From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linuxfoundation.org ([140.211.169.12]:58842 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755199AbdLUQvv (ORCPT ); Thu, 21 Dec 2017 11:51:51 -0500 Subject: Patch "x86/espfix/64: Stop assuming that pt_regs is on the entry stack" has been added to the 4.14-stable tree To: luto@kernel.org, David.Laight@aculab.com, boris.ostrovsky@oracle.com, bp@alien8.de, bp@suse.de, bpetkov@suse.de, brgerst@gmail.com, dave.hansen@intel.com, dave.hansen@linux.intel.com, dvlasenk@redhat.com, eduval@amazon.com, gregkh@linuxfoundation.org, hpa@zytor.com, jgross@suse.com, jpoimboe@redhat.com, mingo@kernel.org, peterz@infradead.org, riel@redhat.com, tglx@linutronix.de, torvalds@linux-foundation.org, will.deacon@arm.com Cc: , From: Date: Thu, 21 Dec 2017 17:05:58 +0100 Message-ID: <1513872358159192@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org List-ID: This is a note to let you know that I've just added the patch titled x86/espfix/64: Stop assuming that pt_regs is on the entry stack to the 4.14-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: x86-espfix-64-stop-assuming-that-pt_regs-is-on-the-entry-stack.patch and it can be found in the queue-4.14 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let know about it. >>From 6d9256f0a89eaff97fca6006100bcaea8d1d8bdb Mon Sep 17 00:00:00 2001 From: Andy Lutomirski Date: Mon, 4 Dec 2017 15:07:22 +0100 Subject: x86/espfix/64: Stop assuming that pt_regs is on the entry stack From: Andy Lutomirski commit 6d9256f0a89eaff97fca6006100bcaea8d1d8bdb upstream. When we start using an entry trampoline, a #GP from userspace will be delivered on the entry stack, not on the task stack. Fix the espfix64 #DF fixup to set up #GP according to TSS.SP0, rather than assuming that pt_regs + 1 == SP0. This won't change anything without an entry stack, but it will make the code continue to work when an entry stack is added. While we're at it, improve the comments to explain what's actually going on. Signed-off-by: Andy Lutomirski Signed-off-by: Thomas Gleixner Reviewed-by: Thomas Gleixner Reviewed-by: Borislav Petkov Cc: Boris Ostrovsky Cc: Borislav Petkov Cc: Borislav Petkov Cc: Brian Gerst Cc: Dave Hansen Cc: Dave Hansen Cc: David Laight Cc: Denys Vlasenko Cc: Eduardo Valentin Cc: Greg KH Cc: H. Peter Anvin Cc: Josh Poimboeuf Cc: Juergen Gross Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Rik van Riel Cc: Will Deacon Cc: aliguori@amazon.com Cc: daniel.gruss@iaik.tugraz.at Cc: hughd@google.com Cc: keescook@google.com Link: https://lkml.kernel.org/r/20171204150606.130778051@linutronix.de Signed-off-by: Ingo Molnar Signed-off-by: Greg Kroah-Hartman --- arch/x86/kernel/traps.c | 37 ++++++++++++++++++++++++++++--------- 1 file changed, 28 insertions(+), 9 deletions(-) --- a/arch/x86/kernel/traps.c +++ b/arch/x86/kernel/traps.c @@ -348,9 +348,15 @@ dotraplinkage void do_double_fault(struc /* * 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. + * end up promoting it to a doublefault. In that case, take + * advantage of the fact that we're not using the normal (TSS.sp0) + * stack right now. We can write a fake #GP(0) frame at TSS.sp0 + * and then modify our own IRET frame so that, when we return, + * we land directly at the #GP(0) vector with the stack already + * set up according to its expectations. + * + * The net result is that our #GP handler will think that we + * entered from usermode with the bad user context. * * No need for ist_enter here because we don't use RCU. */ @@ -358,13 +364,26 @@ dotraplinkage void do_double_fault(struc regs->cs == __KERNEL_CS && regs->ip == (unsigned long)native_irq_return_iret) { - struct pt_regs *normal_regs = task_pt_regs(current); + struct pt_regs *gpregs = (struct pt_regs *)this_cpu_read(cpu_tss.x86_tss.sp0) - 1; - /* 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->sp points to the failing IRET frame on the + * ESPFIX64 stack. Copy it to the entry stack. This fills + * in gpregs->ss through gpregs->ip. + * + */ + memmove(&gpregs->ip, (void *)regs->sp, 5*8); + gpregs->orig_ax = 0; /* Missing (lost) #GP error code */ + + /* + * Adjust our frame so that we return straight to the #GP + * vector with the expected RSP value. This is safe because + * we won't enable interupts or schedule before we invoke + * general_protection, so nothing will clobber the stack + * frame we just set up. + */ regs->ip = (unsigned long)general_protection; - regs->sp = (unsigned long)&normal_regs->orig_ax; + regs->sp = (unsigned long)&gpregs->orig_ax; return; } @@ -389,7 +408,7 @@ dotraplinkage void do_double_fault(struc * * Processors update CR2 whenever a page fault is detected. If a * second page fault occurs while an earlier page fault is being - * deliv- ered, the faulting linear address of the second fault will + * delivered, the faulting linear address of the second fault will * overwrite the contents of CR2 (replacing the previous * address). These updates to CR2 occur even if the page fault * results in a double fault or occurs during the delivery of a Patches currently in stable-queue which might be from luto@kernel.org are queue-4.14/x86-entry-64-simplify-reg-restore-code-in-the-standard-iret-paths.patch queue-4.14/x86-cpufeatures-fix-various-details-in-the-feature-definitions.patch queue-4.14/x86-entry-64-move-the-ist-stacks-into-struct-cpu_entry_area.patch queue-4.14/x86-dumpstack-add-get_stack_info-support-for-the-sysenter-stack.patch queue-4.14/x86-asm-don-t-use-the-confusing-.ifeq-directive.patch queue-4.14/selftests-x86-ldt_gdt-add-infrastructure-to-test-set_thread_area.patch queue-4.14/x86-entry-remap-the-tss-into-the-cpu-entry-area.patch queue-4.14/x86-entry-64-paravirt-use-paravirt-safe-macro-to-access-eflags.patch queue-4.14/x86-mm-fixmap-generalize-the-gdt-fixmap-mechanism-introduce-struct-cpu_entry_area.patch queue-4.14/x86-paravirt-dont-patch-flush_tlb_single.patch queue-4.14/x86-dumpstack-handle-stack-overflow-on-all-stacks.patch queue-4.14/x86-entry-64-use-pop-instead-of-movq-in-syscall_return_via_sysret.patch queue-4.14/x86-entry-64-return-to-userspace-from-the-trampoline-stack.patch queue-4.14/x86-paravirt-provide-a-way-to-check-for-hypervisors.patch queue-4.14/xen-x86-entry-64-add-xen-nmi-trap-entry.patch queue-4.14/x86-entry-64-remove-the-restore_c_regs_and_iret-label.patch queue-4.14/x86-entry-64-create-a-per-cpu-syscall-entry-trampoline.patch queue-4.14/x86-entry-64-remove-the-restore_..._regs-infrastructure.patch queue-4.14/x86-xen-64-x86-entry-64-clean-up-sp-code-in-cpu_initialize_context.patch queue-4.14/x86-entry-add-task_top_of_stack-to-find-the-top-of-a-task-s-stack.patch queue-4.14/x86-entry-64-remove-all-remaining-direct-thread_struct-sp0-reads.patch queue-4.14/x86-boot-relocate-definition-of-the-initial-state-of-cr0.patch queue-4.14/x86-entry-64-stop-initializing-tss.sp0-at-boot.patch queue-4.14/x86-entry-64-de-xen-ify-our-nmi-code.patch queue-4.14/objtool-don-t-report-end-of-section-error-after-an-empty-unwind-hint.patch queue-4.14/x86-entry-64-pass-sp0-directly-to-load_sp0.patch queue-4.14/x86-entry-64-use-a-per-cpu-trampoline-stack-for-idt-entries.patch queue-4.14/x86-entry-64-move-swapgs-into-the-common-iret-to-usermode-path.patch queue-4.14/x86-entry-64-shorten-test-instructions.patch queue-4.14/x86-cpufeature-add-user-mode-instruction-prevention-definitions.patch queue-4.14/x86-cpufeatures-make-cpu-bugs-sticky.patch queue-4.14/x86-espfix-64-stop-assuming-that-pt_regs-is-on-the-entry-stack.patch queue-4.14/x86-traps-use-a-new-on_thread_stack-helper-to-clean-up-an-assertion.patch queue-4.14/x86-xen-fix-xen-head-elf-annotations.patch queue-4.14/x86-entry-64-remove-thread_struct-sp0.patch queue-4.14/x86-entry-move-sysenter_stack-to-the-beginning-of-struct-tss_struct.patch queue-4.14/x86-entry-64-allocate-and-enable-the-sysenter-stack.patch queue-4.14/x86-unwinder-orc-dont-bail-on-stack-overflow.patch queue-4.14/x86-head-fix-head-elf-function-annotations.patch queue-4.14/selftests-x86-ldt_gdt-run-most-existing-ldt-test-cases-against-the-gdt-as-well.patch queue-4.14/x86-entry-32-pull-the-msr_ia32_sysenter_cs-update-code-out-of-native_load_sp0.patch queue-4.14/x86-entry-64-split-the-iret-to-user-and-iret-to-kernel-paths.patch queue-4.14/x86-entry-64-shrink-paranoid_exit_restore-and-make-labels-local.patch queue-4.14/x86-head-add-unwind-hint-annotations.patch queue-4.14/x86-head-remove-unused-bad_address-code.patch queue-4.14/x86-xen-add-unwind-hint-annotations.patch queue-4.14/x86-kasan-64-teach-kasan-about-the-cpu_entry_area.patch queue-4.14/x86-head-remove-confusing-comment.patch queue-4.14/x86-entry-64-remove-the-sysenter-stack-canary.patch queue-4.14/x86-mm-kasan-don-t-use-vmemmap_populate-to-initialize-shadow.patch queue-4.14/x86-entry-gdt-put-per-cpu-gdt-remaps-in-ascending-order.patch queue-4.14/x86-entry-fix-assumptions-that-the-hw-tss-is-at-the-beginning-of-cpu_tss.patch queue-4.14/x86-cpufeatures-re-tabulate-the-x86_feature-definitions.patch queue-4.14/x86-entry-32-fix-cpu_current_top_of_stack-initialization-at-boot.patch queue-4.14/ptrace-x86-make-user_64bit_mode-available-to-32-bit-builds.patch queue-4.14/x86-entry-64-make-cpu_entry_area.tss-read-only.patch queue-4.14/x86-mm-relocate-page-fault-error-codes-to-traps.h.patch queue-4.14/x86-unwinder-handle-stack-overflows-more-gracefully.patch queue-4.14/x86-entry-64-use-pop-instead-of-mov-to-restore-regs-on-nmi-return.patch queue-4.14/x86-irq-64-print-the-offending-ip-in-the-stack-overflow-warning.patch queue-4.14/x86-entry-clean-up-the-sysenter_stack-code.patch queue-4.14/x86-entry-64-merge-the-fast-and-slow-sysret-paths.patch queue-4.14/x86-entry-64-separate-cpu_current_top_of_stack-from-tss.sp0.patch queue-4.14/x86-boot-annotate-verify_cpu-as-a-callable-function.patch queue-4.14/x86-irq-remove-an-old-outdated-comment-about-context-tracking-races.patch