linux-kernel - Re: [PATCH] net: rds: replace strncpy with memcpy

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Message-ID: <32b8d4635b8f15cce3ae898cc480616428bc93ba.camel@oracle.com>
Date: Tue, 8 Apr 2025 22:45:24 +0000
From: Allison Henderson <allison.henderson@...cle.com>
To: "linux-rdma@...r.kernel.org" <linux-rdma@...r.kernel.org>,
        "shannon.nelson@....com" <shannon.nelson@....com>,
        "davem@...emloft.net"
	<davem@...emloft.net>,
        "dsahern@...nel.org" <dsahern@...nel.org>,
        "linux-kernel-mentees@...ts.linux.dev"
	<linux-kernel-mentees@...ts.linux.dev>,
        "pranav.tyagi03@...il.com"
	<pranav.tyagi03@...il.com>,
        "rds-devel@....oracle.com"
	<rds-devel@....oracle.com>,
        "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>,
        "pabeni@...hat.com" <pabeni@...hat.com>,
        "horms@...nel.org" <horms@...nel.org>,
        "edumazet@...gle.com"
	<edumazet@...gle.com>,
        "kuba@...nel.org" <kuba@...nel.org>,
        "skhan@...uxfoundation.org" <skhan@...uxfoundation.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: [PATCH] net: rds: replace strncpy with memcpy

On Tue, 2025-04-08 at 14:18 -0700, Nelson, Shannon wrote:
> On 4/8/2025 12:41 PM, Pranav Tyagi wrote:
> > 
> > Replace deprecated strncpy() function with memcpy()
> 
> I suspect that strtomem() is a better answer here than a raw memcpy() - 
> it already has all the strnlen() and min() stuff baked into it, along 
> with some other compile-time checking.
> 
> > as the destination buffer is length bounded
> > and not required to be NUL-terminated
> 
> Are you sure that null-termination is not required?  I'm not familiar 
> with this bit of code, but the definitions of both of the .transport[] 
> fields do say /* null term ascii */
> 
> sln
> 

Hi all,

It appears that the transport names are null-terminated. Looking at rds_ib_transport, rds_tcp_transport, and
rds_loop_transport, the t_name member is initialized to "infiniband", "tcp", or "loop", respectively— which include the
null terminator. Given that, I think strscpy seems to be the appropriate function to use here.

However, it looks like Baris has already submitted a similar patch yesterday, and unfortunately, we can't accept both.
That said, thank you very much for your contribution—we really appreciate it! 😊

Allison

> > 
> > Signed-off-by: Pranav Tyagi <pranav.tyagi03@...il.com>
> > ---
> >   net/rds/connection.c | 6 ++----
> >   1 file changed, 2 insertions(+), 4 deletions(-)
> > 
> > diff --git a/net/rds/connection.c b/net/rds/connection.c
> > index c749c5525b40..3718c3edb32e 100644
> > --- a/net/rds/connection.c
> > +++ b/net/rds/connection.c
> > @@ -749,8 +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,
> > -               sizeof(cinfo->transport));
> > +       memcpy(cinfo->transport, conn->c_trans->t_name, min(sizeof(cinfo->transport), strnlen(conn->c_trans->t_name, sizeof(cinfo->transport))));
> >          cinfo->flags = 0;
> > 
> >          rds_conn_info_set(cinfo->flags, test_bit(RDS_IN_XMIT, &cp->cp_flags),
> > @@ -775,8 +774,7 @@ 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,
> > -               sizeof(cinfo6->transport));
> > +       memcpy(cinfo6->transport, conn->c_trans->t_name, min(sizeof(cinfo6->transport), strnlen(conn->c_trans->t_name, sizeof(cinfo6->transport))));
> >          cinfo6->flags = 0;
> > 
> >          rds_conn_info_set(cinfo6->flags, test_bit(RDS_IN_XMIT, &cp->cp_flags),
> > --
> > 2.49.0
> > 
> > 
> 
>