[PATCH] 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>
diff --git a/arch/x86_64/kernel/entry.S b/arch/x86_64/kernel/entry.S
index 4cbc652..2802524 100644
--- a/arch/x86_64/kernel/entry.S
+++ b/arch/x86_64/kernel/entry.S
@@ -155,6 +155,10 @@
/* 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 9332d23..8c4b80f 100644
--- a/arch/x86_64/kernel/setup64.c
+++ b/arch/x86_64/kernel/setup64.c
@@ -180,6 +180,8 @@
}
}
+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
@@ -281,4 +283,6 @@
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 6bf170b..bd376bc 100644
--- 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 */ \