From 093331425d1737ea4c3345d46f599be485e55860 Mon Sep 17 00:00:00 2001
From: Aliaksei Makarau <aliaksei.makarau@ibm.com>
Date: Mon, 20 Jun 2022 10:25:54 +0200
Subject: [PATCH] fsmap: switch to using iterator based loop

Segfault was triggered by the fs/mirror test.
The problem is in potential undefined behaviour
after erasing element and iterator invalidation in
FSMap::filter().
Fixed by explicit iterator increment.

Fixes: https://tracker.ceph.com/issues/55134

Signed-off-by: Aliaksei Makarau <aliaksei.makarau@ibm.com>
---
 src/mds/FSMap.h | 34 ++++++++++++++++++++++------------
 1 file changed, 22 insertions(+), 12 deletions(-)

diff --git a/src/mds/FSMap.h b/src/mds/FSMap.h
index 099c1337ceb..5bf2f6b267f 100644
--- a/src/mds/FSMap.h
+++ b/src/mds/FSMap.h
@@ -34,6 +34,22 @@
 #include "common/Formatter.h"
 #include "mds/mdstypes.h"
 
+#if __cplusplus <= 201703L
+template<class Key, class T, class Compare, class Alloc, class Pred>
+typename std::map<Key, T, Compare, Alloc>::size_type
+erase_if(std::map<Key, T, Compare, Alloc>& c, Pred pred) {
+  auto old_size = c.size();
+  for (auto i = c.begin(), last = c.end(); i != last; ) {
+    if (pred(*i)) {
+      i = c.erase(i);
+    } else {
+      ++i;
+    }
+  }
+  return old_size - c.size();
+}
+#endif
+
 class health_check_map_t;
 
 struct ClusterInfo {
@@ -259,19 +275,13 @@ public:
       return;
     }
 
-    for (auto &f : filesystems) {
-      std::string_view fs_name = f.second->mds_map.get_fs_name();
-      if (std::find(allowed.begin(), allowed.end(), fs_name) == allowed.end()) {
-	filesystems.erase(f.first);
-      }
-    }
+    erase_if(filesystems, [&](const auto& f) {
+      return std::find(allowed.begin(), allowed.end(), f.second->mds_map.get_fs_name()) == allowed.end();
+    });
 
-    for (auto r : mds_roles) {
-      std::string_view fs_name = fs_name_from_gid(r.first);
-      if (std::find(allowed.begin(), allowed.end(), fs_name) == allowed.end()) {
-	mds_roles.erase(r.first);
-      }
-    }
+    erase_if(mds_roles, [&](const auto& r) {
+      return std::find(allowed.begin(), allowed.end(), fs_name_from_gid(r.first)) == allowed.end();
+    });
   }
 
   void set_enable_multiple(const bool v)
-- 
2.47.3