linux-kernel - [PATCH 5.4 13/18] x86: kprobes: Prohibit probing on instruction which has emulate prefix

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Date:   Fri, 13 May 2022 16:23:39 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Masami Hiramatsu <mhiramat@...nel.org>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        Juergen Gross <jgross@...e.com>, x86@...nel.org,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Ingo Molnar <mingo@...nel.org>,
        Stefano Stabellini <sstabellini@...nel.org>,
        Andrew Cooper <andrew.cooper3@...rix.com>,
        Borislav Petkov <bp@...en8.de>, xen-devel@...ts.xenproject.org,
        Randy Dunlap <rdunlap@...radead.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Maximilian Heyne <mheyne@...zon.de>
Subject: [PATCH 5.4 13/18] x86: kprobes: Prohibit probing on instruction which has emulate prefix

From: Masami Hiramatsu <mhiramat@...nel.org>

commit 004e8dce9c5595697951f7cd0e9f66b35c92265e upstream.

Prohibit probing on instruction which has XEN_EMULATE_PREFIX
or KVM's emulate prefix. Since that prefix is a marker for Xen
and KVM, if we modify the marker by kprobe's int3, that doesn't
work as expected.

Signed-off-by: Masami Hiramatsu <mhiramat@...nel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Cc: Juergen Gross <jgross@...e.com>
Cc: x86@...nel.org
Cc: Boris Ostrovsky <boris.ostrovsky@...cle.com>
Cc: Ingo Molnar <mingo@...nel.org>
Cc: Stefano Stabellini <sstabellini@...nel.org>
Cc: Andrew Cooper <andrew.cooper3@...rix.com>
Cc: Borislav Petkov <bp@...en8.de>
Cc: xen-devel@...ts.xenproject.org
Cc: Randy Dunlap <rdunlap@...radead.org>
Cc: Josh Poimboeuf <jpoimboe@...hat.com>
Link: https://lkml.kernel.org/r/156777566048.25081.6296162369492175325.stgit@devnote2
Signed-off-by: Maximilian Heyne <mheyne@...zon.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 arch/x86/kernel/kprobes/core.c |    4 ++++
 1 file changed, 4 insertions(+)

--- a/arch/x86/kernel/kprobes/core.c
+++ b/arch/x86/kernel/kprobes/core.c
@@ -358,6 +358,10 @@ int __copy_instruction(u8 *dest, u8 *src
 	kernel_insn_init(insn, dest, MAX_INSN_SIZE);
 	insn_get_length(insn);
 
+	/* We can not probe force emulate prefixed instruction */
+	if (insn_has_emulate_prefix(insn))
+		return 0;
+
 	/* Another subsystem puts a breakpoint, failed to recover */
 	if (insn->opcode.bytes[0] == BREAKPOINT_INSTRUCTION)
 		return 0;