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Patch "x86/ldt: Correct FPU emulation access to LDT" has been added to the 4.1-stable tree

PATCH [email protected] 1 participant 1 message Sep 15, 2015

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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 <[email protected]> know about it.

Quoted 1 line

From 4809146b86c3d41ce588fdb767d021e2a80600dd Mon Sep 17 00:00:00 2001

From: Juergen Gross <[email protected]>
Date: Thu, 6 Aug 2015 19:54:34 +0200
Subject: x86/ldt: Correct FPU emulation access to LDT

From: Juergen Gross <[email protected]>

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 <[email protected]>
Reviewed-by Andy Lutomirski <[email protected]>
Cc Linus Torvalds <[email protected]>
Cc Peter Zijlstra <[email protected]>
Cc Thomas Gleixner <[email protected]>
Cc [email protected]
Link http://lkml.kernel.org/r/[email protected] open here
Signed-off-by Ingo Molnar <[email protected]>
Signed-off-by Greg Kroah-Hartman <[email protected]>
---
 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(-)
arch/x86/math-emu/fpu_entry.c +1 -2
@@ -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 */
arch/x86/math-emu/fpu_system.h +18 -3
@@ -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(&current->mm->context.lock);
+	if (current->mm->context.ldt && seg < current->mm->context.ldt->size)
+		ret = current->mm->context.ldt->entries[seg];
+	mutex_unlock(&current->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)
arch/x86/math-emu/get_address.c +1 -2
@@ -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 [email protected] 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