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SubjectRE: [PATCH v3 3/3] PCI: endpoint: Fix find_first_zero_bit() usage
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From: Niklas Cassel
> Sent: 27 November 2017 15:50
> find_first_zero_bit()'s parameter 'size' is defined in bits,
> not in bytes.
>
> Calling find_first_zero_bit() with the wrong size unit
> will lead to insidious bugs.
>
> Fix this by calling find_first_zero_bit() with size
> BITS_PER_LONG, rather than sizeof().
>
> Also add proper error handling for find_first_zero_bit(),
> since this was missing.
>
> Fixes: d74679911610 ("PCI: endpoint: Introduce configfs entry for configuring EP functions")
> Signed-off-by: Niklas Cassel <niklas.cassel@axis.com>
> ---
> drivers/pci/endpoint/pci-ep-cfs.c | 8 +++++++-
> 1 file changed, 7 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/pci/endpoint/pci-ep-cfs.c b/drivers/pci/endpoint/pci-ep-cfs.c
> index e1f5adc9e113..0a22a7976580 100644
> --- a/drivers/pci/endpoint/pci-ep-cfs.c
> +++ b/drivers/pci/endpoint/pci-ep-cfs.c
> @@ -109,7 +109,12 @@ static int pci_epc_epf_link(struct config_item *epc_item,
> return ret;
>
> func_no = find_first_zero_bit(&epc_group->function_num_map,
> - sizeof(epc_group->function_num_map));
> + BITS_PER_LONG);

Surely this should be either 8 * sizeof() or you should use ffz()
that takes a numeric argument rather than the function designed
for arbitrary size bitmaps.

David

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