diff -up nfs-utils-2.3.3/support/nfs/conffile.c.orig nfs-utils-2.3.3/support/nfs/conffile.c

--- nfs-utils-2.3.3/support/nfs/conffile.c.orig	2018-09-06 14:09:08.000000000 -0400

+++ nfs-utils-2.3.3/support/nfs/conffile.c	2019-04-25 10:58:27.199907596 -0400

@@ -50,6 +50,7 @@

 #include <err.h>

 #include <syslog.h>

 #include <libgen.h>

+#include <sys/file.h>

 #include "conffile.h"

 #include "xlog.h"

@@ -509,6 +510,17 @@ conf_readfile(const char *path)

 			return NULL;

 		}

+		/* Grab a shared lock to ensure its not mid-rewrite */

+		if (flock(fd, LOCK_SH)) {

+			xlog_warn("conf_readfile: attempt to grab read lock failed: %s",

+				strerror(errno));

+			goto fail;

+		}

+

+		/* only after we have the lock, check the file size ready to read it */

+		sz = lseek(fd, 0, SEEK_END);

+		lseek(fd, 0, SEEK_SET);

+

 		new_conf_addr = malloc(sz+1);

 		if (!new_conf_addr) {

 			xlog_warn("conf_readfile: malloc (%lu) failed", (unsigned long)sz);

@@ -1588,6 +1600,17 @@ flush_outqueue(struct tailhead *queue, F

 	return 0;

 }

+/* append one queue to another */

+static void

+append_queue(struct tailhead *inq, struct tailhead *outq)

+{

+	while (inq->tqh_first != NULL) {

+		struct outbuffer *ob = inq->tqh_first;

+		TAILQ_REMOVE(inq, ob, link);

+		TAILQ_INSERT_TAIL(outq, ob, link);

+	}

+}

+

 /* read one line of text from a file, growing the buffer as necessary */

 static int

 read_line(char **buff, int *buffsize, FILE *in)

@@ -1728,6 +1751,16 @@ is_folded(const char *line)

 	return false;

 }

+static int

+lock_file(FILE *f)

+{

+	int ret;

+	ret = flock(fileno(f), LOCK_EX);

+	if (ret) 

+		xlog(L_ERROR, "Error could not lock the file");

+	return ret;

+}

+

 /***

  * Write a value to an nfs.conf style filename

  *

@@ -1738,15 +1771,14 @@ int

 conf_write(const char *filename, const char *section, const char *arg,

 	   const char *tag, const char *value)

 {

-	int fdout = -1;

-	char *outpath = NULL;

-	FILE *outfile = NULL;

 	FILE *infile = NULL;

 	int ret = 1;

 	struct tailhead outqueue;

+	struct tailhead inqueue;

 	char * buff = NULL;

 	int buffsize = 0;

+	TAILQ_INIT(&inqueue);

 	TAILQ_INIT(&outqueue);

 	if (!filename) {

@@ -1759,26 +1791,7 @@ conf_write(const char *filename, const c

 		return ret;

 	}

-	if (asprintf(&outpath, "%s.XXXXXX", filename) == -1) {

-		xlog(L_ERROR, "conf_write: error composing temp filename");

-		return ret;

-	}

-

-	fdout = mkstemp(outpath);

-	if (fdout < 0) {

-		xlog(L_ERROR, "conf_write: open temp file %s failed: %s",

-			 outpath, strerror(errno));

-		goto cleanup;

-	}

-

-	outfile = fdopen(fdout, "w");

-	if (!outfile) {

-		xlog(L_ERROR, "conf_write: fdopen temp file failed: %s",

-			 strerror(errno));

-		goto cleanup;

-	}

-

-	infile = fopen(filename, "r");

+	infile = fopen(filename, "r+");

 	if (!infile) {

 		if (!value) {

 			xlog_warn("conf_write: config file \"%s\" not found, nothing to do", filename);

@@ -1787,18 +1800,29 @@ conf_write(const char *filename, const c

 		}

 		xlog_warn("conf_write: config file \"%s\" not found, creating.", filename);

-		if (append_line(&outqueue, NULL, make_section(section, arg)))

+		infile = fopen(filename, "wx");

+		if (!infile) {

+			xlog(L_ERROR, "conf_write: Error creating config file \"%s\".", filename);

+			goto cleanup;

+		}

+

+		if (lock_file(infile))

 			goto cleanup;

-		if (append_line(&outqueue, NULL, make_tagline(tag, value)))

+		if (append_line(&inqueue, NULL, make_section(section, arg)))

 			goto cleanup;

-		if (flush_outqueue(&outqueue, outfile))

+		if (append_line(&inqueue, NULL, make_tagline(tag, value)))

 			goto cleanup;

+

+		append_queue(&inqueue, &outqueue);

 	} else {

 		bool found = false;

 		int err = 0;

+		if (lock_file(infile))

+			goto cleanup;

+

 		buffsize = 4096;

 		buff = calloc(1, buffsize);

 		if (buff == NULL) {

@@ -1813,7 +1837,7 @@ conf_write(const char *filename, const c

 			/* read in one section worth of lines */

 			do {

 				if (*buff != '\0') {

-					if (append_line(&outqueue, NULL, strdup(buff)))

+					if (append_line(&inqueue, NULL, strdup(buff)))

 						goto cleanup;

 				}

@@ -1821,7 +1845,7 @@ conf_write(const char *filename, const c

 			} while (err == 0 && buff[0] != '[');

 			/* find the section header */

-			where = TAILQ_FIRST(&outqueue);

+			where = TAILQ_FIRST(&inqueue);

 			while (where != NULL) {

 				if (where->text != NULL && where->text[0] == '[')

 					break;

@@ -1845,7 +1869,7 @@ conf_write(const char *filename, const c

 					/* remove current tag */

 					do {

 						struct outbuffer *next = TAILQ_NEXT(where, link);

-						TAILQ_REMOVE(&outqueue, where, link);

+						TAILQ_REMOVE(&inqueue, where, link);

 						if (is_folded(where->text))

 							again = true;

 						else

@@ -1857,14 +1881,14 @@ conf_write(const char *filename, const c

 					/* insert new tag */

 					if (value) {

-						if (append_line(&outqueue, prev, make_tagline(tag, value)))

+						if (append_line(&inqueue, prev, make_tagline(tag, value)))

 							goto cleanup;

 					}

 				} else

 				/* no existing assignment found and we need to add one */

 				if (value) {

 					/* rewind past blank lines and comments */

-					struct outbuffer *tail = TAILQ_LAST(&outqueue, tailhead);

+					struct outbuffer *tail = TAILQ_LAST(&inqueue, tailhead);

 					/* comments immediately before a section usually relate

 					 * to the section below them */

@@ -1876,7 +1900,7 @@ conf_write(const char *filename, const c

 						tail = TAILQ_PREV(tail, tailhead, link);

 					/* now add the tag here */

-					if (append_line(&outqueue, tail, make_tagline(tag, value)))

+					if (append_line(&inqueue, tail, make_tagline(tag, value)))

 						goto cleanup;

 					found = true;

@@ -1886,49 +1910,45 @@ conf_write(const char *filename, const c

 			/* EOF and correct section not found, so add one */

 			if (err && !found && value) {

 				/* did the last section end in a blank line */

-				struct outbuffer *tail = TAILQ_LAST(&outqueue, tailhead);

+				struct outbuffer *tail = TAILQ_LAST(&inqueue, tailhead);

 				if (tail && !is_empty(tail->text)) {

 					/* no, so add one for clarity */

-					if (append_line(&outqueue, NULL, strdup("\n")))

+					if (append_line(&inqueue, NULL, strdup("\n")))

 						goto cleanup;

 				}

 				/* add the new section header */

-				if (append_line(&outqueue, NULL, make_section(section, arg)))

+				if (append_line(&inqueue, NULL, make_section(section, arg)))

 					goto cleanup;

 				/* now add the tag */

-				if (append_line(&outqueue, NULL, make_tagline(tag, value)))

+				if (append_line(&inqueue, NULL, make_tagline(tag, value)))

 					goto cleanup;

 			}

-			/* we are done with this section, write it out */

-			if (flush_outqueue(&outqueue, outfile))

-				goto cleanup;

+			/* we are done with this section, move it to the out queue */

+			append_queue(&inqueue, &outqueue);

 		} while(err == 0);

 	}

-	if (infile) {

-		fclose(infile);

-		infile = NULL;

-	}

+	/* now rewind and overwrite the file with the updated data */

+	rewind(infile);

-	fdout = -1;

-	if (fclose(outfile)) {

-		xlog(L_ERROR, "Error writing config file: %s", strerror(errno));

+	if (ftruncate(fileno(infile), 0)) {

+		xlog(L_ERROR, "Error truncating config file");

 		goto cleanup;

 	}

-	/* now swap the old file for the new one */

-	if (rename(outpath, filename)) {

-		xlog(L_ERROR, "Error updating config file: %s: %s\n", filename, strerror(errno));

-		ret = 1;

-	} else {

-		ret = 0;

-		free(outpath);

-		outpath = NULL;

+	if (flush_outqueue(&outqueue, infile))

+		goto cleanup;

+

+	if (infile) {

+		fclose(infile);

+		infile = NULL;

 	}

+	ret = 0;

+

 cleanup:

 	flush_outqueue(&outqueue, NULL);

@@ -1936,11 +1956,5 @@ cleanup:

 		free(buff);

 	if (infile)

 		fclose(infile);

-	if (fdout != -1)

-		close(fdout);

-	if (outpath) {

-		unlink(outpath);

-		free(outpath);

-	}

 	return ret;

 }