From: Masami Hiramatsu mhiramat@kernel.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@kernel.org Signed-off-by: Peter Zijlstra (Intel) peterz@infradead.org Cc: Juergen Gross jgross@suse.com Cc: x86@kernel.org Cc: Boris Ostrovsky boris.ostrovsky@oracle.com Cc: Ingo Molnar mingo@kernel.org Cc: Stefano Stabellini sstabellini@kernel.org Cc: Andrew Cooper andrew.cooper3@citrix.com Cc: Borislav Petkov bp@alien8.de Cc: xen-devel@lists.xenproject.org Cc: Randy Dunlap rdunlap@infradead.org Cc: Josh Poimboeuf jpoimboe@redhat.com Link: https://lkml.kernel.org/r/156777566048.25081.6296162369492175325.stgit@devno... Signed-off-by: Maximilian Heyne mheyne@amazon.de Cc: stable@vger.kernel.org # 5.4.x --- arch/x86/kernel/kprobes/core.c | 4 ++++ 1 file changed, 4 insertions(+)

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;