arm64/vdso: Discard .note.gnu.property sections in vDSO

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>

diff --git a/arch/arm64/kernel/vdso/vdso.lds.S b/arch/arm64/kernel/vdso/vdso.lds.S
index 61dbb4c838ef75291aa983f75af1a0dde1eb3794..a5e61e09ea927e3020f73e92f96d70c1b90591a2 100644 (file)
--- a/arch/arm64/kernel/vdso/vdso.lds.S
+++ b/arch/arm64/kernel/vdso/vdso.lds.S
@@ -31,6 +31,13 @@ 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)
                *(.eh_frame .eh_frame_hdr)