| #include <unistd.h> |
| #include <fcntl.h> |
| #include <errno.h> |
| #include <sys/wait.h> |
| #include "syscall.h" |
| #include "pthread_impl.h" |
| |
| struct ctx { |
| int fd; |
| const char *filename; |
| int amode; |
| }; |
| |
| static const int errors[] = { |
| 0, -EACCES, -ELOOP, -ENAMETOOLONG, -ENOENT, -ENOTDIR, |
| -EROFS, -EBADF, -EINVAL, -ETXTBSY, |
| -EFAULT, -EIO, -ENOMEM, |
| -EBUSY |
| }; |
| |
| static int checker(void *p) |
| { |
| struct ctx *c = p; |
| int ret; |
| int i; |
| if (__syscall(SYS_setregid, __syscall(SYS_getegid), -1) |
| || __syscall(SYS_setreuid, __syscall(SYS_geteuid), -1)) |
| __syscall(SYS_exit, 1); |
| ret = __syscall(SYS_faccessat, c->fd, c->filename, c->amode, 0); |
| for (i=0; i < sizeof errors/sizeof *errors - 1 && ret!=errors[i]; i++); |
| return i; |
| } |
| |
| int faccessat(int fd, const char *filename, int amode, int flag) |
| { |
| if (!flag || (flag==AT_EACCESS && getuid()==geteuid() && getgid()==getegid())) |
| return syscall(SYS_faccessat, fd, filename, amode, flag); |
| |
| if (flag != AT_EACCESS) |
| return __syscall_ret(-EINVAL); |
| |
| char stack[1024]; |
| sigset_t set; |
| pid_t pid; |
| int ret = -EBUSY; |
| struct ctx c = { .fd = fd, .filename = filename, .amode = amode }; |
| |
| __block_all_sigs(&set); |
| |
| pid = __clone(checker, stack+sizeof stack, 0, &c); |
| if (pid > 0) { |
| int status; |
| do { |
| __syscall(SYS_wait4, pid, &status, __WCLONE, 0); |
| } while (!WIFEXITED(status) && !WIFSIGNALED(status)); |
| if (WIFEXITED(status)) |
| ret = errors[WEXITSTATUS(status)]; |
| } |
| |
| __restore_sigs(&set); |
| |
| return __syscall_ret(ret); |
| } |