Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965944AbaLLGrK (ORCPT ); Fri, 12 Dec 2014 01:47:10 -0500 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:51777 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758839AbaLLGQy (ORCPT ); Fri, 12 Dec 2014 01:16:54 -0500 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit MIME-Version: 1.0 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org CC: akpm@linux-foundation.org, "Thomas Gleixner" , "Andy Lutomirski" , "Linus Torvalds" Date: Fri, 12 Dec 2014 06:14:25 +0000 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) Subject: [PATCH 3.2 151/164] x86_64, traps: Fix the espfix64 #DF fixup and rewrite it in C In-Reply-To: X-SA-Exim-Connect-IP: 2001:470:1f08:1539:c97:8151:cc89:c28d X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.2.65-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Andy Lutomirski commit af726f21ed8af2cdaa4e93098dc211521218ae65 upstream. There's nothing special enough about the espfix64 double fault fixup to justify writing it in assembly. Move it to C. This also fixes a bug: if the double fault came from an IST stack, the old asm code would return to a partially uninitialized stack frame. Fixes: 3891a04aafd668686239349ea58f3314ea2af86b Signed-off-by: Andy Lutomirski Reviewed-by: Thomas Gleixner Signed-off-by: Linus Torvalds [bwh: Backported to 3.2: - Keep using the paranoiderrorentry macro to generate the asm code - Adjust context] Signed-off-by: Ben Hutchings --- arch/x86/kernel/entry_64.S | 34 ++-------------------------------- arch/x86/kernel/traps.c | 24 ++++++++++++++++++++++++ 2 files changed, 26 insertions(+), 32 deletions(-) --- a/arch/x86/kernel/entry_64.S +++ b/arch/x86/kernel/entry_64.S @@ -873,6 +873,7 @@ ENTRY(native_iret) jnz native_irq_return_ldt #endif +.global native_irq_return_iret native_irq_return_iret: iretq @@ -972,37 +973,6 @@ ENTRY(retint_kernel) CFI_ENDPROC END(common_interrupt) - /* - * If IRET takes a fault on the espfix stack, then we - * end up promoting it to a doublefault. In that case, - * modify the stack to make it look like we just entered - * the #GP handler from user space, similar to bad_iret. - */ -#ifdef CONFIG_X86_ESPFIX64 - ALIGN -__do_double_fault: - XCPT_FRAME 1 RDI+8 - movq RSP(%rdi),%rax /* Trap on the espfix stack? */ - sarq $PGDIR_SHIFT,%rax - cmpl $ESPFIX_PGD_ENTRY,%eax - jne do_double_fault /* No, just deliver the fault */ - cmpl $__KERNEL_CS,CS(%rdi) - jne do_double_fault - movq RIP(%rdi),%rax - cmpq $native_irq_return_iret,%rax - jne do_double_fault /* This shouldn't happen... */ - movq PER_CPU_VAR(kernel_stack),%rax - subq $(6*8-KERNEL_STACK_OFFSET),%rax /* Reset to original stack */ - movq %rax,RSP(%rdi) - movq $0,(%rax) /* Missing (lost) #GP error code */ - movq $general_protection,RIP(%rdi) - retq - CFI_ENDPROC -END(__do_double_fault) -#else -# define __do_double_fault do_double_fault -#endif - /* * End of kprobes section */ @@ -1169,7 +1139,7 @@ zeroentry overflow do_overflow zeroentry bounds do_bounds zeroentry invalid_op do_invalid_op zeroentry device_not_available do_device_not_available -paranoiderrorentry double_fault __do_double_fault +paranoiderrorentry double_fault do_double_fault zeroentry coprocessor_segment_overrun do_coprocessor_segment_overrun errorentry invalid_TSS do_invalid_TSS errorentry segment_not_present do_segment_not_present --- a/arch/x86/kernel/traps.c +++ b/arch/x86/kernel/traps.c @@ -224,6 +224,30 @@ dotraplinkage void do_double_fault(struc static const char str[] = "double fault"; struct task_struct *tsk = current; +#ifdef CONFIG_X86_ESPFIX64 + extern unsigned char native_irq_return_iret[]; + + /* + * If IRET takes a non-IST fault on the espfix64 stack, then we + * end up promoting it to a doublefault. In that case, modify + * the stack to make it look like we just entered the #GP + * handler from user space, similar to bad_iret. + */ + if (((long)regs->sp >> PGDIR_SHIFT) == ESPFIX_PGD_ENTRY && + regs->cs == __KERNEL_CS && + regs->ip == (unsigned long)native_irq_return_iret) + { + struct pt_regs *normal_regs = task_pt_regs(current); + + /* Fake a #GP(0) from userspace. */ + memmove(&normal_regs->ip, (void *)regs->sp, 5*8); + normal_regs->orig_ax = 0; /* Missing (lost) #GP error code */ + regs->ip = (unsigned long)general_protection; + regs->sp = (unsigned long)&normal_regs->orig_ax; + return; + } +#endif + /* Return not checked because double check cannot be ignored */ notify_die(DIE_TRAP, str, regs, error_code, X86_TRAP_DF, SIGSEGV); -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/