Don't leak NT bit into next task

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@suse.de>
[backport from Chuck Ebbert]
Signed-off-by: Chuck Ebbert <76306.1226@compuserve.com>
Signed-off-by: Chris Wright <chrisw@sous-sol.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/arch/x86_64/kernel/entry.S b/arch/x86_64/kernel/entry.S
index aa8d8939abc1692df22e7000c226095a44167678..28e88bf103ea63a9e86f4ec080107d193b0a8962 100644 (file)
--- a/arch/x86_64/kernel/entry.S
+++ b/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)

diff --git a/arch/x86_64/kernel/setup64.c b/arch/x86_64/kernel/setup64.c
index 417de564456e23baead28629aeeb2a218c8bee4b..845785e1a561d947cc4cb5440fb91c9b712f9f9d 100644 (file)
--- a/arch/x86_64/kernel/setup64.c
+++ b/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);
 }

diff --git a/include/asm-x86_64/system.h b/include/asm-x86_64/system.h
index 6bf170bceae1b4a7d114305c340240670698a032..bd376bc8c4ab26b5702bf667ad84f18f38fb5184 100644 (file)
--- a/include/asm-x86_64/system.h
+++ b/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 */       \