diff --git a/ChangeLog b/ChangeLog index b42a4d7..baba19e 100644 --- a/ChangeLog +++ b/ChangeLog @@ -1,3 +1,10 @@ + * Make it possible to use --enable-timeout-stat as well as + --enable-timeout-stat=static for a static background process which + does the final stat system calls + * Do not mix HAVE_TIMEOUT_STAT with WITH_TIMEOUT_STAT + * Add timeout.c/timeout.h for static background process which is able + to read the file name from pipe, does the stat(2) system call, and + writes the result back to a pipe. * Really add ASCII null at command string in add_proc() of pstree.c Changes in 22.16 diff --git a/configure.ac b/configure.ac index 0615f5f..9265d82 100644 --- a/configure.ac +++ b/configure.ac @@ -30,12 +30,16 @@ AC_SUBST([SELINUX_LIB]) # Call fork before all stat calls to stop hanging on NFS mounts AC_SUBST([WITH_TIMEOUT_STAT]) AC_ARG_ENABLE([timeout_stat], - [AS_HELP_STRING([--enable-timeout-stat], [Use a timeout on stat calls])], + [AS_HELP_STRING([--enable-timeout-stat], [Use a timeout on stat calls (optional with argument "static" for a static background process)])], [enable_timeout_stat=$enableval], [enable_timeout_stat="no"]) if test "$enable_timeout_stat" = "yes"; then AC_DEFINE([WITH_TIMEOUT_STAT], [1], [Use timeout on stat calls]) fi +if test "$enable_timeout_stat" = "static"; then + AC_DEFINE([WITH_TIMEOUT_STAT], [2], [Use timeout on stat calls]) +fi +AM_CONDITIONAL([WANT_TIMEOUT_STAT], [test "$enable_timeout_stat" = "static"]) # Enable hardened compile and link flags AC_ARG_ENABLE([harden_flags], diff --git a/src/Makefile.am b/src/Makefile.am index d511f24..a28af7d 100644 --- a/src/Makefile.am +++ b/src/Makefile.am @@ -24,6 +24,9 @@ if WANT_PEEKFD_MIPS endif fuser_SOURCES = fuser.c comm.h signals.c signals.h i18n.h fuser.h lists.h +if WANT_TIMEOUT_STAT + fuser_SOURCES += timeout.c timeout.h +endif fuser_LDADD = @LIBINTL@ diff --git a/src/fuser.c b/src/fuser.c index e4081eb..09548ff 100644 --- a/src/fuser.c +++ b/src/fuser.c @@ -111,9 +111,13 @@ static dev_t device(const char *path); #endif static char *expandpath(const char *path); -typedef int (*stat_t)(const char*, struct stat*); #ifdef WITH_TIMEOUT_STAT +# if (WITH_TIMEOUT_STAT == 2) +# include "timeout.h" +# else +typedef int (*stat_t)(const char*, struct stat*); static int timeout(stat_t func, const char *path, struct stat *buf, unsigned int seconds); +# endif #else #define timeout(func,path,buf,dummy) (func)((path),(buf)) #endif /* WITH_TIMEOUT_STAT */ @@ -1783,7 +1787,7 @@ scan_swaps(struct names *names_head, struct inode_list *ino_head, * Execute stat(2) system call with timeout to avoid deadlock * on network based file systems. */ -#ifdef HAVE_TIMEOUT_STAT +#if defined(WITH_TIMEOUT_STAT) && (WITH_TIMEOUT_STAT == 1) static sigjmp_buf jenv; diff --git a/src/timeout.c b/src/timeout.c new file mode 100644 index 0000000..1fe0354 --- /dev/null +++ b/src/timeout.c @@ -0,0 +1,267 @@ +/* + * timout.c Advanced timeout handling for file system calls + * to avoid deadlocks on remote file shares. + * + * Version: 0.1 07-Sep-2011 Fink + * + * Copyright 2011 Werner Fink, 2011 SUSE LINUX Products GmbH, Germany. + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; either version 2 of the License, or + * (at your option) any later version. + * + * Author: Werner Fink , 2011 + */ + +#ifndef _GNU_SOURCE +# define _GNU_SOURCE +#endif + +#ifndef USE_SOCKETPAIR +# define USE_SOCKETPAIR 1 +#endif + +#ifdef _FEATURES_H +# error Include local config.h before any system header file +#endif +#include "config.h" /* For _FILE_OFFSET_BITS */ + +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include + +#include +#if USE_SOCKETPAIR +# include +# include +# include +# ifndef SHUT_RD +# define SHUT_RD 0 +# endif +# ifndef SHUT_WR +# define SHUT_WR 1 +# endif +# undef pipe +# define pipe(v) (((socketpair(AF_UNIX,SOCK_STREAM,0,v) < 0) || \ + (shutdown((v)[1],SHUT_RD) < 0) || (shutdown((v)[0],SHUT_WR) < 0)) ? -1 : 0) +#endif +#include + +#include "timeout.h" + +#if !defined(__STDC_VERSION__) || (__STDC_VERSION__ < 199901L) +# ifndef destructor +# define destructor __destructor__ +# endif +# ifndef constructor +# define constructor __constructor__ +# endif +# ifndef packed +# define packed __packed__ +# endif +# ifndef inline +# define inline __inline__ +# endif +# ifndef unused +# define unused __unused__ +# endif +# ifndef volatile +# define volatile __volatile__ +# endif +#endif +#ifndef attribute +# define attribute(attr) __attribute__(attr) +#endif + +#if defined __GNUC__ +# undef strcpy +# define strcpy(d,s) __builtin_strcpy((d),(s)) /* Without boundary check please */ +#endif + +/* + * The structure used for communication between the processes + */ +typedef struct _handle { + int errcode; + struct stat argument; + stat_t function; + size_t len; + char path[0]; +} attribute((packed)) handle_t; + +/* + * Using a forked process for doing e.g. stat(2) system call as this + * allows us to send e.g. SIGKILL to this process if it hangs in `D' + * state on a file share due a stalled NFS server. This does not work + * with (p)threads as SIGKILL would kill all threads including main. + */ + +static volatile pid_t active; +static int pipes[4] = {-1, -1, -1, -1}; +static char buf[PATH_MAX + sizeof(handle_t) + 1]; + +static void sigchild(int sig attribute((unused))) +{ + pid_t pid = waitpid(active, NULL, WNOHANG|WUNTRACED); + if (pid <= 0) + return; + if (errno == ECHILD) + return; + active = 0; +} + +static void attribute((constructor)) start(void) +{ + sigset_t sigset, oldset; + struct sigaction act; + ssize_t in; + + if (pipes[1] >= 0) close(pipes[1]); + if (pipes[2] >= 0) close(pipes[2]); + + if (pipe(&pipes[0])) + goto error; + if (pipe(&pipes[2])) + goto error; + + memset(&act, 0, sizeof(act)); + sigemptyset(&act.sa_mask); + act.sa_flags = SA_RESTART; + act.sa_handler = sigchild; + sigaction(SIGCHLD, &act, 0); + + if ((active = fork()) < 0) + goto error; + + if (active) { + close(pipes[0]); + close(pipes[3]); + pipes[0] = pipes[3] = -1; + return; + } + + sigemptyset(&sigset); + sigaddset(&sigset, SIGALRM); + sigprocmask(SIG_BLOCK, &sigset, &oldset); + + act.sa_handler = SIG_DFL; + sigaction(SIGCHLD, &act, 0); + + close(pipes[1]); + close(pipes[2]); + dup2(pipes[0], STDIN_FILENO); + dup2(pipes[3], STDOUT_FILENO); + close(pipes[0]); + close(pipes[3]); + pipes[1] = pipes[2] = -1; + pipes[0] = pipes[3] = -1; + + { + handle_t *restrict handle = (void*)&buf[0]; + + while ((in = read(STDIN_FILENO, handle, sizeof(buf))) > sizeof(handle_t)) { + if (handle->function(handle->path, &handle->argument) < 0) + handle->errcode = errno; + write(STDOUT_FILENO, &handle->errcode, sizeof(handle->errcode)+sizeof(handle->argument)); + memset(handle, 0, sizeof(handle_t)); + } + } + sigprocmask(SIG_SETMASK, &oldset, NULL); + exit(0); +error: + if (pipes[0] >= 0) close(pipes[0]); + if (pipes[1] >= 0) close(pipes[1]); + if (pipes[2] >= 0) close(pipes[2]); + if (pipes[3] >= 0) close(pipes[3]); +} + +static void /* attribute((destructor)) */ stop(void) +{ + if (active && waitpid(active, NULL, WNOHANG|WUNTRACED) == 0) + kill(active, SIGKILL); +} + +static sigjmp_buf jenv; +static void sigjump(int sig attribute((unused))) +{ + siglongjmp(jenv, 1); +} + +/* + * External routine + */ +int timeout(stat_t function, const char *path, struct stat *restrict argument, time_t seconds) +{ + handle_t *restrict handle = (void*)&buf[0]; + struct sigaction alrm_act, pipe_act, new_act; + sigset_t sigset, oldset; + + if (active <= 0) /* Oops, last one failed therefore clear status and restart */ + start(); + + memset(handle, 0, sizeof(handle_t)); + handle->len = strlen(path) + 1; + if (handle->len >= PATH_MAX) { + errno = ENAMETOOLONG; + goto error; + } + handle->errcode = 0; + handle->argument = *argument; + handle->function = function; + strcpy(handle->path, path); + + sigemptyset(&sigset); + sigaddset(&sigset, SIGALRM); + sigaddset(&sigset, SIGPIPE); + sigprocmask(SIG_UNBLOCK, &sigset, &oldset); + + memset(&new_act, 0, sizeof(new_act)); + sigemptyset(&new_act.sa_mask); + new_act.sa_flags = SA_RESETHAND; + + if (sigsetjmp(jenv, 1)) + goto timed; + + new_act.sa_handler = sigjump; + sigaction(SIGALRM, &new_act, &alrm_act); + sigaction(SIGPIPE, &new_act, &pipe_act); + alarm(seconds); + + write(pipes[1], handle, sizeof(handle_t)+handle->len); + read(pipes[2], &handle->errcode, sizeof(handle->errcode)+sizeof(handle->argument)); + + alarm(0); + sigaction(SIGPIPE, &pipe_act, NULL); + sigaction(SIGALRM, &alrm_act, NULL); + + if (handle->errcode) { + errno = handle->errcode; + goto error; + } + + *argument = handle->argument; + sigprocmask(SIG_SETMASK, &oldset, NULL); + + return 0; +timed: + (void) alarm(0); + sigaction(SIGPIPE, &pipe_act, NULL); + sigaction(SIGALRM, &alrm_act, NULL); + sigprocmask(SIG_SETMASK, &oldset, NULL); + stop(); + errno = ETIMEDOUT; +error: + return -1; +} + +/* + * End of timeout.c + */ diff --git a/src/timeout.h b/src/timeout.h new file mode 100644 index 0000000..546c13b --- /dev/null +++ b/src/timeout.h @@ -0,0 +1,36 @@ +/* + * timout.h Advanced timeout handling for file system calls + * to avoid deadlocks on remote file shares. + * + * Version: 0.1 07-Sep-2011 Fink + * + * Copyright 2011 Werner Fink, 2011 SUSE LINUX Products GmbH, Germany. + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; either version 2 of the License, or + * (at your option) any later version. + * + * Author: Werner Fink , 2011 + */ + +#ifndef _TIMEOUT_H +#define _TIMEOUT_H + +#include "config.h" /* For _FILE_OFFSET_BITS */ + +#include +#include +#include +#include + +#if !defined(__STDC_VERSION__) || (__STDC_VERSION__ < 199901L) +# ifndef restrict +# define restrict __restrict__ +# endif +#endif + +typedef int (*stat_t)(const char *, struct stat *restrict); +extern int timeout(stat_t, const char *, struct stat *restrict, time_t); + +#endif