Author: google-labs-jules[bot] <161369871+google-labs-jules[bot]@users.noreply.github.com>
Date: Thu Sep 18 05:54:18 2025 +0100

Fix deletion worker communication protocol

The sai_deletion_worker was failing to delete old job directories
because the communication protocol over the pipe was not robust.
Directory names were written to the pipe without delimiters, causing the
worker to sometimes read multiple names concatenated together, leading
to invalid paths.

This commit fixes the protocol by:
1. Appending a newline character to each directory name written to the
   pipe in `scan_jobs_dir_cb`.
2. Implementing line-buffered reading in `sai_deletion_worker` to
   correctly parse the newline-delimited stream of directory names.

This ensures that the deletion worker processes one directory at a time,
even when deletion requests are sent in quick succession.


diff --git a/src/builder/b-sai.c b/src/builder/b-sai.c
index e6222f6..84f39f0 100644
--- a/src/builder/b-sai.c
+++ b/src/builder/b-sai.c
@@ -66,8 +66,9 @@ int getpid(void) { return 0; }
 static int
 sai_deletion_worker(const char *home_dir)
 {
-	char path[PATH_MAX], *p;
-	ssize_t n;
+	char *p, line[PATH_MAX], buf[4096];
+	ssize_t n, len = 0;
+	char *nl;
 
 	lwsl_notice("%s: deletion worker started\n", __func__);
 
@@ -80,41 +81,51 @@ sai_deletion_worker(const char *home_dir)
 	FreeConsole();
 #endif
 
-	while (1) {
-		n = read(0, path, sizeof(path) - 1);
-
+	do {
+		n = read(0, buf + len, (sizeof(buf) - 1) - (unsigned int)len);
 		if (n <= 0) {
 			lwsl_notice("%s: pipe closed, exiting\n", __func__);
 			return 0;
 		}
+		len += n;
 
-		path[n] = '\0';
-		p = path;
-
-		/* sanitize: no .. or / or \ */
-		while (*p) {
-			if (*p == '.' || *p == '/' || *p == '\\') {
-				lwsl_err("%s: invalid chars in delete path '%s'\n",
-					 __func__, path);
-				p = NULL;
+		do {
+			nl = memchr(buf, '\n', (unsigned int)len);
+			if (!nl)
 				break;
+
+			*nl = '\0';
+			lws_strncpy(line, buf, sizeof(line));
+
+			len -= (nl - buf) + 1;
+			memmove(buf, nl + 1, (unsigned int)len);
+
+			p = line;
+			/* sanitize: no .. or / or \ */
+			while (*p) {
+				if (*p == '.' || *p == '/' || *p == '\\') {
+					lwsl_err("%s: invalid chars in delete path '%s'\n",
+						 __func__, line);
+					p = NULL;
+					break;
+				}
+				p++;
 			}
-			p++;
-		}
-		if (!p)
-			continue;
+			if (!p)
+				continue;
 
-		{
-			char full_path[PATH_MAX];
+			{
+				char full_path[PATH_MAX];
+				lws_snprintf(full_path, sizeof(full_path),
+					     "%s/jobs/%s", home_dir, line);
 
-			lws_snprintf(full_path, sizeof(full_path), "%s/jobs/%s",
-				     home_dir, path);
+				if (lws_dir(full_path, NULL, lws_dir_rm_rf_cb))
+					lwsl_err("%s: failed to delete %s\n",
+						 __func__, full_path);
+			}
+		} while (1);
 
-			if (lws_dir(full_path, NULL, lws_dir_rm_rf_cb))
-				lwsl_err("%s: failed to delete %s\n", __func__,
-					 full_path);
-		}
-	}
+	} while (1);
 
 	return 0;
 }
@@ -166,15 +177,22 @@ scan_jobs_dir_cb(const char *dirpath, void *user, struct lws_dir_entry *lde)
 		lwsl_notice("%s: requesting removal of old job dir %s\n",
 			    __func__, path);
 #if !defined(WIN32)
-		if (write(builder.pipe_master_wr, lde->name,
-			  LWS_POSIX_LENGTH_CAST(strlen(lde->name))) != (ssize_t)strlen(lde->name))
-			lwsl_err("%s: failed to write to deletion worker\n",
-				 __func__);
+		{
+			char temp[128];
+			int len = lws_snprintf(temp, sizeof(temp), "%s\n", lde->name);
+
+			if (write(builder.pipe_master_wr, temp, (unsigned int)len) != len)
+				lwsl_err("%s: failed to write to deletion worker\n",
+					 __func__);
+		}
 #else
 		{
+			char temp[128];
+			int len = lws_snprintf(temp, sizeof(temp), "%s\n", lde->name);
 			DWORD written;
-			if (!WriteFile(builder.pipe_master_wr_win, lde->name,
-				       (DWORD)strlen(lde->name), &written, NULL))
+
+			if (!WriteFile(builder.pipe_master_wr_win, temp, (DWORD)len,
+				       &written, NULL) || written != (DWORD)len)
 				lwsl_err("%s: failed to write to deletion worker\n",
 					 __func__);
 		}
diff --git a/src/builder/b-task.c b/src/builder/b-task.c
index d31f23b..4a4c5cf 100644
--- a/src/builder/b-task.c
+++ b/src/builder/b-task.c
@@ -412,7 +412,7 @@ saib_task_destroy(struct sai_nspawn *ns)
 		{
 			DWORD written;
 			if (!WriteFile(builder.pipe_master_wr_win, ns->task->uuid,
-				       strlen(ns->task->uuid), &written, NULL))
+				       (DWORD)strlen(ns->task->uuid), &written, NULL))
 				lwsl_err("%s: failed to write to deletion worker\n",
 					 __func__);
 		}