[PATCH] vmlinux.lds.h: Fix placement of '.data..decrypted' section

[PATCH] vmlinux.lds.h: Fix placement of '.data..decrypted' section

[Nathan Chancellor]

Commit d4c639990036 ("vmlinux.lds.h: Avoid orphan section with !SMP")
fixed an orphan section warning by adding the '.data..decrypted' section
to the linker script under the PERCPU_DECRYPTED_SECTION define but that
placement introduced a panic with !SMP, as the percpu sections are not
instantiated with that configuration so attempting to access variables
defined with DEFINE_PER_CPU_DECRYPTED() will result in a page fault.

Move the '.data..decrypted' section to the DATA_MAIN define so that the
variables in it are properly instantiated at boot time with
CONFIG_SMP=n.

Cc: stable@vger.kernel.org
Fixes: d4c639990036 ("vmlinux.lds.h: Avoid orphan section with !SMP")
Link: https://lore.kernel.org/cbbd3548-880c-d2ca-1b67-5bb93b291d5f@huawei.com/
Debugged-by: Ard Biesheuvel <ardb@kernel.org>
Reported-by: Zhao Wenhui <zhaowenhui8@huawei.com>
Tested-by: xiafukun <xiafukun@huawei.com>
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
---
 include/asm-generic/vmlinux.lds.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index d06ada2341cb..3dc5824141cd 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -347,6 +347,7 @@
 #define DATA_DATA							\
 	*(.xiptext)							\
 	*(DATA_MAIN)							\
+	*(.data..decrypted)						\
 	*(.ref.data)							\
 	*(.data..shared_aligned) /* percpu related */			\
 	MEM_KEEP(init.data*)						\
@@ -995,7 +996,6 @@
 #ifdef CONFIG_AMD_MEM_ENCRYPT
 #define PERCPU_DECRYPTED_SECTION					\
 	. = ALIGN(PAGE_SIZE);						\
-	*(.data..decrypted)						\
 	*(.data..percpu..decrypted)					\
 	. = ALIGN(PAGE_SIZE);
 #else

base-commit: f0c4d9fc9cc9462659728d168387191387e903cc
-- 
2.38.1

Re: [PATCH] vmlinux.lds.h: Fix placement of '.data..decrypted' section

[Kees Cook]

On Tue, 8 Nov 2022 10:49:34 -0700, Nathan Chancellor wrote:
> Commit d4c639990036 ("vmlinux.lds.h: Avoid orphan section with !SMP")
> fixed an orphan section warning by adding the '.data..decrypted' section
> to the linker script under the PERCPU_DECRYPTED_SECTION define but that
> placement introduced a panic with !SMP, as the percpu sections are not
> instantiated with that configuration so attempting to access variables
> defined with DEFINE_PER_CPU_DECRYPTED() will result in a page fault.
> 
> [...]

Applied to for-linus/hardening, thanks!

[1/1] vmlinux.lds.h: Fix placement of '.data..decrypted' section
      https://git.kernel.org/kees/c/000f8870a47b

-- 
Kees Cook