From d32a21c4eec4897d04808e5ff0ac2dac46498231 Mon Sep 17 00:00:00 2001
From: Wim Taymans <wtaymans@redhat.com>
Date: Wed, 6 May 2026 11:29:20 +0200
Subject: [PATCH] rtp-sap: handle uninitialized avail

When the ioctl fails, avail might be uninitialized. Check the ioctl
return value and handle invalid avail.
---
 src/modules/module-rtp-sap.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/src/modules/module-rtp-sap.c b/src/modules/module-rtp-sap.c
index 290a34b51..97bedfb2a 100644
--- a/src/modules/module-rtp-sap.c
+++ b/src/modules/module-rtp-sap.c
@@ -591,13 +591,13 @@ static bool update_ts_refclk(struct impl *impl)
 			return false;
 	}
 
-	// Read if something is left in the socket
-	int avail;
+	int avail = 0;
 	uint8_t tmp;
 
-	ioctl(impl->ptp_fd, FIONREAD, &avail);
-	pw_log_debug("Flushing stale data: %u bytes", avail);
-	while (avail-- && read(impl->ptp_fd, &tmp, 1));
+	if (ioctl(impl->ptp_fd, FIONREAD, &avail) == 0 && avail > 0) {
+		pw_log_debug("Flushing stale data: %d bytes", avail);
+		while (avail-- > 0 && read(impl->ptp_fd, &tmp, 1) == 1);
+	}
 
 	struct ptp_management_msg req;
 	spa_zero(req);