if (flags & FLAG_Z) {
if (!CFG_TOYBOX_LSM_NONE) {
- // In theory we can just openat(O_PATH|O_NOFOLLOW) and getcontext() on
- // that filehandle, but the kernel won't let us read this "metadata"
- // unless we have permission to read the data, so we do these elaborate
- // bug workarounds instead.
- if (S_ISLNK(new->st.st_mode) && !(toys.optflags & FLAG_L)) {
+ int fd;
+
+ // Why not just openat(O_PATH|(O_NOFOLLOW*!!(toys.optflags&FLAG_L))) and
+ // lsm_fget_context() on that filehandle? Because the kernel is broken,
+ // and won't let us read this "metadata" from the filehandle unless we
+ // have permission to read the data. We _can_ read the same data in
+ // by path, we just can't do it through an O_PATH filehandle, because
+ // reasons. So as a bug workaround for the broken kernel, we do it
+ // both ways.
+ //
+ // The O_NONBLOCK is there to avoid triggering automounting (there's
+ // a rush of nostalgia for you) on directories we don't descend into,
+ // which O_PATH would have done for us but see "the kernel is broken".
+ if (S_ISSOCK(new->st.st_mode) ||
+ (S_ISLNK(new->st.st_mode) && !(toys.optflags & FLAG_L)) ||
+ -1 == (fd = openat(dirtree_parentfd(new), new->name,
+ O_RDONLY|O_NONBLOCK|O_NOATIME)))
+ {
char *path;
// Wouldn't it be nice if the lsm functions worked like openat(),
- // fchmodat(), mknodat(), readlinkat()... but no, this is 1990's tech.
+ // fchmodat(), mknodat(), readlinkat() so we could do this without
+ // even O_PATH? But no, this is 1990's tech.
path = dirtree_path(new, 0);
lsm_lget_context(path, (char **)&new->extra);
free(path);
} else {
- // Why O_NONBLOCK? No idea. Why not O_PATH|O_NOFOLLOW? Kernel's broken.
- int fd = openat(dirtree_parentfd(new), new->name,
- O_RDONLY|O_NONBLOCK|O_NOATIME);
-
- if (fd != -1) lsm_fget_context(fd, (char **)&new->extra);
+ lsm_fget_context(fd, (char **)&new->extra);
close(fd);
}
}