4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Marcin Nowakowski <marcin.nowakow...@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.nowakow...@imgtec.com>
Cc: linux-m...@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/16296/
Signed-off-by: Ralf Baechle <r...@linux-mips.org>
Signed-off-by: Sasha Levin <alexander.le...@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>
---
 arch/mips/include/asm/kprobes.h |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/arch/mips/include/asm/kprobes.h
+++ b/arch/mips/include/asm/kprobes.h
@@ -40,7 +40,8 @@ typedef union mips_instruction kprobe_op
 
 #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)


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