Fix acpidump CID 1011278 (Buffer not null terminated) and other issues.

Coverity reports that a buffer used for temporary file generation
might not be NUL terminated by strncpy().  This is probably not
true because the input gets passed through realpath(), but if the
path name is sufficiently long the name could be truncated and cause
other problems.  The code for generating the temp file names is
also overly complex. Instead of a bunch of calls to strncpy() and
and strncat(), simplify by using snprintf() and add checks for for
unexpected truncation.

Also, the output file created by iasl -d is predictable, so use
mkdtemp() to create a directory to hold the iasl input and output
files.

Check the return values of more syscalls.

Index: acpidump/acpi.c
===================================================================
--- acpidump/acpi.c	(revision 300099)
+++ acpidump/acpi.c	(working copy)
@@ -1466,27 +1466,34 @@
 void
 aml_disassemble(ACPI_TABLE_HEADER *rsdt, ACPI_TABLE_HEADER *dsdp)
 {
-	char buf[PATH_MAX], tmpstr[PATH_MAX];
+	char buf[PATH_MAX], tmpstr[PATH_MAX], wrkdir[PATH_MAX];
+	const char *iname = "/acpdump.din";
+	const char *oname = "/acpdump.dsl";
 	const char *tmpdir;
-	char *tmpext;
 	FILE *fp;
 	size_t len;
-	int fd;
+	int fd, status;
+	pid_t pid;
 
 	tmpdir = getenv("TMPDIR");
 	if (tmpdir == NULL)
 		tmpdir = _PATH_TMP;
-	strncpy(tmpstr, tmpdir, sizeof(tmpstr));
-	if (realpath(tmpstr, buf) == NULL) {
+	if (realpath(tmpdir, buf) == NULL) {
 		perror("realpath tmp dir");
 		return;
 	}
-	strncpy(tmpstr, buf, sizeof(tmpstr));
-	strncat(tmpstr, "/acpidump.", sizeof(tmpstr) - strlen(buf));
-	len = strlen(tmpstr);
-	tmpext = tmpstr + len;
-	strncpy(tmpext, "XXXXXX", sizeof(tmpstr) - len);
-	fd = mkstemp(tmpstr);
+	len = sizeof(wrkdir) - strlen(iname);
+	if ((size_t)snprintf(wrkdir, len, "%s/acpidump.XXXXXX", buf) > len-1 ) {
+		fprintf(stderr, "$TMPDIR too long\n");
+		return;
+	}
+	if  (mkdtemp(wrkdir) == NULL) {
+		perror("mkdtemp tmp working dir");
+		return;
+	}
+	assert((size_t)snprintf(tmpstr, sizeof(tmpstr), "%s%s", wrkdir, iname)
+		<= sizeof(tmpstr) - 1);
+	fd = open(tmpstr, O_CREAT | O_WRONLY, S_IRUSR | S_IWUSR);
 	if (fd < 0) {
 		perror("iasl tmp file");
 		return;
@@ -1495,7 +1502,7 @@
 	close(fd);
 
 	/* Run iasl -d on the temp file */
-	if (fork() == 0) {
+	if ((pid = fork()) == 0) {
 		close(STDOUT_FILENO);
 		if (vflag == 0)
 			close(STDERR_FILENO);
@@ -1502,21 +1509,39 @@
 		execl("/usr/sbin/iasl", "iasl", "-d", tmpstr, NULL);
 		err(1, "exec");
 	}
+	if (pid > 0)
+		wait(&status);
+	if (unlink(tmpstr) < 0) {
+		perror("unlink");
+		goto out;
+	}
+	if (pid < 0) {
+		perror("fork");
+		goto out;
+	}
+	if (status != 0) {
+		fprintf(stderr, "iast exit status = %d\n", status);
+	}
 
-	wait(NULL);
-	unlink(tmpstr);
-
 	/* Dump iasl's output to stdout */
-	strncpy(tmpext, "dsl", sizeof(tmpstr) - len);
+	assert((size_t)snprintf(tmpstr, sizeof(tmpstr), "%s%s", wrkdir, oname)
+		<= sizeof(tmpstr) -1);
 	fp = fopen(tmpstr, "r");
-	unlink(tmpstr);
+	if (unlink(tmpstr) < 0) {
+		perror("unlink");
+		goto out;
+	}
 	if (fp == NULL) {
 		perror("iasl tmp file (read)");
-		return;
+		goto out;
 	}
 	while ((len = fread(buf, 1, sizeof(buf), fp)) > 0)
 		fwrite(buf, 1, len, stdout);
 	fclose(fp);
+
+    out:
+	if (rmdir(wrkdir) < 0)
+		perror("rmdir");
 }
 
 void