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    Subject[PATCH AUTOSEL 5.4 039/330] mfd: mfd-core: Protect against NULL call-back function pointer
    Date
    From: Lee Jones <lee.jones@linaro.org>

    [ Upstream commit b195e101580db390f50b0d587b7f66f241d2bc88 ]

    If a child device calls mfd_cell_{en,dis}able() without an appropriate
    call-back being set, we are likely to encounter a panic. Avoid this
    by adding suitable checking.

    Signed-off-by: Lee Jones <lee.jones@linaro.org>
    Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>
    Reviewed-by: Mark Brown <broonie@kernel.org>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    drivers/mfd/mfd-core.c | 10 ++++++++++
    1 file changed, 10 insertions(+)

    diff --git a/drivers/mfd/mfd-core.c b/drivers/mfd/mfd-core.c
    index 23276a80e3b48..96d02b6f06fd8 100644
    --- a/drivers/mfd/mfd-core.c
    +++ b/drivers/mfd/mfd-core.c
    @@ -28,6 +28,11 @@ int mfd_cell_enable(struct platform_device *pdev)
    const struct mfd_cell *cell = mfd_get_cell(pdev);
    int err = 0;

    + if (!cell->enable) {
    + dev_dbg(&pdev->dev, "No .enable() call-back registered\n");
    + return 0;
    + }
    +
    /* only call enable hook if the cell wasn't previously enabled */
    if (atomic_inc_return(cell->usage_count) == 1)
    err = cell->enable(pdev);
    @@ -45,6 +50,11 @@ int mfd_cell_disable(struct platform_device *pdev)
    const struct mfd_cell *cell = mfd_get_cell(pdev);
    int err = 0;

    + if (!cell->disable) {
    + dev_dbg(&pdev->dev, "No .disable() call-back registered\n");
    + return 0;
    + }
    +
    /* only disable if no other clients are using it */
    if (atomic_dec_return(cell->usage_count) == 0)
    err = cell->disable(pdev);
    --
    2.25.1
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