MIPS: kprobes: flush_insn_slot should flush only if probe initialised

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>

diff --git a/arch/mips/include/asm/kprobes.h b/arch/mips/include/asm/kprobes.h
index e6ea4d4..c271e27 100644 (file)
--- 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;
 
 #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)