Re: Patch "vmlinux.lds.h: Handle clang's module.{c,d}tor sections" has been added to the 5.13-stable tree

Re: Patch "vmlinux.lds.h: Handle clang's module.{c,d}tor sections" has been added to the 5.13-stable tree

[Nathan Chancellor]

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Hi Greg,

On Sun, Aug 15, 2021 at 02:54:26PM +0200, gregkh@linuxfoundation.org wrote:
> 
> This is a note to let you know that I've just added the patch titled
> 
>     vmlinux.lds.h: Handle clang's module.{c,d}tor sections
> 
> to the 5.13-stable tree which can be found at:
>     http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
> 
> The filename of the patch is:
>      vmlinux.lds.h-handle-clang-s-module.-c-d-tor-sections.patch
> and it can be found in the queue-5.13 subdirectory.

Attached are backports for 4.4 to 5.10. I am not sure if anyone is
actually using KASAN with clang on 4.4 (ChromeOS maybe?) but it does not
hurt to have it just in case.

I did not get any emails that the patch failed to apply on the older
versions, I assume this is because I did just a "Cc: stable@vger.kernel.org"
without any version or fixes tag. Is there any "official" way to notate
that I want a particular patch applied to all supported kernel versions
aside from adding "# v4.4+" to the Cc tag so that I can provide manual
backports for those versions?

Cheers,
Nathan

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From fd073a15e9941b70d0db84d28d539cf3535e1b59 Mon Sep 17 00:00:00 2001
From: Nathan Chancellor <nathan@kernel.org>
Date: Fri, 30 Jul 2021 19:31:08 -0700
Subject: [PATCH 4.4 to 4.14] vmlinux.lds.h: Handle clang's module.{c,d}tor
 sections

commit 848378812e40152abe9b9baf58ce2004f76fb988 upstream.

A recent change in LLVM causes module_{c,d}tor sections to appear when
CONFIG_K{A,C}SAN are enabled, which results in orphan section warnings
because these are not handled anywhere:

ld.lld: warning: arch/x86/pci/built-in.a(legacy.o):(.text.asan.module_ctor) is being placed in '.text.asan.module_ctor'
ld.lld: warning: arch/x86/pci/built-in.a(legacy.o):(.text.asan.module_dtor) is being placed in '.text.asan.module_dtor'
ld.lld: warning: arch/x86/pci/built-in.a(legacy.o):(.text.tsan.module_ctor) is being placed in '.text.tsan.module_ctor'

Fangrui explains: "the function asan.module_ctor has the SHF_GNU_RETAIN
flag, so it is in a separate section even with -fno-function-sections
(default)".

Place them in the TEXT_TEXT section so that these technologies continue
to work with the newer compiler versions. All of the KASAN and KCSAN
KUnit tests continue to pass after this change.

Cc: stable@vger.kernel.org
Link: https://github.com/ClangBuiltLinux/linux/issues/1432
Link: https://github.com/llvm/llvm-project/commit/7b789562244ee941b7bf2cefeb3fc08a59a01865
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Reviewed-by: Fangrui Song <maskray@google.com>
Acked-by: Marco Elver <elver@google.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20210731023107.1932981-1-nathan@kernel.org
[nc: Fix conflicts due to lack of cf68fffb66d60 and 266ff2a8f51f0]
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
---
 include/asm-generic/vmlinux.lds.h | 1 +
 1 file changed, 1 insertion(+)

diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index c9790b2cdf34..45fe7295051f 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -465,6 +465,7 @@
 		*(.text.unknown .text.unknown.*)			\
 		*(.text..refcount)					\
 		*(.ref.text)						\
+		*(.text.asan.* .text.tsan.*)				\
 	MEM_KEEP(init.text)						\
 	MEM_KEEP(exit.text)						\
 

base-commit: 162b95d01320370b80cb2d5724cea4ae538ac740
-- 
2.33.0.rc2


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From 07154ab1ed7ce98f9418421152753e1bc8029829 Mon Sep 17 00:00:00 2001
From: Nathan Chancellor <nathan@kernel.org>
Date: Fri, 30 Jul 2021 19:31:08 -0700
Subject: [PATCH 4.19 to 5.10] vmlinux.lds.h: Handle clang's module.{c,d}tor
 sections

commit 848378812e40152abe9b9baf58ce2004f76fb988 upstream.

A recent change in LLVM causes module_{c,d}tor sections to appear when
CONFIG_K{A,C}SAN are enabled, which results in orphan section warnings
because these are not handled anywhere:

ld.lld: warning: arch/x86/pci/built-in.a(legacy.o):(.text.asan.module_ctor) is being placed in '.text.asan.module_ctor'
ld.lld: warning: arch/x86/pci/built-in.a(legacy.o):(.text.asan.module_dtor) is being placed in '.text.asan.module_dtor'
ld.lld: warning: arch/x86/pci/built-in.a(legacy.o):(.text.tsan.module_ctor) is being placed in '.text.tsan.module_ctor'

Fangrui explains: "the function asan.module_ctor has the SHF_GNU_RETAIN
flag, so it is in a separate section even with -fno-function-sections
(default)".

Place them in the TEXT_TEXT section so that these technologies continue
to work with the newer compiler versions. All of the KASAN and KCSAN
KUnit tests continue to pass after this change.

Cc: stable@vger.kernel.org
Link: https://github.com/ClangBuiltLinux/linux/issues/1432
Link: https://github.com/llvm/llvm-project/commit/7b789562244ee941b7bf2cefeb3fc08a59a01865
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Reviewed-by: Fangrui Song <maskray@google.com>
Acked-by: Marco Elver <elver@google.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20210731023107.1932981-1-nathan@kernel.org
[nc: Resolve conflict due to lack of cf68fffb66d60]
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
---
 include/asm-generic/vmlinux.lds.h | 1 +
 1 file changed, 1 insertion(+)

diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index 18468b46c450..a774361f28d4 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -599,6 +599,7 @@
 		NOINSTR_TEXT						\
 		*(.text..refcount)					\
 		*(.ref.text)						\
+		*(.text.asan.* .text.tsan.*)				\
 	MEM_KEEP(init.text*)						\
 	MEM_KEEP(exit.text*)						\
 

base-commit: 5805e5eec901e830c7741d4916270d0b9cfd6743
-- 
2.33.0.rc2

Re: Patch "vmlinux.lds.h: Handle clang's module.{c,d}tor sections" has been added to the 5.13-stable tree

[Greg KH]

On Sun, Aug 15, 2021 at 03:54:39PM -0700, Nathan Chancellor wrote:
> Hi Greg,
> 
> On Sun, Aug 15, 2021 at 02:54:26PM +0200, gregkh@linuxfoundation.org wrote:
> > 
> > This is a note to let you know that I've just added the patch titled
> > 
> >     vmlinux.lds.h: Handle clang's module.{c,d}tor sections
> > 
> > to the 5.13-stable tree which can be found at:
> >     http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
> > 
> > The filename of the patch is:
> >      vmlinux.lds.h-handle-clang-s-module.-c-d-tor-sections.patch
> > and it can be found in the queue-5.13 subdirectory.
> 
> Attached are backports for 4.4 to 5.10. I am not sure if anyone is
> actually using KASAN with clang on 4.4 (ChromeOS maybe?) but it does not
> hurt to have it just in case.
> 
> I did not get any emails that the patch failed to apply on the older
> versions, I assume this is because I did just a "Cc: stable@vger.kernel.org"
> without any version or fixes tag. Is there any "official" way to notate
> that I want a particular patch applied to all supported kernel versions
> aside from adding "# v4.4+" to the Cc tag so that I can provide manual
> backports for those versions?

That comment is exactly how you should ask for that, otherwise I do a
"best effort" type of backport and just stop when it does not apply.

Or you can provide a "Fixes:" tag, which will show me exactly how far
back to apply patches, and that usually works better as it will catch
commits that get backported to older kernels.

thanks,

greg k-h