posix: Improve default posix_spawn implementation
This patch improves the default posix implementation of posix_spawn{p} and align with Linux one. The main idea is to fix some issues already fixed in Linux code, and deprecated vfork internal usage (source of various bug reports). In a short: - It moves POSIX_SPAWN_USEVFORK usage and sets it a no-op. Since the process that actually spawn the new process do not share memory with parent (with vfork), it fixes BZ#14750 for this implementation. - It uses a pipe to correctly obtain the return upon failure of execution (BZ#18433). - It correctly enable/disable asynchronous cancellation (checked on ptl/tst-exec5.c). - It correctly disable/enable signal handling. Using this version instead of Linux shows only one regression, posix/tst-spawn3, because of pipe2 usage which increase total number of file descriptor. * sysdeps/posix/spawni.c (__spawni_child): New function. (__spawni): Rename to __spawnix.
This commit is contained in:
parent
edc1686af0
commit
ccfb296472
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@ -1,3 +1,8 @@
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2017-06-29 Adhemerval Zanella <adhemerval.zanella@linaro.org>
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* sysdeps/posix/spawni.c (__spawni_child): New function.
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(__spawni): Rename to __spawnix.
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2017-06-29 Florian Weimer <fweimer@redhat.com>
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* stdio-common/vfprintf.c (group_number): Add front_ptr argument.
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@ -16,20 +16,23 @@
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License along with the GNU C Library; if not, see
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<http://www.gnu.org/licenses/>. */
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#include <errno.h>
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#include <spawn.h>
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#include <assert.h>
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#include <fcntl.h>
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#include <paths.h>
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#include <spawn.h>
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#include <stdbool.h>
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#include <stdlib.h>
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#include <string.h>
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#include <unistd.h>
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#include <signal.h>
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#include <sys/resource.h>
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#include "spawn_int.h"
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#include <sys/wait.h>
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#include <sys/param.h>
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#include <sys/mman.h>
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#include <not-cancel.h>
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#include <local-setxid.h>
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#include <shlib-compat.h>
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#include <nptl/pthreadP.h>
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#include <dl-sysdep.h>
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#include <libc-pointer-arith.h>
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#include <ldsodefs.h>
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#include "spawn_int.h"
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/* The Unix standard contains a long explanation of the way to signal
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@ -39,94 +42,59 @@
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normal program exit with the exit code 127. */
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#define SPAWN_ERROR 127
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struct posix_spawn_args
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{
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sigset_t oldmask;
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const char *file;
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int (*exec) (const char *, char *const *, char *const *);
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const posix_spawn_file_actions_t *fa;
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const posix_spawnattr_t *restrict attr;
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char *const *argv;
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ptrdiff_t argc;
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char *const *envp;
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int xflags;
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int pipe[2];
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};
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/* The file is accessible but it is not an executable file. Invoke
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the shell to interpret it as a script. */
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/* Older version requires that shell script without shebang definition
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to be called explicitly using /bin/sh (_PATH_BSHELL). */
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static void
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internal_function
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script_execute (const char *file, char *const argv[], char *const envp[])
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{
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/* Count the arguments. */
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int argc = 0;
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while (argv[argc++])
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;
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/* Construct an argument list for the shell. */
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{
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char *new_argv[argc + 1];
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new_argv[0] = (char *) _PATH_BSHELL;
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new_argv[1] = (char *) file;
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while (argc > 1)
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{
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new_argv[argc] = argv[argc - 1];
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--argc;
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}
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/* Execute the shell. */
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__execve (new_argv[0], new_argv, envp);
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}
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}
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static inline void
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maybe_script_execute (const char *file, char *const argv[], char *const envp[],
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int xflags)
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maybe_script_execute (struct posix_spawn_args *args)
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{
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if (SHLIB_COMPAT (libc, GLIBC_2_2, GLIBC_2_15)
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&& (xflags & SPAWN_XFLAGS_TRY_SHELL)
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&& errno == ENOEXEC)
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script_execute (file, argv, envp);
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}
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/* Spawn a new process executing PATH with the attributes describes in *ATTRP.
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Before running the process perform the actions described in FILE-ACTIONS. */
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int
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__spawni (pid_t *pid, const char *file,
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const posix_spawn_file_actions_t *file_actions,
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const posix_spawnattr_t *attrp, char *const argv[],
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char *const envp[], int xflags)
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&& (args->xflags & SPAWN_XFLAGS_TRY_SHELL) && errno == ENOEXEC)
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{
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pid_t new_pid;
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char *path, *p, *name;
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size_t len;
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size_t pathlen;
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char *const *argv = args->argv;
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ptrdiff_t argc = args->argc;
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/* Do this once. */
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short int flags = attrp == NULL ? 0 : attrp->__flags;
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/* Generate the new process. */
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if ((flags & POSIX_SPAWN_USEVFORK) != 0
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/* If no major work is done, allow using vfork. Note that we
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might perform the path searching. But this would be done by
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a call to execvp(), too, and such a call must be OK according
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to POSIX. */
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|| ((flags & (POSIX_SPAWN_SETSIGMASK | POSIX_SPAWN_SETSIGDEF
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| POSIX_SPAWN_SETSCHEDPARAM | POSIX_SPAWN_SETSCHEDULER
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| POSIX_SPAWN_SETPGROUP | POSIX_SPAWN_RESETIDS
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| POSIX_SPAWN_SETSID)) == 0
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&& file_actions == NULL))
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new_pid = __vfork ();
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/* Construct an argument list for the shell. */
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char *new_argv[argc + 1];
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new_argv[0] = (char *) _PATH_BSHELL;
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new_argv[1] = (char *) args->file;
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if (argc > 1)
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memcpy (new_argv + 2, argv + 1, argc * sizeof(char *));
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else
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new_pid = __fork ();
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new_argv[2] = NULL;
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if (new_pid != 0)
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{
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if (new_pid < 0)
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return errno;
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/* The call was successful. Store the PID if necessary. */
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if (pid != NULL)
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*pid = new_pid;
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return 0;
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/* Execute the shell. */
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args->exec (new_argv[0], new_argv, args->envp);
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}
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}
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/* Set signal mask. */
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if ((flags & POSIX_SPAWN_SETSIGMASK) != 0
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&& __sigprocmask (SIG_SETMASK, &attrp->__ss, NULL) != 0)
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_exit (SPAWN_ERROR);
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/* Function used in the clone call to setup the signals mask, posix_spawn
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attributes, and file actions. */
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static int
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__spawni_child (void *arguments)
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{
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struct posix_spawn_args *args = arguments;
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const posix_spawnattr_t *restrict attr = args->attr;
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const posix_spawn_file_actions_t *file_actions = args->fa;
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int ret;
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__close (args->pipe[0]);
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/* Set signal default action. */
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if ((flags & POSIX_SPAWN_SETSIGDEF) != 0)
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if ((attr->__flags & POSIX_SPAWN_SETSIGDEF) != 0)
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{
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/* We have to iterate over all signals. This could possibly be
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done better but it requires system specific solutions since
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sa.sa_handler = SIG_DFL;
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for (sig = 1; sig <= _NSIG; ++sig)
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if (__sigismember (&attrp->__sd, sig) != 0
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if (__sigismember (&attr->__sd, sig) != 0
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&& __sigaction (sig, &sa, NULL) != 0)
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_exit (SPAWN_ERROR);
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goto fail;
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}
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#ifdef _POSIX_PRIORITY_SCHEDULING
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/* Set the scheduling algorithm and parameters. */
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if ((flags & (POSIX_SPAWN_SETSCHEDPARAM | POSIX_SPAWN_SETSCHEDULER))
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if ((attr->__flags & (POSIX_SPAWN_SETSCHEDPARAM | POSIX_SPAWN_SETSCHEDULER))
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== POSIX_SPAWN_SETSCHEDPARAM)
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{
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if (__sched_setparam (0, &attrp->__sp) == -1)
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_exit (SPAWN_ERROR);
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if ((ret = __sched_setparam (0, &attr->__sp)) == -1)
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goto fail;
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}
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else if ((flags & POSIX_SPAWN_SETSCHEDULER) != 0)
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else if ((attr->__flags & POSIX_SPAWN_SETSCHEDULER) != 0)
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{
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if (__sched_setscheduler (0, attrp->__policy, &attrp->__sp) == -1)
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_exit (SPAWN_ERROR);
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if ((ret = __sched_setscheduler (0, attr->__policy, &attr->__sp) == -1))
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goto fail;
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}
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#endif
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if ((flags & POSIX_SPAWN_SETSID) != 0
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&& __setsid () < 0)
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_exit (SPAWN_ERROR);
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/* Set the process session ID. */
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if ((attr->__flags & POSIX_SPAWN_SETSID) != 0
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&& (ret = __setsid ()) < 0)
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goto fail;
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/* Set the process group ID. */
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if ((flags & POSIX_SPAWN_SETPGROUP) != 0
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&& __setpgid (0, attrp->__pgrp) != 0)
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_exit (SPAWN_ERROR);
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if ((attr->__flags & POSIX_SPAWN_SETPGROUP) != 0
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&& (ret =__setpgid (0, attr->__pgrp)) != 0)
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goto fail;
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/* Set the effective user and group IDs. */
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if ((flags & POSIX_SPAWN_RESETIDS) != 0
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&& (local_seteuid (__getuid ()) != 0
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|| local_setegid (__getgid ()) != 0))
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_exit (SPAWN_ERROR);
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if ((attr->__flags & POSIX_SPAWN_RESETIDS) != 0
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&& ((ret = local_seteuid (__getuid ())) != 0
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|| (ret = local_setegid (__getgid ())) != 0))
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goto fail;
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/* Execute the file actions. */
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if (file_actions != NULL)
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case spawn_do_close:
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if (close_not_cancel (action->action.close_action.fd) != 0)
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{
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if (! have_fdlimit)
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if (have_fdlimit == 0)
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{
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__getrlimit64 (RLIMIT_NOFILE, &fdlimit);
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have_fdlimit = true;
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/* Only signal errors for file descriptors out of range. */
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if (action->action.close_action.fd < 0
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|| action->action.close_action.fd >= fdlimit.rlim_cur)
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/* Signal the error. */
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_exit (SPAWN_ERROR);
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{
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ret = -1;
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goto fail;
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}
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}
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break;
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case spawn_do_open:
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{
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/* POSIX states that if fildes was already an open file descriptor,
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it shall be closed before the new file is opened. This avoid
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pontential issues when posix_spawn plus addopen action is called
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with the process already at maximum number of file descriptor
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opened and also for multiple actions on single-open special
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paths (like /dev/watchdog). */
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close_not_cancel (action->action.open_action.fd);
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int new_fd = open_not_cancel (action->action.open_action.path,
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action->action.open_action.oflag
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| O_LARGEFILE,
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action->action.open_action.mode);
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if (new_fd == -1)
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/* The `open' call failed. */
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_exit (SPAWN_ERROR);
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if ((ret = new_fd) == -1)
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goto fail;
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/* Make sure the desired file descriptor is used. */
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if (new_fd != action->action.open_action.fd)
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{
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if (__dup2 (new_fd, action->action.open_action.fd)
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if ((ret = __dup2 (new_fd, action->action.open_action.fd))
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!= action->action.open_action.fd)
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/* The `dup2' call failed. */
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_exit (SPAWN_ERROR);
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goto fail;
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if (close_not_cancel (new_fd) != 0)
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/* The `close' call failed. */
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_exit (SPAWN_ERROR);
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if ((ret = close_not_cancel (new_fd) != 0))
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goto fail;
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}
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}
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break;
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case spawn_do_dup2:
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if (__dup2 (action->action.dup2_action.fd,
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action->action.dup2_action.newfd)
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if ((ret = __dup2 (action->action.dup2_action.fd,
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action->action.dup2_action.newfd))
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!= action->action.dup2_action.newfd)
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/* The `dup2' call failed. */
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_exit (SPAWN_ERROR);
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goto fail;
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break;
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}
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}
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}
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if ((xflags & SPAWN_XFLAGS_USE_PATH) == 0 || strchr (file, '/') != NULL)
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{
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/* The FILE parameter is actually a path. */
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__execve (file, argv, envp);
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/* Set the initial signal mask of the child if POSIX_SPAWN_SETSIGMASK
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is set, otherwise restore the previous one. */
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__sigprocmask (SIG_SETMASK, (attr->__flags & POSIX_SPAWN_SETSIGMASK)
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? &attr->__ss : &args->oldmask, 0);
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maybe_script_execute (file, argv, envp, xflags);
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args->exec (args->file, args->argv, args->envp);
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/* This is compatibility function required to enable posix_spawn run
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script without shebang definition for older posix_spawn versions
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(2.15). */
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maybe_script_execute (args);
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ret = -errno;
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fail:
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/* Since sizeof errno < PIPE_BUF, the write is atomic. */
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ret = -ret;
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if (ret)
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while (write_not_cancel (args->pipe[1], &ret, sizeof (ret)) < 0);
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/* Oh, oh. `execve' returns. This is bad. */
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_exit (SPAWN_ERROR);
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}
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/* We have to search for FILE on the path. */
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path = getenv ("PATH");
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if (path == NULL)
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/* Spawn a new process executing PATH with the attributes describes in *ATTRP.
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Before running the process perform the actions described in FILE-ACTIONS. */
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int
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__spawnix (pid_t *pid, const char *file,
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const posix_spawn_file_actions_t *file_actions,
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const posix_spawnattr_t *attrp, char *const argv[],
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char *const envp[], int xflags,
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int (*exec) (const char *, char *const *, char *const *))
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{
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/* There is no `PATH' in the environment.
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The default search path is the current directory
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followed by the path `confstr' returns for `_CS_PATH'. */
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len = confstr (_CS_PATH, (char *) NULL, 0);
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path = (char *) __alloca (1 + len);
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path[0] = ':';
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(void) confstr (_CS_PATH, path + 1, len);
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struct posix_spawn_args args;
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int ec;
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if (__pipe2 (args.pipe, O_CLOEXEC))
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return errno;
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/* Disable asynchronous cancellation. */
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int state;
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__libc_ptf_call (__pthread_setcancelstate,
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(PTHREAD_CANCEL_DISABLE, &state), 0);
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ptrdiff_t argc = 0;
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ptrdiff_t limit = INT_MAX - 1;
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while (argv[argc++] != NULL)
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if (argc == limit)
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{
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errno = E2BIG;
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return errno;
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}
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len = strlen (file) + 1;
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pathlen = strlen (path);
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name = __alloca (pathlen + len + 1);
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/* Copy the file name at the top. */
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name = (char *) memcpy (name + pathlen + 1, file, len);
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/* And add the slash. */
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*--name = '/';
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args.file = file;
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args.exec = exec;
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args.fa = file_actions;
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args.attr = attrp ? attrp : &(const posix_spawnattr_t) { 0 };
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args.argv = argv;
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args.argc = argc;
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args.envp = envp;
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args.xflags = xflags;
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p = path;
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do
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/* Generate the new process. */
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pid_t new_pid = __fork ();
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if (new_pid == 0)
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__spawni_child (&args);
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else if (new_pid > 0)
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{
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char *startp;
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__close (args.pipe[1]);
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path = p;
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p = __strchrnul (path, ':');
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if (p == path)
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/* Two adjacent colons, or a colon at the beginning or the end
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of `PATH' means to search the current directory. */
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startp = name + 1;
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if (__read (args.pipe[0], &ec, sizeof ec) != sizeof ec)
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ec = 0;
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else
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startp = (char *) memcpy (name - (p - path), path, p - path);
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__waitpid (new_pid, &(int) { 0 }, 0);
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}
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else
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ec = -new_pid;
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/* Try to execute this name. If it works, execv will not return. */
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__execve (startp, argv, envp);
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__close (args.pipe[0]);
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maybe_script_execute (startp, argv, envp, xflags);
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if ((ec == 0) && (pid != NULL))
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*pid = new_pid;
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switch (errno)
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__libc_ptf_call (__pthread_setcancelstate, (state, NULL), 0);
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return ec;
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}
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int
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__spawni (pid_t * pid, const char *file,
|
||||
const posix_spawn_file_actions_t * acts,
|
||||
const posix_spawnattr_t * attrp, char *const argv[],
|
||||
char *const envp[], int xflags)
|
||||
{
|
||||
case EACCES:
|
||||
case ENOENT:
|
||||
case ESTALE:
|
||||
case ENOTDIR:
|
||||
/* Those errors indicate the file is missing or not executable
|
||||
by us, in which case we want to just try the next path
|
||||
directory. */
|
||||
break;
|
||||
|
||||
default:
|
||||
/* Some other error means we found an executable file, but
|
||||
something went wrong executing it; return the error to our
|
||||
caller. */
|
||||
_exit (SPAWN_ERROR);
|
||||
}
|
||||
}
|
||||
while (*p++ != '\0');
|
||||
|
||||
/* Return with an error. */
|
||||
_exit (SPAWN_ERROR);
|
||||
return __spawnix (pid, file, acts, attrp, argv, envp, xflags,
|
||||
xflags & SPAWN_XFLAGS_USE_PATH ? __execvpe : __execve);
|
||||
}
|
||||
|
|
Loading…
Reference in New Issue