On Thu, 20 Jun 2024, Javier Carrasco wrote:
> Use the struct_size macro to calculate the size of the tll, which
> includes a trailing flexible array.
>
> Signed-off-by: Javier Carrasco <javier.carrasco.cruz@xxxxxxxxx>
>
> ---
> The memory allocation used to be carried out in two steps:
>
> tll = devm_kzalloc(dev, sizeof(struct usbtll_omap), GFP_KERNEL);
> tll->ch_clk = devm_kzalloc(dev, sizeof(struct clk *) * tll->nch,
> GFP_KERNEL);
>
> Until commit 16c2004d9e4d ("mfd: omap-usb-tll: Allocate driver data at once")
> turned that into the current allocation:
>
> tll = devm_kzalloc(dev, sizeof(*tll) + sizeof(tll->ch_clk[nch]),
> GFP_KERNEL);
>
> That has surprised me at first glance because I would have expected
> sizeof(tll->ch_clk[nch]) to return the size of a single pointer, not
> being equivalent to 'sizeof(struct clk *) * nch'.
>
> I might be missing/misunderstanding something here because the commit
> is not new, and the error should be noticeable. Moreover, I don't have
> real hardware to test it. Hence why I didn't mark this patch as a fix.
>
> I would be pleased to get feedback about this (why it is right as it is,
> or if that is actually a bug).
You don't need this H/W to test this our for yourself.
Mock-up the structs in a user-space C-program and print out the sizes.
Please report them all to justify the patch.
> ---
> drivers/mfd/omap-usb-tll.c | 3 +--
> 1 file changed, 1 insertion(+), 2 deletions(-)
>
> diff --git a/drivers/mfd/omap-usb-tll.c b/drivers/mfd/omap-usb-tll.c
> index a091e5b0f21d..5f25ac514ff2 100644
> --- a/drivers/mfd/omap-usb-tll.c
> +++ b/drivers/mfd/omap-usb-tll.c
> @@ -230,8 +230,7 @@ static int usbtll_omap_probe(struct platform_device *pdev)
> break;
> }
>
> - tll = devm_kzalloc(dev, sizeof(*tll) + sizeof(tll->ch_clk[nch]),
> - GFP_KERNEL);
> + tll = devm_kzalloc(dev, struct_size(tll, ch_clk, nch), GFP_KERNEL);
> if (!tll) {
> pm_runtime_put_sync(dev);
> pm_runtime_disable(dev);
>
> --
> 2.40.1
>
--
Lee Jones [李琼斯]
