From 8ff0f36e00626451e92511f59dd35e3ba836806f Mon Sep 17 00:00:00 2001
From: Yu Watanabe <watanabe.yu+github@gmail.com>
Date: Thu, 28 Sep 2023 10:46:23 +0900
Subject: [PATCH] mmap-cache: check if mmap protection mode is consistent when
 fd is already managed

Otherwise, MMapFileDescriptor with an unexpected protection mode may be
returned.
---
 src/libsystemd/sd-journal/mmap-cache.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/src/libsystemd/sd-journal/mmap-cache.c b/src/libsystemd/sd-journal/mmap-cache.c
index 6c2c26fde80..992bf1c4fc5 100644
--- a/src/libsystemd/sd-journal/mmap-cache.c
+++ b/src/libsystemd/sd-journal/mmap-cache.c
@@ -551,6 +551,8 @@ int mmap_cache_add_fd(MMapCache *m, int fd, int prot, MMapFileDescriptor **ret)
 
         existing = hashmap_get(m->fds, FD_TO_PTR(fd));
         if (existing) {
+                if (existing->prot != prot)
+                        return -EEXIST;
                 if (ret)
                         *ret = existing;
                 return 0;
-- 
2.47.3