From 6386d192442cac2fd58bc1f8111dabe84ce6baf5 Mon Sep 17 00:00:00 2001
From: =?utf8?q?Eivind=20N=C3=A6ss?= <eivnaes@yahoo.com>
Date: Mon, 20 Sep 2021 09:29:21 -0700
Subject: [PATCH] Fixing main.c with regards to default GCC/CLANG compiler
 warnings
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This also incorporates the comments from @paulusmack.

Generally, fixes:
- Suppresed warnings w.r.t. unused results in signal handling and result from write()
- Unused results w.r.t. setuid/getuid/chdir

Signed-off-by: Eivind Næss <eivnaes@yahoo.com>
---
 pppd/main.c | 63 ++++++++++++++++++++++++++++++++++++++++-------------
 1 file changed, 48 insertions(+), 15 deletions(-)

diff --git a/pppd/main.c b/pppd/main.c
index 203202f..b1ac8b4 100644
--- a/pppd/main.c
+++ b/pppd/main.c
@@ -753,6 +753,7 @@ void
 detach(void)
 {
     int pid;
+    int ret;
     char numbuf[16];
     int pipefd[2];
 
@@ -774,7 +775,10 @@ detach(void)
 	exit(0);		/* parent dies */
     }
     setsid();
-    chdir("/");
+    ret = chdir("/");
+    if (ret != 0) {
+        fatal("Could not change directory to '/', %m");
+    }
     dup2(fd_devnull, 0);
     dup2(fd_devnull, 1);
     dup2(fd_devnull, 2);
@@ -1413,8 +1417,12 @@ hup(int sig)
 	/* Send the signal to the [dis]connector process(es) also */
 	kill_my_pg(sig);
     notify(sigreceived, sig);
-    if (waiting)
+    if (waiting) {
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wunused-result"
 	write(sigpipe[1], &sig, sizeof(sig));
+#pragma GCC diagnostic pop
+    }
 }
 
 
@@ -1433,8 +1441,12 @@ term(int sig)
 	/* Send the signal to the [dis]connector process(es) also */
 	kill_my_pg(sig);
     notify(sigreceived, sig);
-    if (waiting)
+    if (waiting) {
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wunused-result"
 	write(sigpipe[1], &sig, sizeof(sig));
+#pragma GCC diagnostic pop
+    }
 }
 
 
@@ -1446,8 +1458,12 @@ static void
 chld(int sig)
 {
     got_sigchld = 1;
-    if (waiting)
+    if (waiting) {
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wunused-result"
 	write(sigpipe[1], &sig, sizeof(sig));
+#pragma GCC diagnostic pop
+    }
 }
 
 
@@ -1479,8 +1495,12 @@ static void
 open_ccp(int sig)
 {
     got_sigusr2 = 1;
-    if (waiting)
+    if (waiting) {
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wunused-result"
 	write(sigpipe[1], &sig, sizeof(sig));
+#pragma GCC diagnostic pop
+    }
 }
 
 
@@ -1642,6 +1662,7 @@ device_script(char *program, int in, int out, int dont_wait)
     int pid;
     int status = -1;
     int errfd;
+    int ret;
 
     if (log_to_fd >= 0)
 	errfd = log_to_fd;
@@ -1676,12 +1697,15 @@ device_script(char *program, int in, int out, int dont_wait)
     }
 
     /* here we are executing in the child */
-
-    setgid(getgid());
-    setuid(uid);
-    if (getuid() != uid) {
-	fprintf(stderr, "pppd: setuid failed\n");
-	exit(1);
+    ret = setgid(getgid());
+    if (ret != 0) {
+        perror("pppd: setgid failed\n");
+        exit(1);
+    }
+    ret = setuid(uid);
+    if (ret != 0 || getuid() != uid) {
+        perror("pppd: setuid failed\n");
+        exit(1);
     }
     update_system_environment();
     execl("/bin/sh", "sh", "-c", program, (char *)0);
@@ -1742,7 +1766,7 @@ update_script_environment(void)
 pid_t
 run_program(char *prog, char **args, int must_exist, void (*done)(void *), void *arg, int wait)
 {
-    int pid, status;
+    int pid, status, ret;
     struct stat sbuf;
 
     /*
@@ -1782,9 +1806,18 @@ run_program(char *prog, char **args, int must_exist, void (*done)(void *), void
     /* Leave the current location */
     (void) setsid();	/* No controlling tty. */
     (void) umask (S_IRWXG|S_IRWXO);
-    (void) chdir ("/");	/* no current directory. */
-    setuid(0);		/* set real UID = root */
-    setgid(getegid());
+    ret = chdir ("/");	/* no current directory. */
+    if (ret != 0) {
+        fatal("Failed to change directory to '/', %m");
+    }
+    ret = setuid(0);		/* set real UID = root */
+    if (ret != 0) {
+        fatal("Failed to set uid, %m");
+    }
+    ret = setgid(getegid());
+    if (ret != 0) {
+        fatal("failed to set gid, %m");
+    }
 
 #ifdef BSD
     /* Force the priority back to zero if pppd is running higher. */
-- 
2.39.2