This is a note to let you know that I've just added the patch titled

kprobes/x86: Disable optimizing on the function jumps to indirect thunk

to the 4.14-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...

The filename of the patch is: kprobes-x86-disable-optimizing-on-the-function-jumps-to-indirect-thunk.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 stable@vger.kernel.org know about it.

From c86a32c09f8ced67971a2310e3b0dda4d1749007 Mon Sep 17 00:00:00 2001

From: Masami Hiramatsu mhiramat@kernel.org Date: Fri, 19 Jan 2018 01:15:20 +0900 Subject: kprobes/x86: Disable optimizing on the function jumps to indirect thunk

From: Masami Hiramatsu mhiramat@kernel.org

commit c86a32c09f8ced67971a2310e3b0dda4d1749007 upstream.

Since indirect jump instructions will be replaced by jump to __x86_indirect_thunk_*, those jmp instruction must be treated as an indirect jump. Since optprobe prohibits to optimize probes in the function which uses an indirect jump, it also needs to find out the function which jump to __x86_indirect_thunk_* and disable optimization.

Add a check that the jump target address is between the __indirect_thunk_start/end when optimizing kprobe.

Signed-off-by: Masami Hiramatsu mhiramat@kernel.org Signed-off-by: Thomas Gleixner tglx@linutronix.de Acked-by: David Woodhouse dwmw@amazon.co.uk Cc: Andi Kleen ak@linux.intel.com Cc: Peter Zijlstra peterz@infradead.org Cc: Ananth N Mavinakayanahalli ananth@linux.vnet.ibm.com Cc: Arjan van de Ven arjan@linux.intel.com Cc: Greg Kroah-Hartman gregkh@linux-foundation.org Link: https://lkml.kernel.org/r/151629212062.10241.6991266100233002273.stgit@devbo... Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org

--- arch/x86/kernel/kprobes/opt.c | 23 ++++++++++++++++++++++- 1 file changed, 22 insertions(+), 1 deletion(-)

--- a/arch/x86/kernel/kprobes/opt.c +++ b/arch/x86/kernel/kprobes/opt.c @@ -40,6 +40,7 @@ #include <asm/debugreg.h> #include <asm/set_memory.h> #include <asm/sections.h> +#include <asm/nospec-branch.h>

#include "common.h"

@@ -205,7 +206,7 @@ static int copy_optimized_instructions(u }

/* Check whether insn is indirect jump */ -static int insn_is_indirect_jump(struct insn *insn) +static int __insn_is_indirect_jump(struct insn *insn) { return ((insn->opcode.bytes[0] == 0xff && (X86_MODRM_REG(insn->modrm.value) & 6) == 4) || /* Jump */ @@ -239,6 +240,26 @@ static int insn_jump_into_range(struct i return (start <= target && target <= start + len); }

+static int insn_is_indirect_jump(struct insn *insn) +{ + int ret = __insn_is_indirect_jump(insn); + +#ifdef CONFIG_RETPOLINE + /* + * Jump to x86_indirect_thunk_* is treated as an indirect jump. + * Note that even with CONFIG_RETPOLINE=y, the kernel compiled with + * older gcc may use indirect jump. So we add this check instead of + * replace indirect-jump check. + */ + if (!ret) + ret = insn_jump_into_range(insn, + (unsigned long)__indirect_thunk_start, + (unsigned long)__indirect_thunk_end - + (unsigned long)__indirect_thunk_start); +#endif + return ret; +} + /* Decode whole function to ensure any instructions don't jump into target */ static int can_optimize(unsigned long paddr) {

Patches currently in stable-queue which might be from mhiramat@kernel.org are

queue-4.14/kprobes-x86-disable-optimizing-on-the-function-jumps-to-indirect-thunk.patch queue-4.14/kprobes-x86-blacklist-indirect-thunk-functions-for-kprobes.patch queue-4.14/retpoline-introduce-start-end-markers-of-indirect-thunk.patch