Re: [PATCH] firewire: core: clean up modalias buffer handling

[Takashi Sakamoto]

Hi,

Thanks for sending your patch.

On Sun, Mar 29, 2026 at 11:19:40PM +0200, Thorsten Blum wrote:
> Use scnprintf() in get_modalias() to return the number of characters
> actually written to the destination buffer.
> 
> Also reserve space for the trailing newline in modalias_show() and
> append it explicitly, instead of using strcpy() and relying on the
> formatted modalias to fit within PAGE_SIZE.
> 
> While the current code is safe, this makes the sysfs buffer handling
> more explicit and consistent.
> 
> Signed-off-by: Thorsten Blum <thorsten.blum@xxxxxxxxx>
> ---
>  drivers/firewire/core-device.c | 11 ++++++-----
>  1 file changed, 6 insertions(+), 5 deletions(-)

I previously considered using sysfs_emit(_at)() in the code, but decided
against it because the code is called in both sysfs and the workqueue
context of firewire devices. The buffer size differs between these cases
(either PAGE_SIZE or 64).

In any case, as you already noted, the current code is enough safe. The
total length of formatted string is fixed (= 41 + 1) by the format
template, so it is unlikely to cause issues. I have little motivation to
change it.


Thanks

Takashi Sakamoto