SERVER-57267 Fix invalid iterator use in ConnectionPool::dropConnections

(cherry picked from commit 6598a5843ed7318527c8b60bdaaacfe312bd5c51)

1 files changed, 6 insertions, 2 deletions

diff --git a/src/mongo/executor/connection_pool.cpp b/src/mongo/executor/connection_pool.cpp
index 1b4c608a88d..96a8410fd9e 100644
--- a/src/mongo/executor/connection_pool.cpp
+++ b/src/mongo/executor/connection_pool.cpp
@@ -510,8 +510,12 @@ void ConnectionPool::dropConnections(const HostAndPort& hostAndPort) {
 void ConnectionPool::dropConnections(transport::Session::TagMask tags) {
     stdx::lock_guard lk(_mutex);
 
-    for (const auto& pair : _pools) {
-        auto& pool = pair.second;
+    // SpecificPool::triggerShutdown can cause iterator invalidation (e.g. `pool` removing itself
+    // from `_pools`), so we increment `it` early after grabbing a reference to the `pool` it points
+    // to.
+    for (auto it = _pools.begin(); it != _pools.end();) {
+        auto& pool = it->second;
+        ++it;
 
         if (pool->matchesTags(tags))
             continue;