If (flags & O_TRUNC), don't truncate the file until we've successfully

locked it.

MFC after:	3 weeks

1 files changed, 11 insertions, 1 deletions

diff --git a/lib/libutil/flopen.c b/lib/libutil/flopen.c
index 687ebac..92254cc 100644
--- a/lib/libutil/flopen.c
+++ b/lib/libutil/flopen.c
@@ -41,7 +41,7 @@ __FBSDID("$FreeBSD$");
 int
 flopen(const char *path, int flags, ...)
 {
-	int fd, operation, serrno;
+	int fd, operation, serrno, truncate;
 	struct stat sb, fsb;
 	mode_t mode;
 
@@ -62,6 +62,9 @@ flopen(const char *path, int flags, ...)
 	if (flags & O_NONBLOCK)
 		operation |= LOCK_NB;
 
+	truncate = (flags & O_TRUNC);
+	flags |= ~O_TRUNC;
+
 	for (;;) {
 		if ((fd = open(path, flags, mode)) == -1)
 			/* non-existent or no access */
@@ -91,6 +94,13 @@ flopen(const char *path, int flags, ...)
 			close(fd);
 			continue;
 		}
+		if (truncate && ftruncate(fd, 0) != 0) {
+			/* can't happen [tm] */
+			serrno = errno;
+			close(fd);
+			errno = serrno;
+			return (-1);
+		}
 		return (fd);
 	}
 }