lkml.org 
[lkml]   [2015]   [Dec]   [7]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH 4.3 051/125] x86/mpx: Fix 32-bit address space calculation
Date
4.3-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Dave Hansen <dave.hansen@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.hansen@linux.intel.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Dave Hansen <dave@sr71.net>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20151111181934.FA7FAC34@viggo.jf.intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@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;
}

/*



\
 
 \ /
  Last update: 2015-12-07 16:41    [W:0.271 / U:2.644 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site