From 309944be296efbb3ca4737d12ef49d2ba97cbecc Mon Sep 17 00:00:00 2001 From: Andy Lutomirski Date: Mon, 17 Mar 2014 23:22:11 +0100 Subject: x86, vdso: Zero-pad the VVAR page 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 Link: http://lkml.kernel.org/r/1395094933-14252-12-git-send-email-stefani@seibold.net Signed-off-by: H. Peter Anvin 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); -- cgit v0.10.2