From: Masami Hiramatsu <mhiramat@kernel.org>
To: Ingo Molnar <mingo@kernel.org>, Steven Rostedt <rostedt@goodmis.org>
Cc: "Naveen N . Rao" <naveen.n.rao@linux.vnet.ibm.com>,
Ananth N Mavinakayanahalli <ananth@linux.ibm.com>,
linux-kernel@vger.kernel.org, mhiramat@kernel.org,
x86@kernel.org
Subject: [BUGFIX PATCH -tip 1/2] x86/kprobes: Retrieve correct opcode for group instruction
Date: Thu, 25 Feb 2021 21:02:08 +0900 [thread overview]
Message-ID: <161425452807.93763.16971315111567129320.stgit@devnote2> (raw)
In-Reply-To: <161425451732.93763.18329509061375062554.stgit@devnote2>
Since the opcodes start from 0xff are group5 instruction group which is
not 2 bytes opcode but the extended opcode determined by the MOD/RM byte.
The commit abd82e533d88 ("x86/kprobes: Do not decode opcode in resume_execution()")
used insn->opcode.bytes[1], but that is not correct. We have to refer
the insn->modrm.bytes[1] instead.
Fixes: abd82e533d88 ("x86/kprobes: Do not decode opcode in resume_execution()")
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
---
arch/x86/kernel/kprobes/core.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)
diff --git a/arch/x86/kernel/kprobes/core.c b/arch/x86/kernel/kprobes/core.c
index df776cdca327..08674e7a5d7b 100644
--- a/arch/x86/kernel/kprobes/core.c
+++ b/arch/x86/kernel/kprobes/core.c
@@ -448,7 +448,11 @@ static void set_resume_flags(struct kprobe *p, struct insn *insn)
break;
#endif
case 0xff:
- opcode = insn->opcode.bytes[1];
+ /*
+ * Since the 0xff is an extended group opcode, the instruction
+ * is determined by the MOD/RM byte.
+ */
+ opcode = insn->modrm.bytes[0];
if ((opcode & 0x30) == 0x10) {
/*
* call absolute, indirect
next prev parent reply other threads:[~2021-02-25 12:03 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-25 12:01 [BUGFIX PATCH -tip 0/2] x86/kprobes: Fix bugs in resume execution code Masami Hiramatsu
2021-02-25 12:02 ` Masami Hiramatsu [this message]
2021-02-25 12:02 ` [BUGFIX PATCH -tip 2/2] x86/kprobes: Identify far indirect JMP correctly Masami Hiramatsu
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