From: "H.J. Lu via Libc-alpha" <libc-alpha@sourceware.org>
To: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Cc: GNU C Library <libc-alpha@sourceware.org>
Subject: Re: [PATCH 2/2] Add run-time chesk for indirect external access
Date: Thu, 7 Oct 2021 10:10:50 -0700 [thread overview]
Message-ID: <CAMe9rOqC0eLX0qWgbi3GgCtm4Wh_pKZVjmNZ0xiBfG-8kQetGw@mail.gmail.com> (raw)
In-Reply-To: <151a9b34-8247-8274-da59-cf16300d8c3b@linaro.org>
On Thu, Oct 7, 2021 at 9:58 AM Adhemerval Zanella
<adhemerval.zanella@linaro.org> wrote:
>
>
>
> On 03/08/2021 18:59, H.J. Lu via Libc-alpha wrote:
> > When performing symbol lookup for references in executable without
> > indirect external access:
> >
> > 1. Disallow copy relocations in executable against protected data symbols
> > in a shared object with indirect external access.
> > 2. Disallow non-zero symbol values of undefined function symbols in
> > executable, which are used as the function pointer, against protected
> > function symbols in a shared object with indirect external access.
>
> How hard would to add some testcases for both cases? To simplify we may
> want to build it iff binutins supports noindirect-extern-access.
I will submit followup patches with testcases from
users/hjl/indirect/master branch:
https://gitlab.com/x86-glibc/glibc/-/tree/users/hjl/indirect/master
including adding LD_DEBUG=protected to check copy relocations against
protected data and non-canonical reference to protected function.
> The rest LGTM, just a nit below due an ununsed variable.
>
> Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
>
> > ---
> > elf/dl-lookup.c | 5 ++++
> > sysdeps/generic/dl-protected.h | 54 ++++++++++++++++++++++++++++++++++
> > 2 files changed, 59 insertions(+)
> > create mode 100644 sysdeps/generic/dl-protected.h
> >
> > diff --git a/elf/dl-lookup.c b/elf/dl-lookup.c
> > index eea217eb28..430359af39 100644
> > --- a/elf/dl-lookup.c
> > +++ b/elf/dl-lookup.c
> > @@ -24,6 +24,7 @@
> > #include <ldsodefs.h>
> > #include <dl-hash.h>
> > #include <dl-machine.h>
> > +#include <dl-protected.h>
> > #include <sysdep-cancel.h>
> > #include <libc-lock.h>
> > #include <tls.h>
> > @@ -527,6 +528,10 @@ do_lookup_x (const char *undef_name, uint_fast32_t new_hash,
> > if (__glibc_unlikely (dl_symbol_visibility_binds_local_p (sym)))
> > goto skip;
> >
> > + if (ELFW(ST_VISIBILITY) (sym->st_other) == STV_PROTECTED)
> > + _dl_check_protected_symbol (undef_name, undef_map, ref, map,
> > + type_class);
> > +
> > switch (ELFW(ST_BIND) (sym->st_info))
> > {
> > case STB_WEAK:
>
> Ok.
>
> > diff --git a/sysdeps/generic/dl-protected.h b/sysdeps/generic/dl-protected.h
> > new file mode 100644
> > index 0000000000..244d020dc4
> > --- /dev/null
> > +++ b/sysdeps/generic/dl-protected.h
> > @@ -0,0 +1,54 @@
> > +/* Support for STV_PROTECTED visibility. Generic version.
> > + Copyright (C) 2021 Free Software Foundation, Inc.
> > + This file is part of the GNU C Library.
> > +
> > + The GNU C Library is free software; you can redistribute it and/or
> > + modify it under the terms of the GNU Lesser General Public
> > + License as published by the Free Software Foundation; either
> > + version 2.1 of the License, or (at your option) any later version.
> > +
> > + The GNU C Library is distributed in the hope that it will be useful,
> > + but WITHOUT ANY WARRANTY; without even the implied warranty of
> > + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
> > + Lesser General Public License for more details.
> > +
> > + You should have received a copy of the GNU Lesser General Public
> > + License along with the GNU C Library; if not, see
> > + <https://www.gnu.org/licenses/>. */
> > +
> > +#ifndef _DL_PROTECTED_H
> > +#define _DL_PROTECTED_H
> > +
> > +static inline void __attribute__ ((always_inline))
> > +_dl_check_protected_symbol (const char *undef_name,
>
> This argument seems unused.
It is used in
_dl_signal_error (0, map->l_name, undef_name,
N_("non-canonical reference to canonical
protected function"));
> > + const struct link_map *undef_map,
> > + const ElfW(Sym) *ref,
> > + const struct link_map *map,
> > + int type_class)
> > +{
> > + if (undef_map != NULL
> > + && undef_map->l_type == lt_executable
> > + && !(undef_map->l_1_needed
> > + & GNU_PROPERTY_1_NEEDED_INDIRECT_EXTERN_ACCESS)
> > + && (map->l_1_needed
> > + & GNU_PROPERTY_1_NEEDED_INDIRECT_EXTERN_ACCESS))
> > + {
> > + if ((type_class & ELF_RTYPE_CLASS_COPY))
> > + /* Disallow copy relocations in executable against protected
> > + data symbols in a shared object which needs indirect external
> > + access. */
> > + _dl_signal_error (0, map->l_name, undef_name,
> > + N_("copy relocation against non-copyable protected symbol"));
> > + else if (ref->st_value != 0
> > + && ref->st_shndx == SHN_UNDEF
> > + && (type_class & ELF_RTYPE_CLASS_PLT))
> > + /* Disallow non-zero symbol values of undefined symbols in
> > + executable, which are used as the function pointer, against
> > + protected function symbols in a shared object with indirect
> > + external access. */
> > + _dl_signal_error (0, map->l_name, undef_name,
> > + N_("non-canonical reference to canonical protected function"));
> > + }
> > +}
> > +
> > +#endif /* _DL_PROTECTED_H */
> >
>
> Ok.
I will check it in ASIS.
Thanks.
--
H.J.
next prev parent reply other threads:[~2021-10-07 17:11 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-03 21:59 [PATCH 1/2] Initial support for GNU_PROPERTY_1_NEEDED H.J. Lu via Libc-alpha
2021-08-03 21:59 ` [PATCH 2/2] Add run-time chesk for indirect external access H.J. Lu via Libc-alpha
2021-09-27 2:10 ` PING^1 " H.J. Lu via Libc-alpha
2021-10-07 16:58 ` Adhemerval Zanella via Libc-alpha
2021-10-07 17:10 ` H.J. Lu via Libc-alpha [this message]
2021-10-07 17:45 ` Adhemerval Zanella via Libc-alpha
2021-10-07 14:53 ` [PATCH 1/2] Initial support for GNU_PROPERTY_1_NEEDED Adhemerval Zanella via Libc-alpha
2021-10-07 15:11 ` H.J. Lu via Libc-alpha
2021-10-07 16:53 ` Adhemerval Zanella via Libc-alpha
2021-10-07 17:04 ` H.J. Lu via Libc-alpha
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