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Message-ID: <b452aeac-9628-5e37-e0e6-d33f8bb47b22@sberdevices.ru>
Date: Tue, 15 Mar 2022 09:34:35 +0000
From: Krasnov Arseniy Vladimirovich <AVKrasnov@...rdevices.ru>
To: Stefano Garzarella <sgarzare@...hat.com>
CC: Krasnov Arseniy <oxffffaa@...il.com>,
Rokosov Dmitry Dmitrievich <DDRokosov@...rdevices.ru>,
"kvm@...r.kernel.org" <kvm@...r.kernel.org>,
"virtualization@...ts.linux-foundation.org"
<virtualization@...ts.linux-foundation.org>,
"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH v1 3/3] af_vsock: SOCK_SEQPACKET broken buffer test
On 15.03.2022 11:36, Stefano Garzarella wrote:
> 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@...rdevices.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()
Ack, fix it in v2
>
>> + exit(EXIT_FAILURE);
>> + }
>> +
>> + if (errno != ENOMEM) {
>> + perror("invalid errno of 'broken_buf'");
>
> Instead of "invalid", I would say "unexpected".
Ack
>
>> + 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.
Ack
>
>> + 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, ...)
Ack
>
>> + exit(EXIT_FAILURE);
>> + }
>> + }
>
> What about replace this for with a memcmp()?
Ack
>
>> +
>> +
>> + /* 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?
I've just checked AF_UNIX implementation of SEQPACKET receive in net/unix/af_unix.c. So, if 'skb_copy_datagram_msg()'
fails, it calls 'skb_free_datagram()'. I think this means that whole sk buff will be dropped, but anyway, i'll check
this behaviour in practice. See '__unix_dgram_recvmsg()' in net/unix/af_unix.c.
>
> Thanks,
> Stefano
>
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