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Date: Wed, 16 Dec 2015 09:37:28 -0800
From: Kamal Mostafa <kamal@...onical.com>
To: linux-kernel@...r.kernel.org, stable@...r.kernel.org,
kernel-team@...ts.ubuntu.com
Cc: Dave Hansen <dave.hansen@...ux.intel.com>,
Andrew Morton <akpm@...ux-foundation.org>,
Dave Hansen <dave@...1.net>, "H. Peter Anvin" <hpa@...or.com>,
Linus Torvalds <torvalds@...ux-foundation.org>,
Peter Zijlstra <peterz@...radead.org>,
Ingo Molnar <mingo@...nel.org>,
Kamal Mostafa <kamal@...onical.com>
Subject: [PATCH 3.19.y-ckt 008/128] x86/mpx: Introduce new 'directory entry' to 'addr' helper function
3.19.8-ckt12 -stable review patch. If anyone has any objections, please let me know.
------------------
From: Dave Hansen <dave.hansen@...ux.intel.com>
commit 54587653904c552c56b9dec153d7a89063394b09 upstream.
Currently, to get from a bounds directory entry to the virtual
address of a bounds table, we simply mask off a few low bits.
However, the set of bits we mask off is different for 32-bit and
64-bit binaries.
This breaks the operation out in to a helper function and also
adds a temporary variable to store the result until we are
sure we are returning one.
Signed-off-by: Dave Hansen <dave.hansen@...ux.intel.com>
Reviewed-by: Thomas Gleixner <tglx@...utronix.de>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Dave Hansen <dave@...1.net>
Cc: H. Peter Anvin <hpa@...or.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Link: http://lkml.kernel.org/r/20150607183704.007686CE@viggo.jf.intel.com
Signed-off-by: Ingo Molnar <mingo@...nel.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@...onical.com>
---
arch/x86/include/asm/mpx.h | 1 -
arch/x86/mm/mpx.c | 41 ++++++++++++++++++++++++++++++++++-------
2 files changed, 34 insertions(+), 8 deletions(-)
diff --git a/arch/x86/include/asm/mpx.h b/arch/x86/include/asm/mpx.h
index a952a13d..2857144 100644
--- a/arch/x86/include/asm/mpx.h
+++ b/arch/x86/include/asm/mpx.h
@@ -46,7 +46,6 @@
#define MPX_BNDCFG_TAIL 12
#define MPX_BNDSTA_ADDR_MASK (~((1UL<<MPX_BNDSTA_TAIL)-1))
#define MPX_BNDCFG_ADDR_MASK (~((1UL<<MPX_BNDCFG_TAIL)-1))
-#define MPX_BT_ADDR_MASK (~((1UL<<MPX_BD_ENTRY_TAIL)-1))
#define MPX_BNDCFG_ADDR_MASK (~((1UL<<MPX_BNDCFG_TAIL)-1))
#define MPX_BNDSTA_ERROR_CODE 0x3
diff --git a/arch/x86/mm/mpx.c b/arch/x86/mm/mpx.c
index 9c208e4..1013f04 100644
--- a/arch/x86/mm/mpx.c
+++ b/arch/x86/mm/mpx.c
@@ -555,29 +555,55 @@ static int mpx_resolve_fault(long __user *addr, int write)
return 0;
}
+static unsigned long mpx_bd_entry_to_bt_addr(struct mm_struct *mm,
+ unsigned long bd_entry)
+{
+ unsigned long bt_addr = bd_entry;
+ int align_to_bytes;
+ /*
+ * Bit 0 in a bt_entry is always the valid bit.
+ */
+ bt_addr &= ~MPX_BD_ENTRY_VALID_FLAG;
+ /*
+ * Tables are naturally aligned at 8-byte boundaries
+ * on 64-bit and 4-byte boundaries on 32-bit. The
+ * documentation makes it appear that the low bits
+ * are ignored by the hardware, so we do the same.
+ */
+ if (is_64bit_mm(mm))
+ align_to_bytes = 8;
+ else
+ align_to_bytes = 4;
+ bt_addr &= ~(align_to_bytes-1);
+ return bt_addr;
+}
+
/*
* Get the base of bounds tables pointed by specific bounds
* directory entry.
*/
static int get_bt_addr(struct mm_struct *mm,
- long __user *bd_entry, unsigned long *bt_addr)
+ long __user *bd_entry_ptr,
+ unsigned long *bt_addr_result)
{
int ret;
int valid_bit;
+ unsigned long bd_entry;
+ unsigned long bt_addr;
- if (!access_ok(VERIFY_READ, (bd_entry), sizeof(*bd_entry)))
+ if (!access_ok(VERIFY_READ, (bd_entry_ptr), sizeof(*bd_entry_ptr)))
return -EFAULT;
while (1) {
int need_write = 0;
pagefault_disable();
- ret = get_user(*bt_addr, bd_entry);
+ ret = get_user(bd_entry, bd_entry_ptr);
pagefault_enable();
if (!ret)
break;
if (ret == -EFAULT)
- ret = mpx_resolve_fault(bd_entry, need_write);
+ ret = mpx_resolve_fault(bd_entry_ptr, need_write);
/*
* If we could not resolve the fault, consider it
* userspace's fault and error out.
@@ -586,8 +612,8 @@ static int get_bt_addr(struct mm_struct *mm,
return ret;
}
- valid_bit = *bt_addr & MPX_BD_ENTRY_VALID_FLAG;
- *bt_addr &= MPX_BT_ADDR_MASK;
+ valid_bit = bd_entry & MPX_BD_ENTRY_VALID_FLAG;
+ bt_addr = mpx_bd_entry_to_bt_addr(mm, bd_entry);
/*
* When the kernel is managing bounds tables, a bounds directory
@@ -596,7 +622,7 @@ static int get_bt_addr(struct mm_struct *mm,
* data in the address field, we know something is wrong. This
* -EINVAL return will cause a SIGSEGV.
*/
- if (!valid_bit && *bt_addr)
+ if (!valid_bit && bt_addr)
return -EINVAL;
/*
* Do we have an completely zeroed bt entry? That is OK. It
@@ -607,6 +633,7 @@ static int get_bt_addr(struct mm_struct *mm,
if (!valid_bit)
return -ENOENT;
+ *bt_addr_result = bt_addr;
return 0;
}
--
1.9.1
--
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