This is a note to let you know that I've just added the patch titled
x86/mpx: Fix 32-bit address space calculation
to the 4.3-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
x86-mpx-fix-32-bit-address-space-calculation.patch
and it can be found in the queue-4.3 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.
>From f3119b830264d89d216bfb378ab65065dffa02d9 Mon Sep 17 00:00:00 2001
From: Dave Hansen <dave.han...@linux.intel.com>
Date: Wed, 11 Nov 2015 10:19:34 -0800
Subject: x86/mpx: Fix 32-bit address space calculation
From: Dave Hansen <dave.han...@linux.intel.com>
commit f3119b830264d89d216bfb378ab65065dffa02d9 upstream.
I received a bug report that running 32-bit MPX binaries on
64-bit kernels was broken. I traced it down to this little code
snippet. We were switching our "number of bounds directory
entries" calculation correctly. But, we didn't switch the other
side of the calculation: the virtual space size.
This meant that we were calculating an absurd size for
bd_entry_virt_space() on 32-bit because we used the 64-bit
virt_space.
This was _also_ broken for 32-bit kernels running on 64-bit
hardware since boot_cpu_data.x86_virt_bits=48 even when running
in 32-bit mode.
Correct that and properly handle all 3 possible cases:
1. 32-bit binary on 64-bit kernel
2. 64-bit binary on 64-bit kernel
3. 32-bit binary on 32-bit kernel
This manifested in having bounds tables not properly unmapped.
It "leaked" memory but had no functional impact otherwise.
Signed-off-by: Dave Hansen <dave.han...@linux.intel.com>
Cc: Andy Lutomirski <l...@amacapital.net>
Cc: Borislav Petkov <b...@alien8.de>
Cc: Brian Gerst <brge...@gmail.com>
Cc: Dave Hansen <d...@sr71.net>
Cc: Denys Vlasenko <dvlas...@redhat.com>
Cc: H. Peter Anvin <h...@zytor.com>
Cc: Linus Torvalds <torva...@linux-foundation.org>
Cc: Peter Zijlstra <pet...@infradead.org>
Cc: Thomas Gleixner <t...@linutronix.de>
Link: http://lkml.kernel.org/r/20151111181934.fa7fa...@viggo.jf.intel.com
Signed-off-by: Ingo Molnar <mi...@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>
---
arch/x86/mm/mpx.c | 22 +++++++++++++++++-----
1 file changed, 17 insertions(+), 5 deletions(-)
--- a/arch/x86/mm/mpx.c
+++ b/arch/x86/mm/mpx.c
@@ -722,11 +722,23 @@ static unsigned long mpx_get_bt_entry_of
*/
static inline unsigned long bd_entry_virt_space(struct mm_struct *mm)
{
- unsigned long long virt_space = (1ULL << boot_cpu_data.x86_virt_bits);
- if (is_64bit_mm(mm))
- return virt_space / MPX_BD_NR_ENTRIES_64;
- else
- return virt_space / MPX_BD_NR_ENTRIES_32;
+ unsigned long long virt_space;
+ unsigned long long GB = (1ULL << 30);
+
+ /*
+ * This covers 32-bit emulation as well as 32-bit kernels
+ * running on 64-bit harware.
+ */
+ if (!is_64bit_mm(mm))
+ return (4ULL * GB) / MPX_BD_NR_ENTRIES_32;
+
+ /*
+ * 'x86_virt_bits' returns what the hardware is capable
+ * of, and returns the full >32-bit adddress space when
+ * running 32-bit kernels on 64-bit hardware.
+ */
+ virt_space = (1ULL << boot_cpu_data.x86_virt_bits);
+ return virt_space / MPX_BD_NR_ENTRIES_64;
}
/*
Patches currently in stable-queue which might be from
dave.han...@linux.intel.com are
queue-4.3/x86-fpu-fix-get_xsave_addr-behavior-under-virtualization.patch
queue-4.3/x86-mpx-do-proper-get_user-when-running-32-bit-binaries-on-64-bit-kernels.patch
queue-4.3/x86-mpx-fix-32-bit-address-space-calculation.patch
queue-4.3/x86-fpu-fix-32-bit-signal-frame-handling.patch
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