linux-kernel - [PATCH 5.4 136/184] arm64/vdso: Discard .note.gnu.property sections in vDSO

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Message-Id: <20210510101954.611509007@linuxfoundation.org>
Date:   Mon, 10 May 2021 12:20:30 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Bill Wendling <morbo@...gle.com>,
        Kees Cook <keescook@...omium.org>,
        Ard Biesheuvel <ardb@...nel.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.4 136/184] arm64/vdso: Discard .note.gnu.property sections in vDSO

From: Bill Wendling <morbo@...gle.com>

[ Upstream commit 388708028e6937f3fc5fc19aeeb847f8970f489c ]

The arm64 assembler in binutils 2.32 and above generates a program
property note in a note section, .note.gnu.property, to encode used x86
ISAs and features. But the kernel linker script only contains a single
NOTE segment:

  PHDRS
  {
    text    PT_LOAD    FLAGS(5) FILEHDR PHDRS; /* PF_R|PF_X */
    dynamic PT_DYNAMIC FLAGS(4);               /* PF_R */
    note    PT_NOTE    FLAGS(4);               /* PF_R */
  }

The NOTE segment generated by the vDSO linker script is aligned to 4 bytes.
But the .note.gnu.property section must be aligned to 8 bytes on arm64.

  $ readelf -n vdso64.so

  Displaying notes found in: .note
    Owner                Data size      Description
    Linux                0x00000004     Unknown note type: (0x00000000)
     description data: 06 00 00 00
  readelf: Warning: note with invalid namesz and/or descsz found at offset 0x20
  readelf: Warning:  type: 0x78, namesize: 0x00000100, descsize: 0x756e694c, alignment: 8

Since the note.gnu.property section in the vDSO is not checked by the
dynamic linker, discard the .note.gnu.property sections in the vDSO.

Similar to commit 4caffe6a28d31 ("x86/vdso: Discard .note.gnu.property
sections in vDSO"), but for arm64.

Signed-off-by: Bill Wendling <morbo@...gle.com>
Reviewed-by: Kees Cook <keescook@...omium.org>
Acked-by: Ard Biesheuvel <ardb@...nel.org>
Link: https://lore.kernel.org/r/20210423205159.830854-1-morbo@google.com
Signed-off-by: Catalin Marinas <catalin.marinas@....com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 arch/arm64/kernel/vdso/vdso.lds.S | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/kernel/vdso/vdso.lds.S b/arch/arm64/kernel/vdso/vdso.lds.S
index 7ad2d3a0cd48..815df253f96e 100644
--- a/arch/arm64/kernel/vdso/vdso.lds.S
+++ b/arch/arm64/kernel/vdso/vdso.lds.S
@@ -28,6 +28,13 @@ SECTIONS
 	.gnu.version_d	: { *(.gnu.version_d) }
 	.gnu.version_r	: { *(.gnu.version_r) }
 
+	/*
+	 * Discard .note.gnu.property sections which are unused and have
+	 * different alignment requirement from vDSO note sections.
+	 */
+	/DISCARD/	: {
+		*(.note.GNU-stack .note.gnu.property)
+	}
 	.note		: { *(.note.*) }		:text	:note
 
 	. = ALIGN(16);
@@ -48,7 +55,6 @@ SECTIONS
 	PROVIDE(end = .);
 
 	/DISCARD/	: {
-		*(.note.GNU-stack)
 		*(.data .data.* .gnu.linkonce.d.* .sdata*)
 		*(.bss .sbss .dynbss .dynsbss)
 	}
-- 
2.30.2