4.17-stable review patch. If anyone has any objections, please let me know.
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From: Douglas Anderson dianders@chromium.org
[ Upstream commit 87ed1405ef09d29a14df43295f7b6a93b63bfe6e ]
In commit ca04d9d3e1b1 ("phy: qcom-qusb2: New driver for QUSB2 PHY on Qcom chips") you can see a call like:
devm_nvmem_cell_get(dev, NULL);
Note that the cell ID passed to the function is NULL. This is because the qcom-qusb2 driver is expected to work only on systems where the PHY node is hooked up via device-tree and is nameless.
This works OK for the most part. The first thing nvmem_cell_get() does is to call of_nvmem_cell_get() and there it's documented that a NULL name is fine. The problem happens when the call to of_nvmem_cell_get() returns -EINVAL. In such a case we'll fall back to nvmem_cell_get_from_list() and eventually might (if nvmem_cells isn't an empty list) crash with something that looks like:
strcmp nvmem_find_cell __nvmem_device_get nvmem_cell_get_from_list nvmem_cell_get devm_nvmem_cell_get qusb2_phy_probe
There are several different ways we could fix this problem:
One could argue that perhaps the qcom-qusb2 driver should be changed to use of_nvmem_cell_get() which is allowed to have a NULL name. In that case, we'd need to add a patche to introduce devm_of_nvmem_cell_get() since the qcom-qusb2 driver is using devm managed resources.
One could also argue that perhaps we could just add a name to qcom-qusb2. That would be OK but I believe it effectively changes the device tree bindings, so maybe it's a no-go.
In this patch I have chosen to fix the problem by simply not crashing when a NULL cell_id is passed to nvmem_cell_get().
NOTE: that for the qcom-qusb2 driver the "nvmem-cells" property is defined to be optional and thus it's expected to be a common case that we would hit this crash and this is more than just a theoretical fix.
Fixes: ca04d9d3e1b1 ("phy: qcom-qusb2: New driver for QUSB2 PHY on Qcom chips") Signed-off-by: Douglas Anderson dianders@chromium.org Signed-off-by: Srinivas Kandagatla srinivas.kandagatla@linaro.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org Signed-off-by: Sasha Levin alexander.levin@microsoft.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/nvmem/core.c | 4 ++++ 1 file changed, 4 insertions(+)
--- a/drivers/nvmem/core.c +++ b/drivers/nvmem/core.c @@ -924,6 +924,10 @@ struct nvmem_cell *nvmem_cell_get(struct return cell; }
+ /* NULL cell_id only allowed for device tree; invalid otherwise */ + if (!cell_id) + return ERR_PTR(-EINVAL); + return nvmem_cell_get_from_list(cell_id); } EXPORT_SYMBOL_GPL(nvmem_cell_get);