linux-kernel - Re: [PATCH] x86: efi: avoid BUILD_BUG_ON() for non-constant p4d

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Date:   Fri, 5 Feb 2021 10:27:54 -0800
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     Borislav Petkov <bp@...en8.de>
Cc:     Nathan Chancellor <nathan@...nel.org>,
        Ard Biesheuvel <ardb@...nel.org>,
        Arvind Sankar <nivedita@...m.mit.edu>,
        Arnd Bergmann <arnd@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, X86 ML <x86@...nel.org>,
        Nathan Chancellor <natechancellor@...il.com>,
        Arnd Bergmann <arnd@...db.de>,
        Darren Hart <dvhart@...radead.org>,
        Andy Shevchenko <andy@...radead.org>,
        "H. Peter Anvin" <hpa@...or.com>,
        linux-efi <linux-efi@...r.kernel.org>,
        platform-driver-x86@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        clang-built-linux <clang-built-linux@...glegroups.com>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Kees Cook <keescook@...omium.org>
Subject: Re: [PATCH] x86: efi: avoid BUILD_BUG_ON() for non-constant p4d_index

On Fri, Feb 5, 2021 at 2:35 AM Borislav Petkov <bp@...en8.de> wrote:
>
> On Wed, Feb 03, 2021 at 11:51:48AM -0700, Nathan Chancellor wrote:
> > x86_64 all{mod,yes}config with clang are going to ship broken in 5.11.
>
> Dunno, it is still broken here even with those build assertions removed. And it
> ain't even an all{mod,yes}config - just my machine's config with
>
> CONFIG_ARCH_HAS_UBSAN_SANITIZE_ALL=y
> CONFIG_UBSAN=y
> # CONFIG_UBSAN_TRAP is not set
> CONFIG_CC_HAS_UBSAN_BOUNDS=y
> CONFIG_CC_HAS_UBSAN_ARRAY_BOUNDS=y
> CONFIG_UBSAN_BOUNDS=y
> CONFIG_UBSAN_ARRAY_BOUNDS=y
> CONFIG_UBSAN_SHIFT=y
> CONFIG_UBSAN_DIV_ZERO=y
> CONFIG_UBSAN_SIGNED_OVERFLOW=y
> CONFIG_UBSAN_UNSIGNED_OVERFLOW=y
> CONFIG_UBSAN_OBJECT_SIZE=y
> CONFIG_UBSAN_BOOL=y
> CONFIG_UBSAN_ENUM=y
> CONFIG_UBSAN_ALIGNMENT=y
> CONFIG_UBSAN_SANITIZE_ALL=y
> # CONFIG_TEST_UBSAN is not set
>
> and clang-10:
>
> lib/strncpy_from_user.o: warning: objtool: strncpy_from_user()+0x253: call to __ubsan_handle_add_overflow() with UACCESS enabled
> lib/strnlen_user.o: warning: objtool: strnlen_user()+0x244: call to __ubsan_handle_add_overflow() with UACCESS enabled
> ld: init/main.o: in function `kmalloc':
> /home/boris/kernel/linux/./include/linux/slab.h:557: undefined reference to `__ubsan_handle_alignment_assumption'
> ld: init/initramfs.o: in function `kmalloc':
> /home/boris/kernel/linux/./include/linux/slab.h:552: undefined reference to `__ubsan_handle_alignment_assumption'
> ld: init/initramfs.o: in function `kmalloc_large':
> /home/boris/kernel/linux/./include/linux/slab.h:481: undefined reference to `__ubsan_handle_alignment_assumption'
> ld: init/initramfs.o: in function `kmalloc':
> /home/boris/kernel/linux/./include/linux/slab.h:552: undefined reference to `__ubsan_handle_alignment_assumption'
> ld: /home/boris/kernel/linux/./include/linux/slab.h:552: undefined reference to `__ubsan_handle_alignment_assumption'
> ld: init/initramfs.o:/home/boris/kernel/linux/./include/linux/slab.h:552: more undefined references to `__ubsan_handle_alignment_assumption' follow
> ld: mm/mremap.o: in function `get_extent':
> /home/boris/kernel/linux/mm/mremap.c:355: undefined reference to `__compiletime_assert_327'

^ this one is https://lore.kernel.org/lkml/20201230154104.522605-1-arnd@kernel.org/.
Trying to get the last of these tracked down.  I think there were some
changes to UBSAN configs that weren't tested with clang before merged.

> ld: mm/rmap.o: in function `anon_vma_chain_alloc':
> /home/boris/kernel/linux/mm/rmap.c:136: undefined reference to `__ubsan_handle_alignment_assumption'
> ld: mm/rmap.o: in function `anon_vma_alloc':
> /home/boris/kernel/linux/mm/rmap.c:89: undefined reference to `__ubsan_handle_alignment_assumption'
> ld: mm/rmap.o: in function `anon_vma_chain_alloc':
> /home/boris/kernel/linux/mm/rmap.c:136: undefined reference to `__ubsan_handle_alignment_assumption'
> ld: /home/boris/kernel/linux/mm/rmap.c:136: undefined reference to `__ubsan_handle_alignment_assumption'
> ld: /home/boris/kernel/linux/mm/rmap.c:136: undefined reference to `__ubsan_handle_alignment_assumption'
> ld: mm/vmalloc.o:/home/boris/kernel/linux/mm/vmalloc.c:1213: more undefined references to `__ubsan_handle_alignment_assumption' follow
> make: *** [Makefile:1164: vmlinux] Error 1
>
> --
> Regards/Gruss,
>     Boris.
>
> https://people.kernel.org/tglx/notes-about-netiquette



-- 
Thanks,
~Nick Desaulniers