[patch 03/18] Dont leak NT bit into next task

From: Greg KH
Date: Tue Feb 20 2007 - 20:51:56 EST


-stable review patch. If anyone has any objections, please let us know.

------------------
From: Andi Kleen <ak@xxxxxxx>

SYSENTER can cause a NT to be set which might cause crashes on the IRET
in the next task.

Following similar i386 patch from Linus.

Signed-off-by: Andi Kleen <ak@xxxxxxx>
[backport from Chuck Ebbert]
Signed-off-by: Chuck Ebbert <76306.1226@xxxxxxxxxxxxxx>
Signed-off-by: Chris Wright <chrisw@xxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxx>
---
arch/x86_64/kernel/entry.S | 4 ++++
arch/x86_64/kernel/setup64.c | 4 ++++
include/asm-x86_64/system.h | 5 +++--
3 files changed, 11 insertions(+), 2 deletions(-)

--- linux-2.6.18.7.orig/arch/x86_64/kernel/entry.S
+++ linux-2.6.18.7/arch/x86_64/kernel/entry.S
@@ -146,6 +146,10 @@
/* rdi: prev */
ENTRY(ret_from_fork)
CFI_DEFAULT_STACK
+ push kernel_eflags(%rip)
+ CFI_ADJUST_CFA_OFFSET 4
+ popf # reset kernel eflags
+ CFI_ADJUST_CFA_OFFSET -4
call schedule_tail
GET_THREAD_INFO(%rcx)
testl $(_TIF_SYSCALL_TRACE|_TIF_SYSCALL_AUDIT),threadinfo_flags(%rcx)
--- linux-2.6.18.7.orig/arch/x86_64/kernel/setup64.c
+++ linux-2.6.18.7/arch/x86_64/kernel/setup64.c
@@ -178,6 +178,8 @@ void __cpuinit check_efer(void)
}
}

+unsigned long kernel_eflags;
+
/*
* cpu_init() initializes state that is per-CPU. Some data is already
* initialized (naturally) in the bootstrap process, such as the GDT
@@ -290,4 +292,6 @@ void __cpuinit cpu_init (void)
set_debugreg(0UL, 7);

fpu_init();
+
+ raw_local_save_flags(kernel_eflags);
}
--- linux-2.6.18.7.orig/include/asm-x86_64/system.h
+++ linux-2.6.18.7/include/asm-x86_64/system.h
@@ -14,12 +14,13 @@
#define __RESTORE(reg,offset) "movq (14-" #offset ")*8(%%rsp),%%" #reg "\n\t"

/* frame pointer must be last for get_wchan */
-#define SAVE_CONTEXT "pushq %%rbp ; movq %%rsi,%%rbp\n\t"
-#define RESTORE_CONTEXT "movq %%rbp,%%rsi ; popq %%rbp\n\t"
+#define SAVE_CONTEXT "pushf ; pushq %%rbp ; movq %%rsi,%%rbp\n\t"
+#define RESTORE_CONTEXT "movq %%rbp,%%rsi ; popq %%rbp ; popf\t"

#define __EXTRA_CLOBBER \
,"rcx","rbx","rdx","r8","r9","r10","r11","r12","r13","r14","r15"

+/* Save restore flags to clear handle leaking NT */
#define switch_to(prev,next,last) \
asm volatile(SAVE_CONTEXT \
"movq %%rsp,%P[threadrsp](%[prev])\n\t" /* save RSP */ \

--
-
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