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From:   Sasha Levin <Alexander.Levin@microsoft.com>
To:     "stable@vger.kernel.org" <stable@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
CC:     Marcin Nowakowski <marcin.nowakowski@imgtec.com>,
        "linux-mips@linux-mips.org" <linux-mips@linux-mips.org>,
        Ralf Baechle <ralf@linux-mips.org>,
        Sasha Levin <Alexander.Levin@microsoft.com>
Subject: [PATCH AUTOSEL for 4.9 009/293] MIPS: kprobes: flush_insn_slot should
 flush only if probe initialised
Thread-Topic: [PATCH AUTOSEL for 4.9 009/293] MIPS: kprobes: flush_insn_slot
 should flush only if probe initialised
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Date:   Mon, 9 Apr 2018 00:22:54 +0000
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From: Marcin Nowakowski <marcin.nowakowski@imgtec.com>

[ Upstream commit 698b851073ddf5a894910d63ca04605e0473414e ]

When ftrace is used with kprobes, it is possible for a kprobe to contain
an invalid location (ie. only initialised to 0 and not to a specific
location in the code). Trying to perform a cache flush on such location
leads to a crash r4k_flush_icache_range().

Fixes: c1bf207d6ee1 ("MIPS: kprobe: Add support.")
Signed-off-by: Marcin Nowakowski <marcin.nowakowski@imgtec.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/16296/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
---
 arch/mips/include/asm/kprobes.h | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/mips/include/asm/kprobes.h b/arch/mips/include/asm/kprobe=
s.h
index daba1f9a4f79..174aedce3167 100644
--- a/arch/mips/include/asm/kprobes.h
+++ b/arch/mips/include/asm/kprobes.h
@@ -40,7 +40,8 @@ typedef union mips_instruction kprobe_opcode_t;
=20
 #define flush_insn_slot(p)						\
 do {									\
-	flush_icache_range((unsigned long)p->addr,			\
+	if (p->addr)							\
+		flush_icache_range((unsigned long)p->addr,		\
 			   (unsigned long)p->addr +			\
 			   (MAX_INSN_SIZE * sizeof(kprobe_opcode_t)));	\
 } while (0)
--=20
2.15.1