From eb4159ac8857a77040dbcc3113394f487eddafe3 Mon Sep 17 00:00:00 2001
From: Leonid Yuriev <leo@yuriev.ru>
Date: Thu, 12 Sep 2019 00:49:10 +0300
Subject: [PATCH] mdbx-posix: support to close environment after fork() from a
 child process.

Change-Id: I20ab9cf4525bfcacd10043e2afe7e1aa26a2af6c
---
 src/elements/core.c      | 15 ++++++++++++++-
 src/elements/lck-posix.c | 10 ++++++++++
 2 files changed, 24 insertions(+), 1 deletion(-)

diff --git a/src/elements/core.c b/src/elements/core.c
index 52ec3ff9..7765827e 100644
--- a/src/elements/core.c
+++ b/src/elements/core.c
@@ -763,7 +763,9 @@ static int lcklist_detach_locked(MDBX_env *env) {
     mdbx_ensure(env, env->me_lcklist_next == nullptr);
   }
 
-  rc = uniq_check(&env->me_lck_mmap, &inprocess_neighbor);
+  rc = likely(mdbx_getpid() == env->me_pid)
+           ? uniq_check(&env->me_lck_mmap, &inprocess_neighbor)
+           : MDBX_PANIC;
   if (!inprocess_neighbor && env->me_live_reader)
     (void)mdbx_rpid_clear(env);
   if (!MDBX_IS_ERROR(rc))
@@ -3157,6 +3159,17 @@ __cold static int mdbx_env_sync_ex(MDBX_env *env, int force, int nonblock) {
   if (unlikely(env->me_signature != MDBX_ME_SIGNATURE))
     return MDBX_EBADSIGN;
 
+#if MDBX_TXN_CHECKPID || !(defined(_WIN32) || defined(_WIN64))
+  /* Check the PID even if MDBX_TXN_CHECKPID=0 on non-Windows
+   * platforms (i.e. where fork() is available).
+   * This is required to legitimize a call to mdbx_end_close() after fork()
+   * from a child process, that should be allowed to free resources. */
+  if (unlikely(env->me_pid != mdbx_getpid())) {
+    env->me_flags |= MDBX_FATAL_ERROR;
+    return MDBX_PANIC;
+  }
+#endif /* MDBX_TXN_CHECKPID */
+
   unsigned flags = env->me_flags & ~MDBX_NOMETASYNC;
   if (unlikely(flags & (MDBX_RDONLY | MDBX_FATAL_ERROR)))
     return MDBX_EACCESS;
diff --git a/src/elements/lck-posix.c b/src/elements/lck-posix.c
index 792ce75f..b6cd5766 100644
--- a/src/elements/lck-posix.c
+++ b/src/elements/lck-posix.c
@@ -176,6 +176,8 @@ static int lck_op(mdbx_filehandle_t fd, int cmd, int lck, off_t offset,
 MDBX_INTERNAL_FUNC int mdbx_rpid_set(MDBX_env *env) {
   assert(env->me_lfd != INVALID_HANDLE_VALUE);
   assert(env->me_pid > 0);
+  if (unlikely(mdbx_getpid() != env->me_pid))
+    return MDBX_PANIC;
   return lck_op(env->me_lfd, op_setlk, F_WRLCK, env->me_pid, 1);
 }
 
@@ -195,6 +197,8 @@ MDBX_INTERNAL_FUNC int mdbx_rpid_check(MDBX_env *env, mdbx_pid_t pid) {
 
 MDBX_INTERNAL_FUNC int __cold mdbx_lck_seize(MDBX_env *env) {
   assert(env->me_fd != INVALID_HANDLE_VALUE);
+  if (unlikely(mdbx_getpid() != env->me_pid))
+    return MDBX_PANIC;
 #if MDBX_USE_OFDLOCKS
   if (unlikely(op_setlk == 0))
     choice_fcntl();
@@ -283,6 +287,9 @@ MDBX_INTERNAL_FUNC int __cold mdbx_lck_seize(MDBX_env *env) {
 
 MDBX_INTERNAL_FUNC int mdbx_lck_downgrade(MDBX_env *env) {
   assert(env->me_lfd != INVALID_HANDLE_VALUE);
+  if (unlikely(mdbx_getpid() != env->me_pid))
+    return MDBX_PANIC;
+
   int rc = MDBX_SUCCESS;
   if ((env->me_flags & MDBX_EXCLUSIVE) == 0) {
     rc = lck_op(env->me_fd, op_setlk, F_UNLCK, 0, env->me_pid);
@@ -301,6 +308,9 @@ MDBX_INTERNAL_FUNC int mdbx_lck_downgrade(MDBX_env *env) {
 
 MDBX_INTERNAL_FUNC int __cold mdbx_lck_destroy(MDBX_env *env,
                                                MDBX_env *inprocess_neighbor) {
+  if (unlikely(mdbx_getpid() != env->me_pid))
+    return MDBX_PANIC;
+
   int rc = MDBX_SUCCESS;
   if (env->me_lfd != INVALID_HANDLE_VALUE && !inprocess_neighbor &&
       env->me_lck &&