This is a note to let you know that I've just added the patch titled mfd: mfd-core: Protect against NULL call-back function pointer to the 4.9-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: mfd-mfd-core-protect-against-null-call-back-function.patch and it can be found in the queue-4.9 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. commit a1924f241d66df0f3db694ba79de26fd23a6c518 Author: Lee Jones <lee.jones@xxxxxxxxxx> Date: Mon Oct 21 10:16:34 2019 +0100 mfd: mfd-core: Protect against NULL call-back function pointer [ 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@xxxxxxxxxx> Reviewed-by: Daniel Thompson <daniel.thompson@xxxxxxxxxx> Reviewed-by: Mark Brown <broonie@xxxxxxxxxx> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> diff --git a/drivers/mfd/mfd-core.c b/drivers/mfd/mfd-core.c index 5c8ed2150c8bf..fb687368ac98c 100644 --- a/drivers/mfd/mfd-core.c +++ b/drivers/mfd/mfd-core.c @@ -32,6 +32,11 @@ 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); @@ -49,6 +54,11 @@ 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);