From 00e1f2b8a86349acbaf14e654e4874525970cd01 Mon Sep 17 00:00:00 2001 From: Volker Klasen Date: Fri, 14 Jan 2022 09:31:55 +0100 Subject: [PATCH] MDEV-26212: auth_pam: Replaced fork() + exec() by posix_spawn() to avoid ENOMEM when server process uses more memory than is still free and memory overcommit is disabled --- plugin/auth_pam/auth_pam.c | 71 ++++++++++++++++++-------------------- 1 file changed, 34 insertions(+), 37 deletions(-) diff --git a/plugin/auth_pam/auth_pam.c b/plugin/auth_pam/auth_pam.c index 35272c6b7cd..29d65d7bc07 100644 --- a/plugin/auth_pam/auth_pam.c +++ b/plugin/auth_pam/auth_pam.c @@ -23,6 +23,7 @@ #include #include "auth_pam_tool.h" #include +#include #ifndef DBUG_OFF static char pam_debug = 0; @@ -43,6 +44,8 @@ static const int tool_name_len= 31; */ static const unsigned int sleep_limit= 5; +extern char **environ; + static int pam_auth(MYSQL_PLUGIN_VIO *vio, MYSQL_SERVER_AUTH_INFO *info) { int p_to_c[2], c_to_p[2]; /* Parent-to-child and child-to-parent pipes. */ @@ -51,6 +54,7 @@ static int pam_auth(MYSQL_PLUGIN_VIO *vio, MYSQL_SERVER_AUTH_INFO *info) unsigned char field, *pkt; unsigned int n_sleep= 0; useconds_t sleep_time= 100; + posix_spawn_file_actions_t child_fd_actions; PAM_DEBUG((stderr, "PAM: opening pipes.\n")); if (pipe(p_to_c) < 0 || pipe(c_to_p) < 0) @@ -58,54 +62,47 @@ static int pam_auth(MYSQL_PLUGIN_VIO *vio, MYSQL_SERVER_AUTH_INFO *info) /* Error creating pipes. */ return CR_ERROR; } - PAM_DEBUG((stderr, "PAM: forking.\n")); - if ((proc_id= fork()) < 0) + + PAM_DEBUG((stderr, "PAM: setting up file actions.\n")); + if (posix_spawn_file_actions_init(&child_fd_actions) || + posix_spawn_file_actions_addclose(&child_fd_actions, p_to_c[1]) || + posix_spawn_file_actions_addclose(&child_fd_actions, c_to_p[0]) || + posix_spawn_file_actions_adddup2(&child_fd_actions, p_to_c[0], 0) || + posix_spawn_file_actions_adddup2(&child_fd_actions, c_to_p[1], 1)) { - /* Error forking. */ + /* Error setting up file actions. */ close(p_to_c[0]); close(c_to_p[1]); goto error_ret; } - if (proc_id == 0) + char toolpath[FN_REFLEN]; + size_t plugin_dir_len= strlen(opt_plugin_dir); + PAM_DEBUG((stderr, "PAM: check tool directory: %s, %s.\n", + opt_plugin_dir, tool_name)); + if (plugin_dir_len + tool_name_len + 2 > sizeof(toolpath)) { - /* The 'sandbox' process started. */ - char toolpath[FN_REFLEN]; - size_t plugin_dir_len= strlen(opt_plugin_dir); - - PAM_DEBUG((stderr, "PAM: Child process prepares pipes.\n")); - - if (close(p_to_c[1]) < 0 || - close(c_to_p[0]) < 0 || - dup2(p_to_c[0], 0) < 0 || /* Parent's pipe to STDIN. */ - dup2(c_to_p[1], 1) < 0) /* Sandbox's pipe to STDOUT. */ - { - exit(-1); - } + /* Tool path too long. */ + close(p_to_c[0]); + close(c_to_p[1]); + goto error_ret; + } - PAM_DEBUG((stderr, "PAM: check tool directory: %s, %s.\n", - opt_plugin_dir, tool_name)); - if (plugin_dir_len + tool_name_len + 2 > sizeof(toolpath)) - { - /* Tool path too long. */ - exit(-1); - } + memcpy(toolpath, opt_plugin_dir, plugin_dir_len); + if (plugin_dir_len && toolpath[plugin_dir_len-1] != FN_LIBCHAR) + toolpath[plugin_dir_len++]= FN_LIBCHAR; + memcpy(toolpath+plugin_dir_len, tool_name, tool_name_len+1); + char *const argv[2]= {toolpath, NULL}; - memcpy(toolpath, opt_plugin_dir, plugin_dir_len); - if (plugin_dir_len && toolpath[plugin_dir_len-1] != FN_LIBCHAR) - toolpath[plugin_dir_len++]= FN_LIBCHAR; - memcpy(toolpath+plugin_dir_len, tool_name, tool_name_len+1); - - PAM_DEBUG((stderr, "PAM: execute pam sandbox [%s].\n", toolpath)); - (void) execl(toolpath, toolpath, NULL); - PAM_DEBUG((stderr, "PAM: exec() failed.\n")); - my_printf_error(1, "PAM: Cannot execute %s (errno: %M)", ME_ERROR_LOG_ONLY, - toolpath, errno); - exit(-1); + PAM_DEBUG((stderr, "PAM: spawn pam sandbox [%s].\n", toolpath)); + if (posix_spawn(&proc_id, toolpath, &child_fd_actions, NULL, argv, environ)) + { + /* Error spawning process. */ + close(p_to_c[0]); + close(c_to_p[1]); + goto error_ret; } - /* Parent process continues. */ - PAM_DEBUG((stderr, "PAM: parent continues.\n")); if (close(p_to_c[0]) < 0 || close(c_to_p[1]) < 0) -- 2.34.1