Commit
5b11f1cee5 ("x86, boot: straighten out ranges to copy/zero in
compressed/head*.S")
introduced a separate .pgtable section, splitting it out from the rest
of .bss. This section was added without the writeable flag, marking it
as read-only. This results in the linker putting the .rela.dyn section
(containing bogus dynamic relocations from head_64.o) after the .bss and
.pgtable sections.
When objcopy is used to convert compressed/vmlinux into a binary for
the bzImage:
$ objcopy -O binary -R .note -R .comment -S arch/x86/boot/compressed/vmlinux \
arch/x86/boot/vmlinux.bin
the .bss and .pgtable sections get materialized as ~176KiB of zero
bytes in the binary in order to place .rela.dyn at the correct location.
Fix this by marking .pgtable as writeable. This moves the .rela.dyn
section up in the ELF image layout so that .bss and .pgtable are the
last allocated sections and so don't appear in bzImage.
[ bp: Massage commit message. ]
Signed-off-by: Arvind Sankar <nivedita@alum.mit.edu>
Signed-off-by: Borislav Petkov <bp@suse.de>
Acked-by: Kees Cook <keescook@chromium.org>
Link: https://lkml.kernel.org/r/20200109150218.16544-1-nivedita@alum.mit.edu
3ee372ccce