[4/4] x86: kprobes: Prohibit probing on instruction which has emulate prefix

Commit Message

Maximilian Heyne May 10, 2022, 1:30 p.m. UTC

From: Masami Hiramatsu <[e-mail]>

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 <[e-mail]>
Signed-off-by: Peter Zijlstra (Intel) <[e-mail]>
Cc: Juergen Gross <[e-mail]>
Cc: [e-mail]
Cc: Boris Ostrovsky <[e-mail]>
Cc: Ingo Molnar <[e-mail]>
Cc: Stefano Stabellini <[e-mail]>
Cc: Andrew Cooper <[e-mail]>
Cc: Borislav Petkov <[e-mail]>
Cc: [e-mail]
Cc: Randy Dunlap <[e-mail]>
Cc: Josh Poimboeuf <[e-mail]>
Link: https://lkml.kernel.org/r/156777566048.25081.6296162369492175325.stgit@devnote2
Signed-off-by: Maximilian Heyne <[e-mail]>
Cc: [e-mail] # 5.4.x
---
 arch/x86/kernel/kprobes/core.c | 4 ++++
 1 file changed, 4 insertions(+)

Patch

diff --git a/arch/x86/kernel/kprobes/core.c b/arch/x86/kernel/kprobes/core.c
index c205d77d57da..3700dc94847c 100644
--- 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, u8 *real, struct insn *insn)
 	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;