[PATCH 4.9 64/66] bpf: fix divides by zero

[Greg Kroah-Hartman]

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

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

From: Eric Dumazet <eduma...@google.com>

[ upstream commit c366287ebd698ef5e3de300d90cd62ee9ee7373e ]

Divides by zero are not nice, lets avoid them if possible.

Also do_div() seems not needed when dealing with 32bit operands,
but this seems a minor detail.

Fixes: bd4cf0ed331a ("net: filter: rework/optimize internal BPF interpreter's 
instruction set")
Signed-off-by: Eric Dumazet <eduma...@google.com>
Reported-by: syzbot <syzkal...@googlegroups.com>
Signed-off-by: Alexei Starovoitov <a...@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>
---
 kernel/bpf/core.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c
@@ -642,7 +642,7 @@ select_insn:
                DST = tmp;
                CONT;
        ALU_MOD_X:
-               if (unlikely(SRC == 0))
+               if (unlikely((u32)SRC == 0))
                        return 0;
                tmp = (u32) DST;
                DST = do_div(tmp, (u32) SRC);
@@ -661,7 +661,7 @@ select_insn:
                DST = div64_u64(DST, SRC);
                CONT;
        ALU_DIV_X:
-               if (unlikely(SRC == 0))
+               if (unlikely((u32)SRC == 0))
                        return 0;
                tmp = (u32) DST;
                do_div(tmp, (u32) SRC);