From: Stefano Garzarella <sgarzare@redhat.com>

When send() or recv() returns -1 with errno == EINTR, the code skips
the break but still adds the return value to nwritten/nread, making it
decrease by 1. This leads to wrong buffer offsets and wrong bytes count.

Fix it by explicitly continuing the loop on EINTR, so the return value
is only added when it is positive.

Fixes: a8ed71a27ef5 ("vsock/test: add recv_buf() utility function")
Fixes: 12329bd51fdc ("vsock/test: add send_buf() utility function")
Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
---
 tools/testing/vsock/util.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/tools/testing/vsock/util.c b/tools/testing/vsock/util.c
index 9430ef5b8bc3..1fe1338c79cd 100644
--- a/tools/testing/vsock/util.c
+++ b/tools/testing/vsock/util.c
@@ -344,7 +344,9 @@ void send_buf(int fd, const void *buf, size_t len, int flags,
 		ret = send(fd, buf + nwritten, len - nwritten, flags);
 		timeout_check("send");
 
-		if (ret == 0 || (ret < 0 && errno != EINTR))
+		if (ret < 0 && errno == EINTR)
+			continue;
+		if (ret <= 0)
 			break;
 
 		nwritten += ret;
@@ -396,7 +398,9 @@ void recv_buf(int fd, void *buf, size_t len, int flags, ssize_t expected_ret)
 		ret = recv(fd, buf + nread, len - nread, flags);
 		timeout_check("recv");
 
-		if (ret == 0 || (ret < 0 && errno != EINTR))
+		if (ret < 0 && errno == EINTR)
+			continue;
+		if (ret <= 0)
 			break;
 
 		nread += ret;
-- 
2.53.0

On Fri, Apr 03, 2026 at 11:32:51AM +0200, Stefano Garzarella wrote:
>From: Stefano Garzarella <sgarzare@redhat.com>
>
>When send() or recv() returns -1 with errno == EINTR, the code skips
>the break but still adds the return value to nwritten/nread, making it
>decrease by 1. This leads to wrong buffer offsets and wrong bytes count.
>
>Fix it by explicitly continuing the loop on EINTR, so the return value
>is only added when it is positive.
>
>Fixes: a8ed71a27ef5 ("vsock/test: add recv_buf() utility function")
>Fixes: 12329bd51fdc ("vsock/test: add send_buf() utility function")
>Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
>---
> tools/testing/vsock/util.c | 8 ++++++--
> 1 file changed, 6 insertions(+), 2 deletions(-)
>
>diff --git a/tools/testing/vsock/util.c b/tools/testing/vsock/util.c
>index 9430ef5b8bc3..1fe1338c79cd 100644
>--- a/tools/testing/vsock/util.c
>+++ b/tools/testing/vsock/util.c
>@@ -344,7 +344,9 @@ void send_buf(int fd, const void *buf, size_t len, int flags,
> 		ret = send(fd, buf + nwritten, len - nwritten, flags);
> 		timeout_check("send");
>
>-		if (ret == 0 || (ret < 0 && errno != EINTR))
>+		if (ret < 0 && errno == EINTR)
>+			continue;
>+		if (ret <= 0)
> 			break;
>
> 		nwritten += ret;
>@@ -396,7 +398,9 @@ void recv_buf(int fd, void *buf, size_t len, int flags, ssize_t expected_ret)
> 		ret = recv(fd, buf + nread, len - nread, flags);
> 		timeout_check("recv");
>
>-		if (ret == 0 || (ret < 0 && errno != EINTR))
>+		if (ret < 0 && errno == EINTR)
>+			continue;
>+		if (ret <= 0)
> 			break;
>
> 		nread += ret;
>-- 
>2.53.0
>

LGTM!

Reviewed-by: Luigi Leonardi <leonardi@redhat.com>