From 33db1fd48ac3d90385b412b41a8a6525096ac6d5 Mon Sep 17 00:00:00 2001 From: Denys Vlasenko Date: Tue, 17 Mar 2015 14:52:24 +0100 Subject: [PATCH] x86/asm/entry/64: Enable interrupts *after* we fetch PER_CPU_VAR(old_rsp) We want to use PER_CPU_VAR(old_rsp) as a simple temporary register, to shuffle user-space RSP into (and from) when we set up the system call stack frame. At that point we cannot shuffle values into general purpose registers, because we have not saved them yet. To be able to do this shuffling into a memory location, we must be atomic and must not be preempted while we do the shuffling, otherwise the 'temporary' register gets overwritten by some other task's temporary register contents ... Tested-by: Borislav Petkov Signed-off-by: Denys Vlasenko Acked-by: Borislav Petkov Cc: Alexei Starovoitov Cc: Andy Lutomirski Cc: Frederic Weisbecker Cc: H. Peter Anvin Cc: Kees Cook Cc: Linus Torvalds Cc: Oleg Nesterov Cc: Steven Rostedt Cc: Will Drewry Link: http://lkml.kernel.org/r/1426600344-8254-1-git-send-email-dvlasenk@redhat.com Signed-off-by: Ingo Molnar --- arch/x86/kernel/entry_64.S | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-) diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S index d86788c3257b..aed3f11c373b 100644 --- a/arch/x86/kernel/entry_64.S +++ b/arch/x86/kernel/entry_64.S @@ -241,16 +241,16 @@ GLOBAL(system_call_after_swapgs) movq %rsp,PER_CPU_VAR(old_rsp) /* kernel_stack is set so that 5 slots (iret frame) are preallocated */ movq PER_CPU_VAR(kernel_stack),%rsp - /* - * No need to follow this irqs off/on section - it's straight - * and short: - */ - ENABLE_INTERRUPTS(CLBR_NONE) ALLOC_PT_GPREGS_ON_STACK 8 /* +8: space for orig_ax */ movq %rcx,RIP(%rsp) movq PER_CPU_VAR(old_rsp),%rcx movq %r11,EFLAGS(%rsp) movq %rcx,RSP(%rsp) + /* + * No need to follow this irqs off/on section - it's straight + * and short: + */ + ENABLE_INTERRUPTS(CLBR_NONE) movq_cfi rax,ORIG_RAX SAVE_C_REGS_EXCEPT_RAX_RCX_R11 movq $-ENOSYS,RAX(%rsp) -- 2.20.1