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CC:     Masami Hiramatsu <mhiramat@kernel.org>,
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        Linus Torvalds <torvalds@linux-foundation.org>,
        Peter Zijlstra <peterz@infradead.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ye Xiaolong <xiaolong.ye@intel.com>,
        Ingo Molnar <mingo@kernel.org>,
        Sasha Levin <Alexander.Levin@microsoft.com>
Subject: [PATCH AUTOSEL for 4.9 159/219] kprobes/x86: Fix kprobe-booster not
 to boost far call instructions
Thread-Topic: [PATCH AUTOSEL for 4.9 159/219] kprobes/x86: Fix kprobe-booster
 not to boost far call instructions
Thread-Index: AQHTsz8YOzWhW0ipYEG1TtCvRM6enw==
Date:   Sat, 3 Mar 2018 22:29:29 +0000
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From: Masami Hiramatsu <mhiramat@kernel.org>

[ Upstream commit bd0b90676c30fe640e7ead919b3e38846ac88ab7 ]

Fix the kprobe-booster not to boost far call instruction,
because a call may store the address in the single-step
execution buffer to the stack, which should be modified
after single stepping.

Currently, this instruction will be filtered as not
boostable in resume_execution(), so this is not a
critical issue.

Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Ananth N Mavinakayanahalli <ananth@linux.vnet.ibm.com>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: David S . Miller <davem@davemloft.net>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ye Xiaolong <xiaolong.ye@intel.com>
Link: http://lkml.kernel.org/r/149076340615.22469.14066273186134229909.stgi=
t@devbox
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
---
 arch/x86/kernel/kprobes/core.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/x86/kernel/kprobes/core.c b/arch/x86/kernel/kprobes/core.=
c
index b55d07b9d530..808ee7f566f8 100644
--- a/arch/x86/kernel/kprobes/core.c
+++ b/arch/x86/kernel/kprobes/core.c
@@ -199,6 +199,8 @@ retry:
 		return (opcode !=3D 0x62 && opcode !=3D 0x67);
 	case 0x70:
 		return 0; /* can't boost conditional jump */
+	case 0x90:
+		return opcode !=3D 0x9a;	/* can't boost call far */
 	case 0xc0:
 		/* can't boost software-interruptions */
 		return (0xc1 < opcode && opcode < 0xcc) || opcode =3D=3D 0xcf;
--=20
2.14.1