From ba5d26d85d0c4250b10a46a5c9cd3a3e1f0ce43b Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Christian=20G=C3=B6ttsche?= <cgzones@googlemail.com>
Date: Fri, 4 Nov 2022 19:36:31 +0100
Subject: [PATCH] loop-util: open lock fd read-only

flock(2) works with file descriptors opened with O_RDONLY.

This affects SELinux systems where access to block devices is quite
restricted to avoid bypasses on filesystem objects.

(cherry picked from commit 3e6b7d2626de9c0faf8b34b2629e8d6d8fa85a7d)

Related #2138081
---
 src/shared/loop-util.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/shared/loop-util.c b/src/shared/loop-util.c
index 731ce29112..fb7e80b1b5 100644
--- a/src/shared/loop-util.c
+++ b/src/shared/loop-util.c
@@ -77,7 +77,7 @@ static int open_lock_fd(int primary_fd, int operation) {
         assert(primary_fd >= 0);
         assert(IN_SET(operation & ~LOCK_NB, LOCK_SH, LOCK_EX));
 
-        lock_fd = fd_reopen(primary_fd, O_RDWR|O_CLOEXEC|O_NONBLOCK|O_NOCTTY);
+        lock_fd = fd_reopen(primary_fd, O_RDONLY|O_CLOEXEC|O_NONBLOCK|O_NOCTTY);
         if (lock_fd < 0)
                 return lock_fd;