From 33143b31800f3bfaaaea2ae857af9f01cd03fcf9 Mon Sep 17 00:00:00 2001
From: datenwolf <@datenwolf.net>
Date: Tue, 18 Jan 2022 01:04:49 +0100
Subject: deal with empty cmdline properly

---
 pmon.c | 18 +++++++++++-------
 1 file changed, 11 insertions(+), 7 deletions(-)

diff --git a/pmon.c b/pmon.c
index b7a5efa..f693550 100644
--- a/pmon.c
+++ b/pmon.c
@@ -19,10 +19,12 @@ static char* pid_cmdline(pid_t const pid)
 	snprintf(path, sizeof(path)-1, "/proc/%lu/cmdline", (long unsigned)pid);
 	FILE *fil = fopen(path, "r");
 	if( !fil ){ return NULL; }
-	size_t cmdlen = 0;
+	size_t cmdbuflen = 0;
 	char *cmdline = NULL;
-	getline(&cmdline, &cmdlen, fil);
+	ssize_t const cmdlen = getline(&cmdline, &cmdbuflen, fil);
+	fprintf(stderr, "cmdlen=%lu\n", (long unsigned)cmdlen);
 	fclose(fil);
+	if( !cmdbuflen || 0 >= cmdlen ){ free(cmdline); cmdline = NULL; }
 	return cmdline;
 }
 
@@ -121,11 +123,13 @@ static int handle_proc_ev(int nl_sock)
                 printf("set mcast listen ok\n");
                 break;
             case PROC_EVENT_FORK:
-                printf("fork: parent tid=%d pid=%d -> child tid=%d pid=%d\n",
-                        nlcn_msg.proc_ev.event_data.fork.parent_pid,
-                        nlcn_msg.proc_ev.event_data.fork.parent_tgid,
-                        nlcn_msg.proc_ev.event_data.fork.child_pid,
-                        nlcn_msg.proc_ev.event_data.fork.child_tgid);
+		cmdline = pid_cmdline(nlcn_msg.proc_ev.event_data.fork.parent_pid);
+                printf("fork: parent tid=%d pid=%d cmd='%s' -> child tid=%d pid=%d\n",
+                        (int)nlcn_msg.proc_ev.event_data.fork.parent_pid,
+                        (int)nlcn_msg.proc_ev.event_data.fork.parent_tgid,
+			cmdline,
+                        (int)nlcn_msg.proc_ev.event_data.fork.child_pid,
+                        (int)nlcn_msg.proc_ev.event_data.fork.child_tgid);
                 break;
             case PROC_EVENT_EXEC:
 		cmdline = pid_cmdline(nlcn_msg.proc_ev.event_data.exec.process_pid);
-- 
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