2022-11-08 18:13:35

by Nathan Chancellor

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

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: [email protected]
Fixes: d4c639990036 ("vmlinux.lds.h: Avoid orphan section with !SMP")
Link: https://lore.kernel.org/[email protected]/
Debugged-by: Ard Biesheuvel <[email protected]>
Reported-by: Zhao Wenhui <[email protected]>
Tested-by: xiafukun <[email protected]>
Signed-off-by: Nathan Chancellor <[email protected]>
---
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

2022-11-08 18:13:49

by Kees Cook

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

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