Commit a980c0ef authored Aug 28, 2018 by Jann Horn Committed by Thomas Gleixner Sep 03, 2018

x86/kprobes: Refactor kprobes_fault() like kprobe_exceptions_notify()



This is an extension of commit b506a9d0 ("x86: code clarification patch
to Kprobes arch code"). As that commit explains, even though
kprobe_running() can't be called with preemption enabled, preemption does
not need to be disabled. If preemption is enabled, then this can't be
originate from a kprobe.

Also, use X86_TRAP_PF instead of 14.

Signed-off-by: Jann Horn <jannh@google.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Kees Cook <keescook@chromium.org>
Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: kernel-hardening@lists.openwall.com
Cc: dvyukov@google.com
Cc: "Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com>
Cc: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: linux-fsdevel@vger.kernel.org
Cc: Borislav Petkov <bp@alien8.de>
Link: https://lkml.kernel.org/r/20180828201421.157735-2-jannh@google.com

parent 60c1f892

arch/x86/mm/fault.c

+13 −11

Original line number	Diff line number	Diff line
		@@ -44,17 +44,19 @@ kmmio_fault(struct pt_regs *regs, unsigned long addr)

		static nokprobe_inline int kprobes_fault(struct pt_regs *regs)
		{
		int ret = 0;

		/* kprobe_running() needs smp_processor_id() */
		if (kprobes_built_in() && !user_mode(regs)) {
		preempt_disable();
		if (kprobe_running() && kprobe_fault_handler(regs, 14))
		ret = 1;
		preempt_enable();
		}

		return ret;
		if (!kprobes_built_in())
		return 0;
		if (user_mode(regs))
		return 0;
		/*
		* To be potentially processing a kprobe fault and to be allowed to call
		* kprobe_running(), we have to be non-preemptible.
		*/
		if (preemptible())
		return 0;
		if (!kprobe_running())
		return 0;
		return kprobe_fault_handler(regs, X86_TRAP_PF);
		}

		/*