From 870bd8a117042ffe28818b9669448d2ff0984414 Mon Sep 17 00:00:00 2001 From: Kyotaro Horiguchi Date: Wed, 20 Sep 2023 13:16:35 +0900 Subject: [PATCH v3 2/3] Improve pg_ctl postmaster process check on Windows Currently pg_ctl on Windows does not verify that it actually executed a postmaster process due to lack of process ID knowledge. This can lead to false positives in cases where another pg_ctl instance starts a different server simultaneously. This patch adds the capability to identify the process ID of the launched postmaster on Windows, similar to other OS versions, ensuring more reliable detection of concurrent server startups. --- src/bin/pg_ctl/pg_ctl.c | 107 +++++++++++++++++++++++++++++++++++++--- 1 file changed, 99 insertions(+), 8 deletions(-) diff --git a/src/bin/pg_ctl/pg_ctl.c b/src/bin/pg_ctl/pg_ctl.c index 3ac2fcc004..2563f15376 100644 --- a/src/bin/pg_ctl/pg_ctl.c +++ b/src/bin/pg_ctl/pg_ctl.c @@ -132,6 +132,7 @@ static void adjust_data_dir(void); #ifdef WIN32 #include +#include static bool pgwin32_IsInstalled(SC_HANDLE); static char *pgwin32_CommandLine(bool); static void pgwin32_doRegister(void); @@ -142,6 +143,7 @@ static void WINAPI pgwin32_ServiceMain(DWORD, LPTSTR *); static void pgwin32_doRunAsService(void); static int CreateRestrictedProcess(char *cmd, PROCESS_INFORMATION *processInfo, bool as_service); static PTOKEN_PRIVILEGES GetPrivilegesToDelete(HANDLE hToken); +static pid_t pgwin32_find_postmaster_pid(pid_t shell_pid, bool *is_valid); #endif static pid_t get_pgpid(bool is_status_request); @@ -609,7 +611,20 @@ wait_for_postmaster_start(pid_t pm_pid, bool do_checkpoint) /* File is complete enough for us, parse it */ pid_t pmpid; time_t pmstart; +#ifndef WIN32 + pid_t wait_pid = pm_pid; +#else + bool is_valid; + + pid_t wait_pid = pgwin32_find_postmaster_pid(pm_pid, &is_valid); + /* Quick exit if something is wrong */ + if (!is_valid) + { + free_readfile(optlines); + return POSTMASTER_FAILED; + } +#endif /* * Make sanity checks. If it's for the wrong PID, or the recorded * start time is before pg_ctl started, then either we are looking @@ -619,14 +634,8 @@ wait_for_postmaster_start(pid_t pm_pid, bool do_checkpoint) */ pmpid = atol(optlines[LOCK_FILE_LINE_PID - 1]); pmstart = atol(optlines[LOCK_FILE_LINE_START_TIME - 1]); - if (pmstart >= start_time - 2 && -#ifndef WIN32 - pmpid == pm_pid -#else - /* Windows can only reject standalone-backend PIDs */ - pmpid > 0 -#endif - ) + + if (pmstart >= start_time - 2 && pmpid == wait_pid) { /* * OK, seems to be a valid pidfile from our child. Check the @@ -1950,6 +1959,88 @@ GetPrivilegesToDelete(HANDLE hToken) return tokenPrivs; } + +/* + * Find the PID of the launched postmaster. + * + * On Windows, the cmd.exe doesn't support the exec command. As a result, we + * don't directly get the postmaster's PID. This function identifies the PID of + * the postmaster started by the child cmd.exe. + * + * Returns the postmaster's PID. If the shell is alive but the postmaster is + * missing, returns 0. If the shell executes several processes or the process + * is dead, is_valid flag is set to false. + * + * This function uses PID 0 as an invalid value, assuming the system idle + * process occupies it and it won't be a PID for a shell or postmaster. + */ +pid_t +pgwin32_find_postmaster_pid(pid_t shell_pid, bool *is_valid) +{ + HANDLE hSnapshot; + PROCESSENTRY32 ppe; + pid_t pm_pid = 0; /* abusing 0 as an invalid value */ + bool shell_exists = false; + DWORD last_error; + *is_valid = true; + + /* create a process snapshot */ + hSnapshot = CreateToolhelp32Snapshot(TH32CS_SNAPPROCESS, 0); + if (hSnapshot == INVALID_HANDLE_VALUE) + { + write_stderr(_("%s: could not create a snapshot: error code %lu\n"), + progname, (unsigned long) GetLastError()); + exit(1); + } + + /* start iterating on the snapshot */ + ppe.dwSize = sizeof(PROCESSENTRY32); + if (!Process32First(hSnapshot, &ppe)) + { + write_stderr(_("%s: cound not retrieve information about the process: error code %lu\n"), + progname, GetLastError()); + exit(1); + } + + /* + * Iterate over the snapshot. + * + * Check for shell existence and duplicate processes for reliability. + * + * The launcher shell may start other instances of cmd.exe or programs + * besides postgres.exe. It's important to verify the program file name. + */ + do + { + if (ppe.th32ProcessID == shell_pid) + shell_exists = true; + else if (ppe.th32ParentProcessID == shell_pid && + strcmp("postgres.exe", ppe.szExeFile) == 0) + { + /* assuming the launching shell executes a single process */ + if (pm_pid != ppe.th32ProcessID && pm_pid != 0) + *is_valid = false; + pm_pid = ppe.th32ProcessID; + } + } + while (Process32Next(hSnapshot, &ppe)); + + /* avoid multiple calls primary for clarity, not out of necessity */ + last_error = GetLastError(); + if (last_error != ERROR_NO_MORE_FILES) + { + write_stderr(_("%s: cound not retrieve information about the process: error code %lu\n"), + progname, last_error); + exit(1); + } + CloseHandle(hSnapshot); + + /* check if the process is still alive */ + if (!shell_exists) + *is_valid = false; + + return pm_pid; +} #endif /* WIN32 */ static void -- 2.27.0