid read result of 'broken_buf'");
if `res` is valid, errno is not set, better to use fprintf(stderr, ...) 
printing the expected and received result.
Take a look at test_stream_connection_reset()
>+		exit(EXIT_FAILURE);
>+	}
>+
>+	if (errno != ENOMEM) {
>+		perror("invalid errno of 'broken_buf'");
Instead of "invalid", I would say "unexpected".
>+		exit(EXIT_FAILURE);
>+	}
>+
>+	/* Try to fill valid buffer. */
>+	res = read(fd, valid_buf, buf_size);
>+	if (res != buf_size) {
>+		perror("invalid read result of 'valid_buf'");
I would split in 2 checks:
- (res < 0) then use perror()
- (res != buf_size) then use fprintf(stderr, ...) printing the expected 
   and received result.
>+		exit(EXIT_FAILURE);
>+	}
>+
>+	for (i = 0; i < buf_size; i++) {
>+		if (valid_buf[i] != BUF_PATTERN_2) {
>+			perror("invalid pattern for valid buf");
errno is not set here, better to use fprintf(stderr, ...)
>+			exit(EXIT_FAILURE);
>+		}
>+	}
What about replace this for with a memcmp()?
>+
>+
>+	/* Unmap buffers. */
>+	munmap(broken_buf, page_size);
>+	munmap(broken_buf + page_size * 2, page_size);
>+	munmap(valid_buf, buf_size);
>+	close(fd);
>+}
>+
> static struct test_case test_cases[] = {
> 	{
> 		.name = "SOCK_STREAM connection reset",
>@@ -480,6 +596,11 @@ static struct test_case test_cases[] = {
> 		.run_client = test_seqpacket_timeout_client,
> 		.run_server = test_seqpacket_timeout_server,
> 	},
>+	{
>+		.name = "SOCK_SEQPACKET invalid receive buffer",
>+		.run_client = test_seqpacket_invalid_rec_buffer_client,
>+		.run_server = test_seqpacket_invalid_rec_buffer_server,
>+	},

Is this the right behavior? If read() fails because the buffer is 
invalid, do we throw out the whole packet?

I was expecting the packet not to be consumed, have you tried AF_UNIX, 
does it have the same behavior?

Thanks,
Stefano