Set and restore umask to ensure lockfiles are atomically created with mode 0664.

Using the default 0022 yields lock files with g-w, so trying to flock(2)
from a different user failed.

1 files changed, 8 insertions, 3 deletions

diff --git a/webmap-download b/webmap-download
index 087e7fc..fcbbd16 100755
--- a/webmap-download
+++ b/webmap-download
@@ -310,10 +310,15 @@ def main() -> NoReturn:
             # place an exclusive lock on a lockfile as the destination can be used by other layers
             # hence might be updated in parallel
             if lockdir_fd is not None:
+                umask = os.umask(0o002)
                 lockfile = getSourcePathLockFileName(dest)
-                # use O_TRUNC to bump lockfile's mtime
-                lock_fd = os.open(lockfile, O_WRONLY|O_CREAT|O_TRUNC|O_CLOEXEC, mode=0o664,
-                                  dir_fd=lockdir_fd)
+                try:
+                    # use O_TRUNC to bump lockfile's mtime
+                    lock_fd = os.open(lockfile, O_WRONLY|O_CREAT|O_TRUNC|O_CLOEXEC, mode=0o664,
+                                      dir_fd=lockdir_fd)
+                finally:
+                    os.umask(umask)
+
             try:
                 if lockdir_fd is not None:
                     logging.debug('flock("%s", LOCK_EX)', lockfile)