linux-kernel - [PATCH 2/2] x86,kprobes: WARN if kprobes tries to handle a fault

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Date:   Tue, 25 May 2021 09:25:20 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     mhiramat@...nel.org
Cc:     linux-kernel@...r.kernel.org, peterz@...radead.org,
        mingo@...nel.org, rostedt@...dmis.org,
        naveen.n.rao@...ux.vnet.ibm.com, ananth@...ux.ibm.com,
        x86@...nel.org
Subject: [PATCH 2/2] x86,kprobes: WARN if kprobes tries to handle a fault

With the removal of kprobe::handle_fault there is no reason left that
kprobe_page_fault() would ever return true on x86, make sure it
doesn't happen by accident.

Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
---
 arch/x86/mm/fault.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -1186,7 +1186,7 @@ do_kern_addr_fault(struct pt_regs *regs,
 		return;
 
 	/* kprobes don't want to hook the spurious faults: */
-	if (kprobe_page_fault(regs, X86_TRAP_PF))
+	if (WARN_ON_ONCE(kprobe_page_fault(regs, X86_TRAP_PF)))
 		return;
 
 	/*
@@ -1239,7 +1239,7 @@ void do_user_addr_fault(struct pt_regs *
 	}
 
 	/* kprobes don't want to hook the spurious faults: */
-	if (unlikely(kprobe_page_fault(regs, X86_TRAP_PF)))
+	if (WARN_ON_ONCE(kprobe_page_fault(regs, X86_TRAP_PF)))
 		return;
 
 	/*