linux-kernel - [PATCH v2 0/2] arm: Warn on orphan section placement

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Message-Id: <20200622204915.2987555-1-keescook@chromium.org>
Date:   Mon, 22 Jun 2020 13:49:13 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Russell King <linux@...linux.org.uk>
Cc:     Kees Cook <keescook@...omium.org>,
        Masahiro Yamada <masahiroy@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Nathan Chancellor <natechancellor@...il.com>,
        Will Deacon <will@...nel.org>,
        Ard Biesheuvel <ardb@...nel.org>,
        Arnd Bergmann <arnd@...db.de>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: [PATCH v2 0/2] arm: Warn on orphan section placement

v2:
- split by architecture, rebase to v5.8-rc2
v1: https://lore.kernel.org/lkml/20200228002244.15240-1-keescook@chromium.org/

A recent bug[1] was solved for builds linked with ld.lld, and tracking
it down took way longer than it needed to (a year). Ultimately, it
boiled down to differences between ld.bfd and ld.lld's handling of
orphan sections. Similarly, the recent FGKASLR series brough up orphan
section handling too[2]. In both cases, it would have been nice if the
linker was running with --orphan-handling=warn so that surprise sections
wouldn't silently get mapped into the kernel image at locations up to the
whim of the linker's orphan handling logic. Instead, all desired sections
should be explicitly identified in the linker script (to be either kept or
discarded) with any orphans throwing a warning. The powerpc architecture
actually already does this, so this series extends coverage to arm.

This series needs one additional commit that is not yet in
any tree, but I hope to have it landed via x86 -tip shortly:
https://lore.kernel.org/lkml/20200228002244.15240-3-keescook@chromium.org/

Thanks!

-Kees

[1] https://github.com/ClangBuiltLinux/linux/issues/282
[2] https://lore.kernel.org/lkml/202002242122.AA4D1B8@keescook/

Kees Cook (2):
  arm/build: Warn on orphan section placement
  arm/boot: Warn on orphan section placement

 arch/arm/Makefile                             |  4 ++++
 arch/arm/boot/compressed/Makefile             |  2 ++
 arch/arm/boot/compressed/vmlinux.lds.S        | 17 ++++++--------
 .../arm/{kernel => include/asm}/vmlinux.lds.h | 22 ++++++++++++++-----
 arch/arm/kernel/vmlinux-xip.lds.S             |  5 ++---
 arch/arm/kernel/vmlinux.lds.S                 |  5 ++---
 6 files changed, 34 insertions(+), 21 deletions(-)
 rename arch/arm/{kernel => include/asm}/vmlinux.lds.h (92%)

-- 
2.25.1