This is a note to let you know that I've just added the patch titled x86/retpoline/entry: Convert entry assembler indirect jumps to the 4.9-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-retpoline-entry-convert-entry-assembler-indirect-jumps.patch and it can be found in the queue-4.9 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From 2641f08bb7fc63a636a2b18173221d7040a3512e Mon Sep 17 00:00:00 2001 From: David Woodhouse <dwmw@xxxxxxxxxxxx> Date: Thu, 11 Jan 2018 21:46:28 +0000 Subject: x86/retpoline/entry: Convert entry assembler indirect jumps From: David Woodhouse <dwmw@xxxxxxxxxxxx> commit 2641f08bb7fc63a636a2b18173221d7040a3512e upstream. Convert indirect jumps in core 32/64bit entry assembler code to use non-speculative sequences when CONFIG_RETPOLINE is enabled. Don't use CALL_NOSPEC in entry_SYSCALL_64_fastpath because the return address after the 'call' instruction must be *precisely* at the .Lentry_SYSCALL_64_after_fastpath label for stub_ptregs_64 to work, and the use of alternatives will mess that up unless we play horrid games to prepend with NOPs and make the variants the same length. It's not worth it; in the case where we ALTERNATIVE out the retpoline, the first instruction at __x86.indirect_thunk.rax is going to be a bare jmp *%rax anyway. Signed-off-by: David Woodhouse <dwmw@xxxxxxxxxxxx> Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Acked-by: Ingo Molnar <mingo@xxxxxxxxxx> Acked-by: Arjan van de Ven <arjan@xxxxxxxxxxxxxxx> Cc: gnomes@xxxxxxxxxxxxxxxxxxx Cc: Rik van Riel <riel@xxxxxxxxxx> Cc: Andi Kleen <ak@xxxxxxxxxxxxxxx> Cc: Josh Poimboeuf <jpoimboe@xxxxxxxxxx> Cc: thomas.lendacky@xxxxxxx Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx> Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> Cc: Jiri Kosina <jikos@xxxxxxxxxx> Cc: Andy Lutomirski <luto@xxxxxxxxxxxxxx> Cc: Dave Hansen <dave.hansen@xxxxxxxxx> Cc: Kees Cook <keescook@xxxxxxxxxx> Cc: Tim Chen <tim.c.chen@xxxxxxxxxxxxxxx> Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxxx> Cc: Paul Turner <pjt@xxxxxxxxxx> Link: https://lkml.kernel.org/r/1515707194-20531-7-git-send-email-dwmw@xxxxxxxxxxxx Signed-off-by: David Woodhouse <dwmw@xxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- arch/x86/entry/entry_32.S | 5 +++-- arch/x86/entry/entry_64.S | 10 ++++++++-- 2 files changed, 11 insertions(+), 4 deletions(-) --- a/arch/x86/entry/entry_32.S +++ b/arch/x86/entry/entry_32.S @@ -45,6 +45,7 @@ #include <asm/asm.h> #include <asm/smap.h> #include <asm/export.h> +#include <asm/nospec-branch.h> .section .entry.text, "ax" @@ -260,7 +261,7 @@ ENTRY(ret_from_fork) /* kernel thread */ 1: movl %edi, %eax - call *%ebx + CALL_NOSPEC %ebx /* * A kernel thread is allowed to return here after successfully * calling do_execve(). Exit to userspace to complete the execve() @@ -1062,7 +1063,7 @@ error_code: movl %ecx, %es TRACE_IRQS_OFF movl %esp, %eax # pt_regs pointer - call *%edi + CALL_NOSPEC %edi jmp ret_from_exception END(page_fault) --- a/arch/x86/entry/entry_64.S +++ b/arch/x86/entry/entry_64.S @@ -37,6 +37,7 @@ #include <asm/pgtable_types.h> #include <asm/export.h> #include <asm/kaiser.h> +#include <asm/nospec-branch.h> #include <linux/err.h> /* Avoid __ASSEMBLER__'ifying <linux/audit.h> just for this. */ @@ -208,7 +209,12 @@ entry_SYSCALL_64_fastpath: * It might end up jumping to the slow path. If it jumps, RAX * and all argument registers are clobbered. */ +#ifdef CONFIG_RETPOLINE + movq sys_call_table(, %rax, 8), %rax + call __x86_indirect_thunk_rax +#else call *sys_call_table(, %rax, 8) +#endif .Lentry_SYSCALL_64_after_fastpath_call: movq %rax, RAX(%rsp) @@ -380,7 +386,7 @@ ENTRY(stub_ptregs_64) jmp entry_SYSCALL64_slow_path 1: - jmp *%rax /* Called from C */ + JMP_NOSPEC %rax /* Called from C */ END(stub_ptregs_64) .macro ptregs_stub func @@ -457,7 +463,7 @@ ENTRY(ret_from_fork) 1: /* kernel thread */ movq %r12, %rdi - call *%rbx + CALL_NOSPEC %rbx /* * A kernel thread is allowed to return here after successfully * calling do_execve(). Exit to userspace to complete the execve() Patches currently in stable-queue which might be from dwmw@xxxxxxxxxxxx are queue-4.9/x86-spectre-add-boot-time-option-to-select-spectre-v2-mitigation.patch queue-4.9/x86-retpoline-irq32-convert-assembler-indirect-jumps.patch queue-4.9/objtool-detect-jumps-to-retpoline-thunks.patch queue-4.9/x86-cpufeatures-add-x86_bug_spectre_v.patch queue-4.9/x86-alternatives-add-missing-n-at-end-of-alternative-inline-asm.patch queue-4.9/x86-retpoline-hyperv-convert-assembler-indirect-jumps.patch queue-4.9/x86-retpoline-entry-convert-entry-assembler-indirect-jumps.patch queue-4.9/sysfs-cpu-fix-typos-in-vulnerability-documentation.patch queue-4.9/x86-cpufeatures-add-x86_bug_cpu_insecure.patch queue-4.9/x86-cpufeatures-make-cpu-bugs-sticky.patch queue-4.9/x86-cpu-amd-make-lfence-a-serializing-instruction.patch queue-4.9/x86-retpoline-ftrace-convert-ftrace-assembler-indirect-jumps.patch queue-4.9/objtool-allow-alternatives-to-be-ignored.patch queue-4.9/x86-cpu-implement-cpu-vulnerabilites-sysfs-functions.patch queue-4.9/x86-retpoline-crypto-convert-crypto-assembler-indirect-jumps.patch queue-4.9/x86-cpu-factor-out-application-of-forced-cpu-caps.patch queue-4.9/x86-retpoline-xen-convert-xen-hypercall-indirect-jumps.patch queue-4.9/x86-retpoline-checksum32-convert-assembler-indirect-jumps.patch queue-4.9/x86-mm-32-move-setup_clear_cpu_cap-x86_feature_pcid-earlier.patch queue-4.9/sysfs-cpu-add-vulnerability-folder.patch queue-4.9/x86-retpoline-fill-return-stack-buffer-on-vmexit.patch queue-4.9/x86-pti-rename-bug_cpu_insecure-to-bug_cpu_meltdown.patch queue-4.9/x86-retpoline-remove-compile-time-warning.patch queue-4.9/x86-alternatives-fix-optimize_nops-checking.patch queue-4.9/x86-cpu-amd-use-lfence_rdtsc-in-preference-to-mfence_rdtsc.patch queue-4.9/x86-retpoline-add-initial-retpoline-support.patch