linux-kernel - Re: [PATCH] fs/xfs: replace strncpy with strscpy

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Message-ID: <CAH4c4jJcyA+=x5y3BrW7dQkWOM3bVTepH0W16cm+_CLqHr4hfw@mail.gmail.com>
Date: Tue, 1 Jul 2025 14:18:12 +0530
From: Pranav Tyagi <pranav.tyagi03@...il.com>
To: Brahmajit Das <listout@...tout.xyz>
Cc: Carlos Maiolino <cem@...nel.org>, skhan@...uxfoundation.org, 
	linux-kernel-mentees@...ts.linux.dev, linux-xfs@...r.kernel.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] fs/xfs: replace strncpy with strscpy

On Mon, Jun 30, 2025 at 7:48 PM Brahmajit Das <listout@...tout.xyz> wrote:
>
> On 30.06.2025 14:36, Pranav Tyagi wrote:
> ... snip ...
> > > >       spin_unlock(&mp->m_sb_lock);
> > > >
> > > >       if (copy_to_user(user_label, label, sizeof(label)))
> > > > --
> > > > 2.49.0
> > > >
> >
> > Hi,
> >
> > Thank you for the feedback. I understand that my patch is incorrect and
> > it causes a buffer overrun. The destination buffer is indeed, already, null
> > terminated. Would you like me to send a corrected patch which uses
> > strscpy() (as strncpy() is deprecated)?
> >
> If the destination buffer is already NUL terminated, you can use either
> strtomem or strtomem_pad [0].
>
> [0]: https://docs.kernel.org/core-api/kernel-api.html#c.strncpy
> (Description)

Thank you for the suggestion. On going through [0], I see that,
both, strtomem and strscpy require the src to be null
terminated. As far as I know, sb_fname buffer has a size of
XFSLABEL_MAX (12 bytes). This means no terminating NULL
for the src. So shouldn't memcpy() be the right function to use here?

> > Regret the inconvenience.
> >
> > Regards
> > Pranav Tyagi
> >
>
> --
> Regards,
> listout