On Thu, Jun 4, 2020 at 10:43 AM <glider@xxxxxxxxxx> wrote: > > Under certain circumstances (we found this out running Docker on a > Clang-built kernel with CONFIG_INIT_STACK_ALL) ovl_copy_xattr() may > return uninitialized value of |error| from ovl_copy_xattr(). > It is then returned by ovl_create() to lookup_open(), which casts it to > an invalid dentry pointer, that can be further read or written by the > lookup_open() callers. > > The uninitialized value is returned when all the xattr on the file > are ovl_is_private_xattr(), which is actually a successful case, > therefore we initialize |error| with 0. > > Signed-off-by: Alexander Potapenko <glider@xxxxxxxxxx> > Cc: Kees Cook <keescook@xxxxxxxxxxxx> > Cc: Roy Yang <royyang@xxxxxxxxxx> > Cc: <stable@xxxxxxxxxxxxxxx> # 4.1 > > --- > > The bug seem to date back to at least v4.1 where the annotation has been > introduced (i.e. the compilers started noticing error could be used > before being initialized). I hovever didn't try to prove that the > problem is actually reproducible on such ancient kernels. We've seen it > on a real machine running v4.4 as well. > > v2: > -- Per Vivek Goyal's suggestion, changed |error| to be 0 Thanks, applied patch posted here (with your signed-off as well, since the patch is the same...): https://lore.kernel.org/linux-unionfs/874ks212uj.fsf@m5Zedd9JOGzJrf0/ Miklos
