[PATCH 4.9 050/240] arm64/vdso: Discard .note.gnu.property sections in vDSO

Greg Kroah-Hartman
2021-05-20T11:05:55Z

From: Bill Wendling <morbo@google.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@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Acked-by: Ard Biesheuvel <ardb@kernel.org>
Link: https://lore.kernel.org/r/20210423205159.830854-1-morbo@google.com
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Sasha Levin <sashal@kernel.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 beca249bc2f3..b3e6c4d5b75c 100644
--- a/arch/arm64/kernel/vdso/vdso.lds.S
+++ b/arch/arm64/kernel/vdso/vdso.lds.S
@@ -39,6 +39,13 @@ 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);
@@ -59,7 +66,6 @@ SECTIONS
PROVIDE(end = .);

/DISCARD/ : {
- *(.note.GNU-stack)
*(.data .data.* .gnu.linkonce.d.* .sdata*)
*(.bss .sbss .dynbss .dynsbss)
}
--
2.30.2