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-rw-r--r--loginutils/add-remove-shell.c12
1 files changed, 10 insertions, 2 deletions
diff --git a/loginutils/add-remove-shell.c b/loginutils/add-remove-shell.c
index 986fe57c5..757e50503 100644
--- a/loginutils/add-remove-shell.c
+++ b/loginutils/add-remove-shell.c
@@ -63,11 +63,19 @@ int add_remove_shell_main(int argc UNUSED_PARAM, char **argv)
orig_fp = fopen_for_read(orig_fn);
new_fn = xasprintf("%s.tmp", orig_fn);
- xmove_fd(xopen(new_fn, O_WRONLY | O_CREAT | O_EXCL), STDOUT_FILENO);
+ /*
+ * O_TRUNC or O_EXCL? At the first glance, O_EXCL looks better,
+ * since it prevents races. But: (1) it requires a retry loop,
+ * (2) if /etc/shells.tmp is *stale*, then retry loop
+ * with O_EXCL will never succeed - it should have a timeout,
+ * after which it should revert to O_TRUNC.
+ * For now, I settle for O_TRUNC instead.
+ */
+ xmove_fd(xopen(new_fn, O_WRONLY | O_CREAT | O_TRUNC), STDOUT_FILENO);
/* TODO:
struct stat sb;
- fstat(fileno(orig_fp), &sb);
+ xfstat(fileno(orig_fp), &sb);
xfchown(STDOUT_FILENO, sb.st_uid, sb.st_gid);
xfchmod(STDOUT_FILENO, sb.st_mode);
*/