This is a note to let you know that I've just added the patch titled
x86/ldt: Correct FPU emulation access to LDT
to the 4.1-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-ldt-correct-fpu-emulation-access-to-ldt.patch
and it can be found in the queue-4.1 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 4809146b86c3d41ce588fdb767d021e2a80600dd Mon Sep 17 00:00:00 2001
From: Juergen Gross <jgross@xxxxxxxx>
Date: Thu, 6 Aug 2015 19:54:34 +0200
Subject: x86/ldt: Correct FPU emulation access to LDT
From: Juergen Gross <jgross@xxxxxxxx>
commit 4809146b86c3d41ce588fdb767d021e2a80600dd upstream.
Commit 37868fe113ff ("x86/ldt: Make modify_ldt synchronous")
introduced a new struct ldt_struct anchored at mm->context.ldt.
Adapt the x86 fpu emulation code to use that new structure.
Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
Reviewed-by: Andy Lutomirski <luto@xxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: billm@xxxxxxxxxxxxx
Link: http://lkml.kernel.org/r/1438883674-1240-1-git-send-email-jgross@xxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/x86/math-emu/fpu_entry.c | 3 +--
arch/x86/math-emu/fpu_system.h | 21 ++++++++++++++++++---
arch/x86/math-emu/get_address.c | 3 +--
3 files changed, 20 insertions(+), 7 deletions(-)
--- a/arch/x86/math-emu/fpu_entry.c
+++ b/arch/x86/math-emu/fpu_entry.c
@@ -29,7 +29,6 @@
#include <asm/uaccess.h>
#include <asm/traps.h>
-#include <asm/desc.h>
#include <asm/user.h>
#include <asm/i387.h>
@@ -185,7 +184,7 @@ void math_emulate(struct math_emu_info *
math_abort(FPU_info, SIGILL);
}
- code_descriptor = LDT_DESCRIPTOR(FPU_CS);
+ code_descriptor = FPU_get_ldt_descriptor(FPU_CS);
if (SEG_D_SIZE(code_descriptor)) {
/* The above test may be wrong, the book is not clear */
/* Segmented 32 bit protected mode */
--- a/arch/x86/math-emu/fpu_system.h
+++ b/arch/x86/math-emu/fpu_system.h
@@ -16,9 +16,24 @@
#include <linux/kernel.h>
#include <linux/mm.h>
-/* s is always from a cpu register, and the cpu does bounds checking
- * during register load --> no further bounds checks needed */
-#define LDT_DESCRIPTOR(s) (((struct desc_struct *)current->mm->context.ldt)[(s) >> 3])
+#include <asm/desc.h>
+#include <asm/mmu_context.h>
+
+static inline struct desc_struct FPU_get_ldt_descriptor(unsigned seg)
+{
+ static struct desc_struct zero_desc;
+ struct desc_struct ret = zero_desc;
+
+#ifdef CONFIG_MODIFY_LDT_SYSCALL
+ seg >>= 3;
+ mutex_lock(¤t->mm->context.lock);
+ if (current->mm->context.ldt && seg < current->mm->context.ldt->size)
+ ret = current->mm->context.ldt->entries[seg];
+ mutex_unlock(¤t->mm->context.lock);
+#endif
+ return ret;
+}
+
#define SEG_D_SIZE(x) ((x).b & (3 << 21))
#define SEG_G_BIT(x) ((x).b & (1 << 23))
#define SEG_GRANULARITY(x) (((x).b & (1 << 23)) ? 4096 : 1)
--- a/arch/x86/math-emu/get_address.c
+++ b/arch/x86/math-emu/get_address.c
@@ -20,7 +20,6 @@
#include <linux/stddef.h>
#include <asm/uaccess.h>
-#include <asm/desc.h>
#include "fpu_system.h"
#include "exception.h"
@@ -158,7 +157,7 @@ static long pm_address(u_char FPU_modrm,
addr->selector = PM_REG_(segment);
}
- descriptor = LDT_DESCRIPTOR(PM_REG_(segment));
+ descriptor = FPU_get_ldt_descriptor(segment);
base_address = SEG_BASE_ADDR(descriptor);
address = base_address + offset;
limit = base_address
Patches currently in stable-queue which might be from jgross@xxxxxxxx are
queue-4.1/x86-ldt-correct-ldt-access-in-single-stepping-logic.patch
queue-4.1/x86-ldt-correct-fpu-emulation-access-to-ldt.patch
queue-4.1/x86-ldt-further-fix-fpu-emulation.patch
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