Use stpeprintf() where appropriate

This function allows reducing error checking (since errors are
propagated across chained calls), and also simplifies the calculation of
the start and end of the buffer where the string should be written.

Moreover, the new code is more optimized, since many calls to strlen(3)
have been removed.

Signed-off-by: Alejandro Colomar <alx@kernel.org>

libmisc/idmapping.c

@@ -12,6 +12,7 @@
 #include <stdlib.h>
 #include <stdio.h>
 #include "prototypes.h"
+#include "stpeprintf.h"
 #include "idmapping.h"
 #if HAVE_SYS_CAPABILITY_H
 #include <sys/prctl.h>
@@ -141,7 +142,7 @@ void write_mapping(int proc_dir_fd, int ranges, const struct map_range *mappings
 	int idx;
 	const struct map_range *mapping;
 	size_t bufsize;
-	char *buf, *pos;
+	char *buf, *pos, *end;
 	int fd;
 
 #if HAVE_SYS_CAPABILITY_H
@@ -189,21 +190,20 @@ void write_mapping(int proc_dir_fd, int ranges, const struct map_range *mappings
 
 	bufsize = ranges * ((ULONG_DIGITS + 1) * 3);
 	pos = buf = xmalloc(bufsize);
+	end = buf + bufsize;
 
 	/* Build the mapping command */
 	mapping = mappings;
 	for (idx = 0; idx < ranges; idx++, mapping++) {
 		/* Append this range to the string that will be written */
-		int written = snprintf(pos, bufsize - (pos - buf),
+		pos = stpeprintf(pos, end, "%lu %lu %lu\n",
-			"%lu %lu %lu\n",
+		                 mapping->upper,
-			mapping->upper,
+		                 mapping->lower,
-			mapping->lower,
+		                 mapping->count);
-			mapping->count);
+	}
-		if ((written <= 0) || ((size_t)written >= (bufsize - (pos - buf)))) {
+	if (pos == end || pos == NULL) {
-			fprintf(log_get_logfd(), _("%s: snprintf failed!\n"), log_get_progname());
+		fprintf(log_get_logfd(), _("%s: stpeprintf failed!\n"), log_get_progname());
-			exit(EXIT_FAILURE);
+		exit(EXIT_FAILURE);
-		}
-		pos += written;
 	}
 
 	/* Write the mapping to the mapping file */

src/groupmod.c

@@ -35,6 +35,7 @@
 #include "sgroupio.h"
 #endif
 #include "shadowlog.h"
+#include "stpeprintf.h"
 /*
  * exit status values
  */
@@ -543,46 +544,49 @@ static void close_files (void)
  */
 static void prepare_failure_reports (void)
 {
+	char *gr, *gr_end;
+#ifdef	SHADOWGRP
+	char *sgr, *sgr_end;
+#endif
+	char *pw, *pw_end;
+
 	info_group.name   = group_name;
 #ifdef	SHADOWGRP
 	info_gshadow.name = group_name;
 #endif
 	info_passwd.name  = group_name;
 
-	info_group.audit_msg   = xmalloc (512);
+	gr                     = xmalloc (512);
+	info_group.audit_msg   = gr;
+	gr_end                 = gr + 512;
 #ifdef	SHADOWGRP
-	info_gshadow.audit_msg = xmalloc (512);
+	sgr                    = xmalloc (512);
+	info_gshadow.audit_msg = sgr;
+	sgr_end                = sgr + 512;
 #endif
-	info_passwd.audit_msg  = xmalloc (512);
+	pw                     = xmalloc (512);
+	info_passwd.audit_msg  = pw;
+	pw_end                 = pw + 512;
 
-	(void) snprintf (info_group.audit_msg, 512,
+	gr = stpeprintf(gr, gr_end, "changing %s; ", gr_dbname ());
-	                 "changing %s; ", gr_dbname ());
 #ifdef	SHADOWGRP
-	(void) snprintf (info_gshadow.audit_msg, 512,
+	sgr = stpeprintf(sgr, sgr_end, "changing %s; ", sgr_dbname ());
-	                 "changing %s; ", sgr_dbname ());
 #endif
-	(void) snprintf (info_passwd.audit_msg, 512,
+	pw = stpeprintf(pw, pw_end, "changing %s; ", pw_dbname ());
-	                 "changing %s; ", pw_dbname ());
 
-	info_group.action   =   info_group.audit_msg
+	info_group.action   = gr;
-	                      + strlen (info_group.audit_msg);
 #ifdef	SHADOWGRP
-	info_gshadow.action =   info_gshadow.audit_msg
+	info_gshadow.action = sgr;
-	                      + strlen (info_gshadow.audit_msg);
 #endif
-	info_passwd.action  =   info_passwd.audit_msg
+	info_passwd.action  = pw;
-	                      + strlen (info_passwd.audit_msg);
 
-	(void) snprintf (info_group.action,
+	gr  = stpeprintf(gr, gr_end,
-	                 512 - strlen (info_group.audit_msg),
 	                 "group %s/%ju", group_name, (uintmax_t) group_id);
 #ifdef	SHADOWGRP
-	(void) snprintf (info_gshadow.action,
+	sgr = stpeprintf(sgr, sgr_end,
-	                 512 - strlen (info_gshadow.audit_msg),
 	                 "group %s", group_name);
 #endif
-	(void) snprintf (info_passwd.action,
+	pw  = stpeprintf(pw, pw_end,
-	                 512 - strlen (info_passwd.audit_msg),
 	                 "group %s/%ju", group_name, (uintmax_t) group_id);
 
 	if (nflg) {
@@ -615,15 +619,13 @@ static void prepare_failure_reports (void)
 	if (gflg) {
 		strncat (info_group.action, ", new gid: ",
 		         511 - strlen (info_group.audit_msg));
-		(void) snprintf (info_group.action+strlen (info_group.action),
+		stpeprintf(info_group.action+strlen (info_group.action),
-		                 512 - strlen (info_group.audit_msg),
+		                 gr_end, "%ju", (uintmax_t) group_newid);
-		                 "%ju", (uintmax_t) group_newid);
 
 		strncat (info_passwd.action, ", new gid: ",
 		         511 - strlen (info_passwd.audit_msg));
-		(void) snprintf (info_passwd.action+strlen (info_passwd.action),
+		stpeprintf(info_passwd.action+strlen (info_passwd.action),
-		                 512 - strlen (info_passwd.audit_msg),
+		                 pw_end, "%ju", (uintmax_t) group_newid);
-		                 "%ju", (uintmax_t) group_newid);
 	}
 	info_group.audit_msg[511]   = '\0';
 #ifdef	SHADOWGRP