linux-kernel - [PATCH v1] tools/hv: terminate fcopy daemon if read from uio fails

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Message-ID: <20241025143009.4571-1-olaf@aepfle.de>
Date: Fri, 25 Oct 2024 16:28:27 +0200
From: Olaf Hering <olaf@...fle.de>
To: linux-hyperv@...r.kernel.org,
	linux-kernel@...r.kernel.org
Cc: "K. Y. Srinivasan" <kys@...rosoft.com>,
	Haiyang Zhang <haiyangz@...rosoft.com>,
	Wei Liu <wei.liu@...nel.org>,
	Dexuan Cui <decui@...rosoft.com>
Subject: [PATCH v1] tools/hv: terminate fcopy daemon if read from uio fails

Terminate endless loop in reading fails, to avoid flooding syslog.

This happens if the "Guest services" integration service is
disabled at runtime in the VM settings.

Also handle an interrupted system call, and continue in this case.

Signed-off-by: Olaf Hering <olaf@...fle.de>
---

A more complete fix is to handle this properly in the kernel,
by making the file descriptor unavailable for further operations.

 tools/hv/hv_fcopy_uio_daemon.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/tools/hv/hv_fcopy_uio_daemon.c b/tools/hv/hv_fcopy_uio_daemon.c
index 7a00f3066a98..281fd95dc0d8 100644
--- a/tools/hv/hv_fcopy_uio_daemon.c
+++ b/tools/hv/hv_fcopy_uio_daemon.c
@@ -468,8 +468,10 @@ int main(int argc, char *argv[])
 		 */
 		ret = pread(fcopy_fd, &tmp, sizeof(int), 0);
 		if (ret < 0) {
+			if (errno == EINTR || errno == EAGAIN)
+				continue;
 			syslog(LOG_ERR, "pread failed: %s", strerror(errno));
-			continue;
+			goto close;
 		}
 
 		len = HV_RING_SIZE;