#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)
{
- return syscall(SYS_faccessat, fd, filename, amode, 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);
}