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    Subject[PATCH AUTOSEL 4.19 053/252] clk: qcom: rcg2: Don't crash if our parent can't be found; return an error
    Date
    From: Douglas Anderson <dianders@chromium.org>

    [ Upstream commit 908b050114d8fefdddc57ec9fbc213c3690e7f5f ]

    When I got my clock parenting slightly wrong I ended up with a crash
    that looked like this:

    Unable to handle kernel NULL pointer dereference at virtual
    address 0000000000000000
    ...
    pc : clk_hw_get_rate+0x14/0x44
    ...
    Call trace:
    clk_hw_get_rate+0x14/0x44
    _freq_tbl_determine_rate+0x94/0xfc
    clk_rcg2_determine_rate+0x2c/0x38
    clk_core_determine_round_nolock+0x4c/0x88
    clk_core_round_rate_nolock+0x6c/0xa8
    clk_core_round_rate_nolock+0x9c/0xa8
    clk_core_set_rate_nolock+0x70/0x180
    clk_set_rate+0x3c/0x6c
    of_clk_set_defaults+0x254/0x360
    platform_drv_probe+0x28/0xb0
    really_probe+0x120/0x2dc
    driver_probe_device+0x64/0xfc
    device_driver_attach+0x4c/0x6c
    __driver_attach+0xac/0xc0
    bus_for_each_dev+0x84/0xcc
    driver_attach+0x2c/0x38
    bus_add_driver+0xfc/0x1d0
    driver_register+0x64/0xf8
    __platform_driver_register+0x4c/0x58
    msm_drm_register+0x5c/0x60
    ...

    It turned out that clk_hw_get_parent_by_index() was returning NULL and
    we weren't checking. Let's check it so that we don't crash.

    Fixes: ac269395cdd8 ("clk: qcom: Convert to clk_hw based provider APIs")
    Signed-off-by: Douglas Anderson <dianders@chromium.org>
    Reviewed-by: Matthias Kaehlcke <mka@chromium.org>
    Link: https://lkml.kernel.org/r/20200203103049.v4.1.I7487325fe8e701a68a07d3be8a6a4b571eca9cfa@changeid
    Signed-off-by: Stephen Boyd <sboyd@kernel.org>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    drivers/clk/qcom/clk-rcg2.c | 3 +++
    1 file changed, 3 insertions(+)

    diff --git a/drivers/clk/qcom/clk-rcg2.c b/drivers/clk/qcom/clk-rcg2.c
    index 51b2388d80ac9..ee693e15d9ebc 100644
    --- a/drivers/clk/qcom/clk-rcg2.c
    +++ b/drivers/clk/qcom/clk-rcg2.c
    @@ -203,6 +203,9 @@ static int _freq_tbl_determine_rate(struct clk_hw *hw, const struct freq_tbl *f,

    clk_flags = clk_hw_get_flags(hw);
    p = clk_hw_get_parent_by_index(hw, index);
    + if (!p)
    + return -EINVAL;
    +
    if (clk_flags & CLK_SET_RATE_PARENT) {
    rate = f->freq;
    if (f->pre_div) {
    --
    2.20.1
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