kprobes/x86: Don't try to resolve kprobe faults from userspace

amluto · Ingo Molnar · commit 0cdd192cf40f · 2014-07-16T14:16:32.000+02:00
This commit: commit 6f6343f Author: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Date: Thu Apr 17 17:17:33 2014 +0900 kprobes/x86: Call exception handlers directly from do_int3/do_debug appears to have inadvertently dropped a check that the int3 came from kernel mode. Trying to dereference addr when addr is user-controlled is completely bogus. Signed-off-by: Andy Lutomirski <luto@amacapital.net> Acked-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Link: http://lkml.kernel.org/r/c4e339882c121aa76254f2adde3fcbdf502faec2.1405099506.git.luto@amacapital.net Signed-off-by: Ingo Molnar <mingo@kernel.org>
diff --git a/arch/x86/kernel/kprobes/core.c b/arch/x86/kernel/kprobes/core.c
@@ -574,6 +574,9 @@ int kprobe_int3_handler(struct pt_regs *regs)
 	struct kprobe *p;
 	struct kprobe_ctlblk *kcb;
 
+	if (user_mode_vm(regs))
+		return 0;
+
 	addr = (kprobe_opcode_t *)(regs->ip - sizeof(kprobe_opcode_t));
 	/*
 	 * We don't want to be preempted for the entire
