Re: [PATCH v2] net: rds: Replace strncpy with strscpy in connection setup

[Simon Horman <horms@kernel.org>]

On Sun, Apr 27, 2025 at 12:56:14AM +0530, Shankari wrote:
> Hi Jacub,
> 
> I have implemented the changes in the v2 patch. Thanks for your review.
> 
> On Sun, Apr 27, 2025 at 12:51 AM Shankari Anand
> <shankari.ak0208@gmail.com> wrote:
> >
> > From: Shankari02 <shankari.ak0208@gmail.com>
> >
> > This patch replaces strncpy() with strscpy(), which is the preferred, safer
> > alternative for bounded string copying in the Linux kernel. strscpy() guarantees
> > null-termination as long as the destination buffer is non-zero in size and provides
> > a return value to detect truncation.
> >
> > Padding of the 'transport' field is not necessary because it is treated purely
> > as a null-terminated string and is not used for binary comparisons or direct
> > memory operations that would rely on padding. Therefore, switching to strscpy()
> > is safe and appropriate here.
> >
> > This change is made in accordance with the Linux kernel documentation, which
> > marks strncpy() as deprecated for bounded string operations:
> > https://www.kernel.org/doc/html/latest/process/deprecated.html#strcpy
> >
> > Signed-off-by: Shankari Anand <shankari.ak0208@gmail.com>
> > ---
> >  net/rds/connection.c | 4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/net/rds/connection.c b/net/rds/connection.c
> > index c749c5525b40..fb2f14a1279a 100644
> > --- a/net/rds/connection.c
> > +++ b/net/rds/connection.c
> > @@ -749,7 +749,7 @@ static int rds_conn_info_visitor(struct rds_conn_path *cp, void *buffer)
> >         cinfo->laddr = conn->c_laddr.s6_addr32[3];
> >         cinfo->faddr = conn->c_faddr.s6_addr32[3];
> >         cinfo->tos = conn->c_tos;
> > -       strncpy(cinfo->transport, conn->c_trans->t_name,
> > +       strscpy(cinfo->transport, conn->c_trans->t_name,
> >                 sizeof(cinfo->transport));

Because cinfo->transport is an array it's length is sizeof(cinfo->transport),
as used above. But for the same reason the two-argument version of
strscpy() can be used here.

	strscpy(cinfo->transport, conn->c_trans->t_name);

Similarly if, based on my understanding of Jakub's feedback,
strscpy_pad() should be used.

> >         cinfo->flags = 0;
> >
> > @@ -775,7 +775,7 @@ static int rds6_conn_info_visitor(struct rds_conn_path *cp, void *buffer)
> >         cinfo6->next_rx_seq = cp->cp_next_rx_seq;
> >         cinfo6->laddr = conn->c_laddr;
> >         cinfo6->faddr = conn->c_faddr;
> > -       strncpy(cinfo6->transport, conn->c_trans->t_name,
> > +       strscpy(cinfo6->transport, conn->c_trans->t_name,
> >                 sizeof(cinfo6->transport));

Ditto.

> >         cinfo6->flags = 0;
> >
> > --
> > 2.34.1
> >
>