Re: [PATCH] drivers: pnp: proc.c: Handle errors while attaching devices

Barnabás Pőcze
2021-04-25T01:06:31Z

Hi

2021. április 24., szombat 21:43 keltezéssel, Anupama K Patil írta:

> isapnp_proc_init() does not look at the return value from
> isapnp_proc_attach_device(). Check for this return value in
> isapnp_proc_detach_device().
>
> Cleanup in isapnp_proc_detach_device and
> isapnp_proc_detach_bus() for cleanup.
>
> Changed sprintf() to the kernel-space function scnprintf() as it returns
> the actual number of bytes written.
>
> Removed unnecessary variables de, e of type 'struct proc_dir_entry' to
> save memory.
>
> Suggested-by: Shuah Khan <skhan@linuxfoundation.org>
> Co-developed-by: B K Karthik <bkkarthik@pesu.pes.edu>
> Signed-off-by: B K Karthik <bkkarthik@pesu.pes.edu>
> Signed-off-by: Anupama K Patil <anupamakpatil123@gmail.com>
> ---
> drivers/pnp/isapnp/proc.c | 40 +++++++++++++++++++++++++++++----------
> 1 file changed, 30 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/pnp/isapnp/proc.c b/drivers/pnp/isapnp/proc.c
> index 785a796430fa..46ebc24175b7 100644
> --- a/drivers/pnp/isapnp/proc.c
> +++ b/drivers/pnp/isapnp/proc.c
> @@ -54,34 +54,54 @@ static const struct proc_ops isapnp_proc_bus_proc_ops = {
> .proc_read = isapnp_proc_bus_read,
> };
>
> +static int isapnp_proc_detach_device(struct pnp_dev *dev)
> +{
> + proc_remove(dev->procent);
> + dev->procent = NULL;
> + return 0;
> +}
> +
> +static int isapnp_proc_detach_bus(struct pnp_card *bus)
> +{
> + proc_remove(bus->procdir);

Is there any reason for not setting `bus->procdir` to `NULL`
similarly to the previous function?

> + return 0;
> +}
> +

Is there any reason why the previous two functions return something? It doesn't
seem to be necessary.

> static int isapnp_proc_attach_device(struct pnp_dev *dev)
> {
> struct pnp_card *bus = dev->card;
> - struct proc_dir_entry *de, *e;
> char name[16];
>
> - if (!(de = bus->procdir)) {
> - sprintf(name, "%02x", bus->number);
> - de = bus->procdir = proc_mkdir(name, isapnp_proc_bus_dir);
> - if (!de)
> + if (!bus->procdir) {
> + scnprintf(name, 16, "%02x", bus->number);

I think `sizeof(name)` would be preferable to hard-coding 16.

> + bus->procdir = proc_mkdir(name, isapnp_proc_bus_dir);
> + if (!bus->procdir)
> return -ENOMEM;
> }
> - sprintf(name, "%02x", dev->number);
> - e = dev->procent = proc_create_data(name, S_IFREG | S_IRUGO, de,
> + scnprintf(name, 16, "%02x", dev->number);

Here as well.

> + dev->procent = proc_create_data(name, S_IFREG | S_IRUGO, bus->procdir,
> &isapnp_proc_bus_proc_ops, dev);

Please align the continuation properly.

> - if (!e)
> + if (!dev->procent) {
> + isapnp_proc_detach_bus(bus);

I'm not sure if this should be here. If I'm not mistaken, the code
creates a procfs directory for a bus when it first sees a `pnp_dev` from that bus.
This call removes the whole directory for the bus, and with that, the files of
those `pnp_dev`s which were successfully created earlier.

> return -ENOMEM;
> - proc_set_size(e, 256);
> + }
> + proc_set_size(dev->procent, 256);
> return 0;
> }
>
> int __init isapnp_proc_init(void)
> {
> struct pnp_dev *dev;
> + int dev_attach;
>
> isapnp_proc_bus_dir = proc_mkdir("bus/isapnp", NULL);

You could add a check to see if this `proc_mkdir()` call succeeds, and
possibly return early if it does not.

> protocol_for_each_dev(&isapnp_protocol, dev) {
> - isapnp_proc_attach_device(dev);
> + dev_attach = isapnp_proc_attach_device(dev);
> + if (!dev_attach) {

`isapnp_proc_attach_device()` returns 0 on success, so the condition should be inverted.
And maybe `err` or something like that would be a better name than `dev_attach`.

> + pr_info("procfs: pnp: Unable to attach the device, not enough memory");

If I'm not mistaken, allocation failures are logged, so this is probably not needed.

> + isapnp_proc_detach_device(dev);

I'm also not sure if this is needed here. If `isapnp_proc_attach_device()` returns
an error, then `dev->procdir` could not have been "created". In other words,
if the execution reaches this point, `proc_create_data()` could not have succeeded
because either it had not yet been called or it had failed.

> + return -ENOMEM;

It is usually preferable to return the error code you receive. E.g.:

err = isapnp_proc_attach_device(...);
if (err) {
...
return err;
}

> + }
> }
> return 0;
> }
> --
> 2.25.1
>

Regards,
Barnabás Pőcze