Commit 604b96de authored by Ramon Nou's avatar Ramon Nou
Browse files

control vfork on libc

parent c29b3098

src/client/gkfs_libc.cpp

+48 −26
Original line number Diff line number Diff line
@@ -303,37 +303,59 @@ DLSYM_WRAPPER(int, closedir, (DIR * dirp), (dirp), "closedir") 
DLSYM_WRAPPER(void, seekdir, (DIR * dirp, long loc), (dirp, loc), "seekdir")

DLSYM_WRAPPER(long, telldir, (DIR * dirp), (dirp), "telldir")



static int (*real_fork)(void) = nullptr;

int

dlsym_fork(void) {

    if(!real_fork) {

        real_fork =

                reinterpret_cast<int (*)(void)>(dlsym(((void*) -1l), "fork"));

        if(!real_fork) {

            fprintf(stderr, "dlsym failed for %s: %s\n", "fork", dlerror());

            (*__errno_location()) = 38;

            return (int) -1;

        }

    }

    log_arguments("fork");

    return real_fork();

}

static int (*real_vfork)(void) = nullptr;

int

dlsym_vfork(void) {

    if(!real_vfork) {



static pid_t (*real_fork)(void) = NULL;

static pid_t (*real_vfork)(void) = NULL;

static pid_t (*real_clone)(int (*fn)(void*), void*, int, void*, ...) = NULL;





/*pid_t fork(void) {

    if (!real_fork) reinterpret_cast<int (*)(void)>(dlsym(((void*) -1l),

"fork"));



    destroy_libc();

    pid_t pid = real_fork();

    (pid == 0) ? init_libc() : init_libc();

    return pid;

}*/



pid_t

vfork(void) {

    if(!real_vfork)

        real_vfork =

                reinterpret_cast<int (*)(void)>(dlsym(((void*) -1l), "vfork"));

        if(!real_vfork) {

            fprintf(stderr, "dlsym failed for %s: %s\n", "vfork", dlerror());

            (*__errno_location()) = 38;

            return (int) -1;



    destroy_libc();

    pid_t pid = real_vfork();

    // vfork child shares memory until execve, so:

    if(pid == 0) {

        init_libc(); // Dangerous! Must be async-signal-safe

    } else {

        init_libc();

    }

    return pid;

}

    log_arguments("vfork");

    return real_vfork();



pid_t

clone(int (*fn)(void*), void* stack, int flags, void* arg, ...) {

    if(!real_clone)

        real_clone =

                reinterpret_cast<decltype(&::clone)>(dlsym(RTLD_NEXT, "clone"));



    // Only handle process-creation clones

    if(flags & (SIGCHLD | CLONE_VFORK)) {

        destroy_libc();

    }



    pid_t pid = real_clone(fn, stack, flags, arg);



    if(flags & (SIGCHLD | CLONE_VFORK)) {

        (pid == 0) ? init_libc() : init_libc();

    }

    return pid;

}





DLSYM_WRAPPER(int, pipe, (int pipefd[2]), (pipefd), "pipe")

DLSYM_WRAPPER(int, dup, (int fd), (fd), "dup")

DLSYM_WRAPPER(int, dup2, (int fd, int fd2), (fd, fd2), "dup2")

src/client/preload.cpp

+2 −4
Original line number Diff line number Diff line
@@ -359,8 +359,7 @@ init_preload() { 
    // The original errno value will be restored after initialization to not

    // leak internal error codes

    auto oerrno = errno;

    if(!init) {

        init = true;

    if (atomic_exchange(&init, 1) == 0) {

        pthread_atfork(&at_fork_syscall, &at_parent_syscall, &at_child_syscall);

    }

    CTX->enable_interception();
@@ -515,8 +514,7 @@ init_libc() { 
        CTX->protect_user_fds();

    }



    if(!init) {

        init = true;

    if (atomic_exchange(&init, 1) == 0) {

        pthread_atfork(&at_fork, &at_parent, &at_child);

    }