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Subject[PATCH 3.16 171/233] MIPS: kprobes: flush_insn_slot should flush only if probe initialised
3.16.48-rc1 review patch.  If anyone has any objections, please let me know.

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

From: Marcin Nowakowski <marcin.nowakowski@imgtec.com>

commit 698b851073ddf5a894910d63ca04605e0473414e upstream.

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: Ben Hutchings <ben@decadent.org.uk>
---
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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