From: Theodore Ts'o <tytso@mit.edu>
Date: Sat, 19 Sep 2015 01:37:53 +0000 (-0400)
Subject: subst: work around an NFS bug
X-Git-Tag: v1.43-WIP-2016-03-15~52
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=e5a82003d1b3b7ea01f60dadb49c3bbc60e4ebb7;p=thirdparty%2Fe2fsprogs.git

subst: work around an NFS bug

When running on NFS, opening files with 0444 perms for writing can
sometimes fail.  This is arguably an NFS server bug, but work around
it by creating the file with 0644 permissions, and only change the
permissions to be 0444 right before we close the file.

URL: https://bugs.gentoo.org/550986
Reported-by: Mike Frysinger <vapier@gentoo.org>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
---

diff --git a/util/subst.c b/util/subst.c
index f36adb4d8..70dc0bc12 100644
--- a/util/subst.c
+++ b/util/subst.c
@@ -319,7 +319,7 @@ int main(int argc, char **argv)
 {
 	char	line[2048];
 	int	c;
-	int	fd;
+	int	fd, ofd = -1;
 	FILE	*in, *out, *old = NULL;
 	char	*outfn = NULL, *newfn = NULL;
 	int	verbose = 0;
@@ -370,12 +370,12 @@ int main(int argc, char **argv)
 		}
 		strcpy(newfn, outfn);
 		strcat(newfn, ".new");
-		fd = open(newfn, O_CREAT|O_TRUNC|O_RDWR, 0444);
-		if (fd < 0) {
+		ofd = open(newfn, O_CREAT|O_TRUNC|O_RDWR, 0644);
+		if (ofd < 0) {
 			perror(newfn);
 			exit(1);
 		}
-		out = fdopen(fd, "w+");
+		out = fdopen(ofd, "w+");
 		if (!out) {
 			perror("fdopen");
 			exit(1);
@@ -429,12 +429,16 @@ int main(int argc, char **argv)
 					printf("Using original atime\n");
 				set_utimes(outfn, fileno(old), tv);
 			}
+			if (ofd >= 0)
+				(void) fchmod(ofd, 0444);
 			fclose(out);
 			if (unlink(newfn) < 0)
 				perror("unlink");
 		} else {
 			if (verbose)
 				printf("Creating or replacing %s.\n", outfn);
+			if (ofd >= 0)
+				(void) fchmod(ofd, 0444);
 			fclose(out);
 			if (old)
 				fclose(old);