linux-kernel - [PATCH 4.14 172/211] arm64: fix for bad_mode() handler to always result in panic

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Message-Id: <20191127203110.120376346@linuxfoundation.org>
Date:   Wed, 27 Nov 2019 21:31:45 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Hari Vyas <hari.vyas@...adcom.com>,
        Will Deacon <will.deacon@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Lee Jones <lee.jones@...aro.org>
Subject: [PATCH 4.14 172/211] arm64: fix for bad_mode() handler to always result in panic

From: Hari Vyas <hari.vyas@...adcom.com>

commit e4ba15debcfd27f60d43da940a58108783bff2a6 upstream.

The bad_mode() handler is called if we encounter an uunknown exception,
with the expectation that the subsequent call to panic() will halt the
system. Unfortunately, if the exception calling bad_mode() is taken from
EL0, then the call to die() can end up killing the current user task and
calling schedule() instead of falling through to panic().

Remove the die() call altogether, since we really want to bring down the
machine in this "impossible" case.

Signed-off-by: Hari Vyas <hari.vyas@...adcom.com>
Signed-off-by: Will Deacon <will.deacon@....com>
Signed-off-by: Catalin Marinas <catalin.marinas@....com>
Signed-off-by: Lee Jones <lee.jones@...aro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 arch/arm64/kernel/traps.c |    1 -
 1 file changed, 1 deletion(-)

--- a/arch/arm64/kernel/traps.c
+++ b/arch/arm64/kernel/traps.c
@@ -648,7 +648,6 @@ asmlinkage void bad_mode(struct pt_regs
 		handler[reason], smp_processor_id(), esr,
 		esr_get_class_string(esr));
 
-	die("Oops - bad mode", regs, 0);
 	local_irq_disable();
 	panic("bad mode");
 }