From: Andy Lutomirski <l...@amacapital.net>
By coincidence, the VVAR page is at the end of an ELF segment. As a
result, if it ends up being a partial page, the kernel loader will
leave garbage behind at the end of the vvar page. Zero-pad it to a
full page to fix this issue.
This has probably been broken since the VVAR page was introduced.
On QEMU, if you dump the run-time contents of the VVAR page, you can
find entertaining strings from seabios left behind.
It's remotely possible that this is a security bug -- conceivably
there's some BIOS out there that leaves something sensitive in the
few K of memory that is exposed to userspace.
Signed-off-by: Stefani Seibold <stef...@seibold.net>
---
arch/x86/kernel/vmlinux.lds.S | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/arch/x86/kernel/vmlinux.lds.S b/arch/x86/kernel/vmlinux.lds.S
index 1d4897b..49edf2d 100644
--- a/arch/x86/kernel/vmlinux.lds.S
+++ b/arch/x86/kernel/vmlinux.lds.S
@@ -164,6 +164,11 @@ SECTIONS
#undef __VVAR_KERNEL_LDS
#undef EMIT_VVAR
+ /*
+ * Pad the rest of the page with zeros. Otherwise the loader
+ * can leave garbage here.
+ */
+ . = __vvar_beginning_hack + PAGE_SIZE;
} :data
. = ALIGN(__vvar_page + PAGE_SIZE, PAGE_SIZE);
--
1.9.0
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