From: Andy Lutomirski <luto@amacapital.net>
To: Stefani Seibold <stefani@seibold.net>, X86 ML <x86@kernel.org>,
"H. Peter Anvin" <hpa@zytor.com>
Cc: Greg KH <gregkh@linuxfoundation.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Andi Kleen <ak@linux.intel.com>,
Andrea Arcangeli <aarcange@redhat.com>,
John Stultz <john.stultz@linaro.org>,
Pavel Emelyanov <xemul@parallels.com>,
Cyrill Gorcunov <gorcunov@openvz.org>,
andriy.shevchenko@linux.intel.com,
Martin.Runge@rohde-schwarz.com, Andreas.Brief@rohde-schwarz.com,
Andy Lutomirski <luto@amacapital.net>
Subject: [PATCH v2 4/4] x86: Zero-pad the VVAR page
Date: Thu, 27 Feb 2014 16:18:15 -0800 [thread overview]
Message-ID: <3916f23d922cc8b9d683d9e0e53a5431ac0440dd.1393545985.git.luto@amacapital.net> (raw)
In-Reply-To: <cover.1393545985.git.luto@amacapital.net>
In-Reply-To: <cover.1393545985.git.luto@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: Andy Lutomirski <luto@amacapital.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);
--
1.8.5.3
next prev parent reply other threads:[~2014-02-28 0:18 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-02-26 19:34 Final: Add 32 bit VDSO time function support Stefani Seibold
2014-02-26 20:10 ` Andy Lutomirski
2014-02-26 20:45 ` Greg KH
2014-02-26 20:54 ` Andy Lutomirski
2014-02-27 0:55 ` Andy Lutomirski
2014-02-27 1:02 ` [PATCH 0/2] Improvements/fixes to 32-bit vdso timing Andy Lutomirski
2014-02-27 1:02 ` [PATCH 1/2] x86: Mark __vdso entries as asmlinkage Andy Lutomirski
2014-02-27 3:25 ` H. Peter Anvin
2014-02-27 3:39 ` Andi Kleen
2014-02-27 5:06 ` H. Peter Anvin
2014-02-27 5:19 ` Andy Lutomirski
2014-02-27 5:22 ` H. Peter Anvin
2014-02-27 20:11 ` Andy Lutomirski
2014-02-27 23:12 ` H. Peter Anvin
2014-02-27 5:07 ` H. Peter Anvin
2014-02-27 1:02 ` [PATCH 2/2] x86: Inline the CLOCK_MONOTONIC vdso code Andy Lutomirski
2014-02-28 0:18 ` [PATCH v2 0/4] vDSO fixes, on top of tip/x86/vdso Andy Lutomirski
2014-02-28 0:18 ` [PATCH v2 1/4] x86: Use the default ABI for the 32-bit vDSO Andy Lutomirski
2014-02-28 7:28 ` Stefani Seibold
2014-02-28 15:06 ` H. Peter Anvin
2014-02-28 20:19 ` Andy Lutomirski
2014-03-01 13:43 ` Stefani Seibold
2014-02-28 0:18 ` [PATCH v2 2/4] x86: Inline the CLOCK_MONOTONIC vdso code Andy Lutomirski
2014-02-28 0:18 ` [PATCH v2 3/4] x86: Patch alternatives in the 32-bit vDSO Andy Lutomirski
2014-02-28 7:22 ` Stefani Seibold
2014-03-01 14:04 ` Stefani Seibold
2014-02-28 0:18 ` Andy Lutomirski [this message]
2014-02-28 7:33 ` [PATCH v2 0/4] vDSO fixes, on top of tip/x86/vdso Stefani Seibold
2014-02-28 20:15 ` Andy Lutomirski
2014-03-01 14:02 ` Stefani Seibold
2014-02-28 7:22 ` Final: Add 32 bit VDSO time function support Stefani Seibold
2014-03-01 2:00 ` Andy Lutomirski
2014-03-01 22:56 ` H. Peter Anvin
2014-03-02 8:01 ` Stefani Seibold
2014-02-27 5:07 ` H. Peter Anvin
2014-02-27 12:14 ` Ingo Molnar
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