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    Subject[PATCH 4.19 100/114] bpf: Fix preempt_enable_no_resched() abuse
    Date
    [ Upstream commit 0edd6b64d1939e9e9168ff27947995bb7751db5d ]

    Unless the very next line is schedule(), or implies it, one must not use
    preempt_enable_no_resched(). It can cause a preemption to go missing and
    thereby cause arbitrary delays, breaking the PREEMPT=y invariant.

    Cc: Roman Gushchin <guro@fb.com>
    Cc: Alexei Starovoitov <ast@kernel.org>
    Cc: Daniel Borkmann <daniel@iogearbox.net>
    Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
    Signed-off-by: Alexei Starovoitov <ast@kernel.org>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    include/linux/bpf.h | 2 +-
    1 file changed, 1 insertion(+), 1 deletion(-)

    diff --git a/include/linux/bpf.h b/include/linux/bpf.h
    index 523481a3471b5..fd95f2efe5f32 100644
    --- a/include/linux/bpf.h
    +++ b/include/linux/bpf.h
    @@ -400,7 +400,7 @@ int bpf_prog_array_copy(struct bpf_prog_array __rcu *old_array,
    } \
    _out: \
    rcu_read_unlock(); \
    - preempt_enable_no_resched(); \
    + preempt_enable(); \
    _ret; \
    })

    --
    2.20.1


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