Patch "kprobes/x86: Disable optimizing on the function jumps to indirect thunk" has been added to the 4.4-stable tree

[<gregkh@linuxfoundation.org>]

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 4.4-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:
     kprobes-x86-disable-optimizing-on-the-function-jumps-to-indirect-thunk.patch
and it can be found in the queue-4.4 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@devbox
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
@@ -36,6 +36,7 @@
 #include <asm/alternative.h>
 #include <asm/insn.h>
 #include <asm/debugreg.h>
+#include <asm/nospec-branch.h>
 
 #include "common.h"
 
@@ -191,7 +192,7 @@ 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 */
@@ -225,6 +226,26 @@ 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-4.4/kprobes-x86-disable-optimizing-on-the-function-jumps-to-indirect-thunk.patch
queue-4.4/kprobes-x86-blacklist-indirect-thunk-functions-for-kprobes.patch
queue-4.4/retpoline-introduce-start-end-markers-of-indirect-thunk.patch