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    Subject[PATCH 4.9 64/66] bpf: fix divides by zero
    Date
    4.9-stable review patch.  If anyone has any objections, please let me know.

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

    From: Eric Dumazet <edumazet@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 <edumazet@google.com>
    Reported-by: syzbot <syzkaller@googlegroups.com>
    Signed-off-by: Alexei Starovoitov <ast@kernel.org>
    Signed-off-by: Greg Kroah-Hartman <gregkh@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);

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