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-rw-r--r--src/process/fdop.h2
-rw-r--r--src/process/posix_spawn.c174
-rw-r--r--src/process/posix_spawn_file_actions_adddup2.c4
3 files changed, 125 insertions, 55 deletions
diff --git a/src/process/fdop.h b/src/process/fdop.h
index 02ff83c5..00b87514 100644
--- a/src/process/fdop.h
+++ b/src/process/fdop.h
@@ -4,7 +4,7 @@
struct fdop {
struct fdop *next, *prev;
- int cmd, fd, newfd, oflag;
+ int cmd, fd, srcfd, oflag;
mode_t mode;
char path[];
};
diff --git a/src/process/posix_spawn.c b/src/process/posix_spawn.c
index 5eb516b0..c55907d3 100644
--- a/src/process/posix_spawn.c
+++ b/src/process/posix_spawn.c
@@ -1,51 +1,47 @@
+#define _GNU_SOURCE
#include <spawn.h>
+#include <sched.h>
#include <unistd.h>
#include <signal.h>
-#include <stdint.h>
#include <fcntl.h>
+#include <sys/wait.h>
#include "syscall.h"
#include "pthread_impl.h"
#include "fdop.h"
#include "libc.h"
-extern char **environ;
-
static void dummy_0()
{
}
weak_alias(dummy_0, __acquire_ptc);
weak_alias(dummy_0, __release_ptc);
-pid_t __vfork(void);
-
-int __posix_spawnx(pid_t *restrict res, const char *restrict path,
- int (*exec)(const char *, char *const *, char *const *),
- const posix_spawn_file_actions_t *fa,
- const posix_spawnattr_t *restrict attr,
- char *const argv[restrict], char *const envp[restrict])
-{
- pid_t pid;
+struct args {
+ int p[2];
sigset_t oldmask;
- int i;
- posix_spawnattr_t dummy_attr = { 0 };
-
- if (!attr) attr = &dummy_attr;
-
- sigprocmask(SIG_BLOCK, SIGALL_SET, &oldmask);
-
- __acquire_ptc();
- pid = __vfork();
-
- if (pid) {
- __release_ptc();
- sigprocmask(SIG_SETMASK, &oldmask, 0);
- if (pid < 0) return -pid;
- *res = pid;
- return 0;
- }
-
- for (i=1; i<=8*__SYSCALL_SSLEN; i++) {
- struct sigaction sa;
+ const char *path;
+ int (*exec)(const char *, char *const *, char *const *);
+ const posix_spawn_file_actions_t *fa;
+ const posix_spawnattr_t *restrict attr;
+ char *const *argv, *const *envp;
+};
+
+static int child(void *args_vp)
+{
+ int i, ret;
+ struct sigaction sa;
+ struct args *args = args_vp;
+ int p = args->p[1];
+ const posix_spawn_file_actions_t *fa = args->fa;
+ const posix_spawnattr_t *restrict attr = args->attr;
+
+ close(args->p[0]);
+
+ /* All signal dispositions must be either SIG_DFL or SIG_IGN
+ * before signals are unblocked. Otherwise a signal handler
+ * from the parent might get run in the child while sharing
+ * memory, with unpredictable and dangerous results. */
+ for (i=1; i<_NSIG; i++) {
__libc_sigaction(i, 0, &sa);
if (sa.sa_handler!=SIG_DFL && (sa.sa_handler!=SIG_IGN ||
((attr->__flags & POSIX_SPAWN_SETSIGDEF)
@@ -55,50 +51,124 @@ int __posix_spawnx(pid_t *restrict res, const char *restrict path,
}
}
- if ((attr->__flags&POSIX_SPAWN_SETPGROUP) && setpgid(0, attr->__pgrp))
- _exit(127);
+ if (attr->__flags & POSIX_SPAWN_SETPGROUP)
+ if ((ret=__syscall(SYS_setpgid, 0, attr->__pgrp)))
+ goto fail;
- /* Use syscalls directly because pthread state is not consistent
- * for making calls to the library wrappers... */
- if ((attr->__flags&POSIX_SPAWN_RESETIDS) && (
- __syscall(SYS_setgid, __syscall(SYS_getgid)) ||
- __syscall(SYS_setuid, __syscall(SYS_getuid)) ))
- _exit(127);
+ /* Use syscalls directly because pthread state because the
+ * library functions attempt to do a multi-threaded synchronized
+ * id-change, which would trash the parent's state. */
+ if (attr->__flags & POSIX_SPAWN_RESETIDS)
+ if ((ret=__syscall(SYS_setgid, __syscall(SYS_getgid))) ||
+ (ret=__syscall(SYS_setuid, __syscall(SYS_getuid))) )
+ goto fail;
if (fa && fa->__actions) {
struct fdop *op;
- int ret, fd;
+ int fd;
for (op = fa->__actions; op->next; op = op->next);
for (; op; op = op->prev) {
+ /* It's possible that a file operation would clobber
+ * the pipe fd used for synchronizing with the
+ * parent. To avoid that, we dup the pipe onto
+ * an unoccupied fd. */
+ if (op->fd == p) {
+ ret = __syscall(SYS_dup, p);
+ if (ret < 0) goto fail;
+ __syscall(SYS_close, p);
+ p = ret;
+ }
switch(op->cmd) {
case FDOP_CLOSE:
- ret = __syscall(SYS_close, op->fd);
+ if ((ret=__syscall(SYS_close, op->fd)))
+ goto fail;
break;
case FDOP_DUP2:
- ret = __syscall(SYS_dup2, op->fd, op->newfd)<0;
+ if ((ret=__syscall(SYS_dup2, op->srcfd, op->fd))<0)
+ goto fail;
break;
case FDOP_OPEN:
fd = __syscall(SYS_open, op->path,
op->oflag | O_LARGEFILE, op->mode);
- if (fd == op->fd) {
- ret = 0;
- } else {
- ret = __syscall(SYS_dup2, fd, op->fd)<0;
+ if ((ret=fd) < 0) goto fail;
+ if (fd != op->fd) {
+ if ((ret=__syscall(SYS_dup2, fd, op->fd))<0)
+ goto fail;
__syscall(SYS_close, fd);
}
break;
}
- if (ret) _exit(127);
}
}
- sigprocmask(SIG_SETMASK, (attr->__flags & POSIX_SPAWN_SETSIGMASK)
- ? &attr->__mask : &oldmask, 0);
+ /* Close-on-exec flag may have been lost if we moved the pipe
+ * to a different fd. We don't use F_DUPFD_CLOEXEC above because
+ * it would fail on older kernels and atomicity is not needed --
+ * in this process there are no threads or signal handlers. */
+ __syscall(SYS_fcntl, p, F_SETFD, FD_CLOEXEC);
- exec(path, argv, envp ? envp : environ);
+ pthread_sigmask(SIG_SETMASK, (attr->__flags & POSIX_SPAWN_SETSIGMASK)
+ ? &attr->__mask : &args->oldmask, 0);
+
+ args->exec(args->path, args->argv, args->envp);
+
+fail:
+ /* Since sizeof errno < PIPE_BUF, the write is atomic. */
+ ret = -ret;
+ if (ret) while (write(p, &ret, sizeof ret) < 0);
_exit(127);
+}
+
+
+int __posix_spawnx(pid_t *restrict res, const char *restrict path,
+ int (*exec)(const char *, char *const *, char *const *),
+ const posix_spawn_file_actions_t *fa,
+ const posix_spawnattr_t *restrict attr,
+ char *const argv[restrict], char *const envp[restrict])
+{
+ pid_t pid;
+ char stack[1024];
+ int ec=0, cs;
+ struct args args;
+
+ if (pipe2(args.p, O_CLOEXEC))
+ return errno;
+
+ pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, &cs);
+
+ args.path = path;
+ args.exec = exec;
+ args.fa = fa;
+ args.attr = attr ? attr : &(const posix_spawnattr_t){0};
+ args.argv = argv;
+ args.envp = envp;
+ pthread_sigmask(SIG_BLOCK, SIGALL_SET, &args.oldmask);
+
+ /* This lock prevents setuid/setgid operations while the parent
+ * is sharing memory with the child. Situations where processes
+ * with different permissions share VM are fundamentally unsafe. */
+ __acquire_ptc();
+ pid = __clone(child, stack+sizeof stack, CLONE_VM|SIGCHLD, &args);
+ close(args.p[1]);
+
+ if (pid > 0) {
+ if (read(args.p[0], &ec, sizeof ec) < sizeof ec) ec = 0;
+ else waitpid(pid, &(int){0}, 0);
+ } else {
+ ec = -pid;
+ }
+
+ /* At this point, the child has either exited or successfully
+ * performed exec, so the lock may be released. */
+ __release_ptc();
+ close(args.p[0]);
+
+ if (!ec) *res = pid;
+
+ pthread_sigmask(SIG_SETMASK, &args.oldmask, 0);
+ pthread_setcancelstate(cs, 0);
- return 0;
+ return ec;
}
int posix_spawn(pid_t *restrict res, const char *restrict path,
diff --git a/src/process/posix_spawn_file_actions_adddup2.c b/src/process/posix_spawn_file_actions_adddup2.c
index 26f2c5cc..0367498f 100644
--- a/src/process/posix_spawn_file_actions_adddup2.c
+++ b/src/process/posix_spawn_file_actions_adddup2.c
@@ -3,13 +3,13 @@
#include <errno.h>
#include "fdop.h"
-int posix_spawn_file_actions_adddup2(posix_spawn_file_actions_t *fa, int fd, int newfd)
+int posix_spawn_file_actions_adddup2(posix_spawn_file_actions_t *fa, int srcfd, int fd)
{
struct fdop *op = malloc(sizeof *op);
if (!op) return ENOMEM;
op->cmd = FDOP_DUP2;
+ op->srcfd = srcfd;
op->fd = fd;
- op->newfd = newfd;
if ((op->next = fa->__actions)) op->next->prev = op;
op->prev = 0;
fa->__actions = op;
generated by cgit v1.2.3-70-g09d2 (git 2.46.0) at 2024-11-16 21:26:44 +0000