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    Subject[PATCH 5.16 0961/1039] clk: Emit a stern warning with writable debugfs enabled
    Date
    From: Stephen Boyd <sboyd@kernel.org>

    commit 489a71964f9d74e697a12cd0ace20ed829eb1f93 upstream.

    We don't want vendors to be enabling this part of the clk code and
    shipping it to customers. Exposing the ability to change clk frequencies
    and parents via debugfs is potentially damaging to the system if folks
    don't know what they're doing. Emit a strong warning so that the message
    is clear: don't enable this outside of development systems.

    Fixes: 37215da5553e ("clk: Add support for setting clk_rate via debugfs")
    Cc: Geert Uytterhoeven <geert+renesas@glider.be>
    Link: https://lore.kernel.org/r/20211210014237.2130300-1-sboyd@kernel.org
    Signed-off-by: Stephen Boyd <sboyd@kernel.org>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    drivers/clk/clk.c | 18 ++++++++++++++++++
    1 file changed, 18 insertions(+)

    --- a/drivers/clk/clk.c
    +++ b/drivers/clk/clk.c
    @@ -3343,6 +3343,24 @@ static int __init clk_debug_init(void)
    {
    struct clk_core *core;

    +#ifdef CLOCK_ALLOW_WRITE_DEBUGFS
    + pr_warn("\n");
    + pr_warn("********************************************************************\n");
    + pr_warn("** NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE **\n");
    + pr_warn("** **\n");
    + pr_warn("** WRITEABLE clk DebugFS SUPPORT HAS BEEN ENABLED IN THIS KERNEL **\n");
    + pr_warn("** **\n");
    + pr_warn("** This means that this kernel is built to expose clk operations **\n");
    + pr_warn("** such as parent or rate setting, enabling, disabling, etc. **\n");
    + pr_warn("** to userspace, which may compromise security on your system. **\n");
    + pr_warn("** **\n");
    + pr_warn("** If you see this message and you are not debugging the **\n");
    + pr_warn("** kernel, report this immediately to your vendor! **\n");
    + pr_warn("** **\n");
    + pr_warn("** NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE **\n");
    + pr_warn("********************************************************************\n");
    +#endif
    +
    rootdir = debugfs_create_dir("clk", NULL);

    debugfs_create_file("clk_summary", 0444, rootdir, &all_lists,

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