[PATCH 3.19.y-ckt 006/128] x86/mpx: Add temporary variable to reduce masking
Kamal Mostafa
kamal at canonical.com
Wed Dec 16 17:37:26 UTC 2015
3.19.8-ckt12 -stable review patch. If anyone has any objections, please let me know.
------------------
From: Dave Hansen <dave.hansen at linux.intel.com>
commit a1149fc83a1f97612e72ec24a0bdbabff7b85e77 upstream.
When we allocate a bounds table, we call mmap(), then add a
"valid" bit to the value before storing it in to the bounds
directory.
If we fail along the way, we go and mask that valid bit
_back_ out. That seems a little silly, and this makes it
much more clear when we have a plain address versus an
actual table _entry_.
Signed-off-by: Dave Hansen <dave.hansen at linux.intel.com>
Reviewed-by: Thomas Gleixner <tglx at linutronix.de>
Cc: Andrew Morton <akpm at linux-foundation.org>
Cc: Dave Hansen <dave at sr71.net>
Cc: H. Peter Anvin <hpa at zytor.com>
Cc: Linus Torvalds <torvalds at linux-foundation.org>
Cc: Peter Zijlstra <peterz at infradead.org>
Link: http://lkml.kernel.org/r/20150607183704.3D69D5F4@viggo.jf.intel.com
Signed-off-by: Ingo Molnar <mingo at kernel.org>
[ kamal: 3.19-stable prereq for "46561c3 x86/mpx: Do proper get_user() when
running 32-bit binaries on 64-bit kernels" ]
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
arch/x86/mm/mpx.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)
diff --git a/arch/x86/mm/mpx.c b/arch/x86/mm/mpx.c
index 4d1c11c..9c208e4 100644
--- a/arch/x86/mm/mpx.c
+++ b/arch/x86/mm/mpx.c
@@ -409,6 +409,7 @@ static int allocate_bt(long __user *bd_entry)
unsigned long expected_old_val = 0;
unsigned long actual_old_val = 0;
unsigned long bt_addr;
+ unsigned long bd_new_entry;
int ret = 0;
/*
@@ -421,7 +422,7 @@ static int allocate_bt(long __user *bd_entry)
/*
* Set the valid flag (kinda like _PAGE_PRESENT in a pte)
*/
- bt_addr = bt_addr | MPX_BD_ENTRY_VALID_FLAG;
+ bd_new_entry = bt_addr | MPX_BD_ENTRY_VALID_FLAG;
/*
* Go poke the address of the new bounds table in to the
@@ -435,7 +436,7 @@ static int allocate_bt(long __user *bd_entry)
* of the MPX code that have to pagefault_disable().
*/
ret = user_atomic_cmpxchg_inatomic(&actual_old_val, bd_entry,
- expected_old_val, bt_addr);
+ expected_old_val, bd_new_entry);
if (ret)
goto out_unmap;
@@ -465,7 +466,7 @@ static int allocate_bt(long __user *bd_entry)
}
return 0;
out_unmap:
- vm_munmap(bt_addr & MPX_BT_ADDR_MASK, MPX_BT_SIZE_BYTES);
+ vm_munmap(bt_addr, MPX_BT_SIZE_BYTES);
return ret;
}
--
1.9.1
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