Re: [PATCH v1 1/1] SUNRPC: Make enough room in servername[] for AF_UNIX addresses

[NeilBrown]

On Tue, 24 Sep 2024, Mirsad Todorovac wrote:
> GCC 13.2.0 reported with W=1 build option the following warning:

See
  https://lore.kernel.org/all/20240814093853.48657-1-kunwu.chan@xxxxxxxxx/

I don't think anyone really cares about this one.

NeilBrown


> 
> net/sunrpc/clnt.c: In function ‘rpc_create’:
> net/sunrpc/clnt.c:582:75: warning: ‘%s’ directive output may be truncated writing up to 107 bytes into \
> 					a region of size 48 [-Wformat-truncation=]
>   582 |                                 snprintf(servername, sizeof(servername), "%s",
>       |                                                                           ^~
> net/sunrpc/clnt.c:582:33: note: ‘snprintf’ output between 1 and 108 bytes into a destination of size 48
>   582 |                                 snprintf(servername, sizeof(servername), "%s",
>       |                                 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>   583 |                                          sun->sun_path);
>       |                                          ~~~~~~~~~~~~~~
> 
>    548         };
>  → 549         char servername[48];
>    550         struct rpc_clnt *clnt;
>    551         int i;
>    552
>    553         if (args->bc_xprt) {
>    554                 WARN_ON_ONCE(!(args->protocol & XPRT_TRANSPORT_BC));
>    555                 xprt = args->bc_xprt->xpt_bc_xprt;
>    556                 if (xprt) {
>    557                         xprt_get(xprt);
>    558                         return rpc_create_xprt(args, xprt);
>    559                 }
>    560         }
>    561
>    562         if (args->flags & RPC_CLNT_CREATE_INFINITE_SLOTS)
>    563                 xprtargs.flags |= XPRT_CREATE_INFINITE_SLOTS;
>    564         if (args->flags & RPC_CLNT_CREATE_NO_IDLE_TIMEOUT)
>    565                 xprtargs.flags |= XPRT_CREATE_NO_IDLE_TIMEOUT;
>    566         /*
>    567          * If the caller chooses not to specify a hostname, whip
>    568          * up a string representation of the passed-in address.
>    569          */
>    570         if (xprtargs.servername == NULL) {
>    571                 struct sockaddr_un *sun =
>    572                                 (struct sockaddr_un *)args->address;
>    573                 struct sockaddr_in *sin =
>    574                                 (struct sockaddr_in *)args->address;
>    575                 struct sockaddr_in6 *sin6 =
>    576                                 (struct sockaddr_in6 *)args->address;
>    577
>    578                 servername[0] = '\0';
>    579                 switch (args->address->sa_family) {
>  → 580                 case AF_LOCAL:
>  → 581                         if (sun->sun_path[0])
>  → 582                                 snprintf(servername, sizeof(servername), "%s",
>  → 583                                          sun->sun_path);
>  → 584                         else
>  → 585                                 snprintf(servername, sizeof(servername), "@%s",
>  → 586                                          sun->sun_path+1);
>  → 587                         break;
>    588                 case AF_INET:
>    589                         snprintf(servername, sizeof(servername), "%pI4",
>    590                                  &sin->sin_addr.s_addr);
>    591                         break;
>    592                 case AF_INET6:
>    593                         snprintf(servername, sizeof(servername), "%pI6",
>    594                                  &sin6->sin6_addr);
>    595                         break;
>    596                 default:
>    597                         /* caller wants default server name, but
>    598                          * address family isn't recognized. */
>    599                         return ERR_PTR(-EINVAL);
>    600                 }
>    601                 xprtargs.servername = servername;
>    602         }
>    603
>    604         xprt = xprt_create_transport(&xprtargs);
>    605         if (IS_ERR(xprt))
>    606                 return (struct rpc_clnt *)xprt;
> 
> After the address family AF_LOCAL was added in the commit 176e21ee2ec89, the old hard-coded
> size for servername of char servername[48] no longer fits. The maximum AF_UNIX address size
> has now grown to UNIX_PATH_MAX defined as 108 in "include/uapi/linux/un.h" .
> 
> The lines 580-587 were added later, addressing the leading zero byte '\0', but did not fix
> the hard-coded servername limit.
> 
> The AF_UNIX address was truncated to 47 bytes + terminating null byte. This patch will fix the
> servername in AF_UNIX family to the maximum permitted by the system:
> 
>    548         };
>  → 549         char servername[UNIX_PATH_MAX];
>    550         struct rpc_clnt *clnt;
> 
> Fixes: 4388ce05fa38b ("SUNRPC: support abstract unix socket addresses")
> Fixes: 510deb0d7035d ("SUNRPC: rpc_create() default hostname should support AF_INET6 addresses")
> Fixes: 176e21ee2ec89 ("SUNRPC: Support for RPC over AF_LOCAL transports")
> Cc: Neil Brown <neilb@xxxxxxx>
> Cc: Chuck Lever <chuck.lever@xxxxxxxxxx>
> Cc: Trond Myklebust <trondmy@xxxxxxxxxx>
> Cc: Anna Schumaker <anna@xxxxxxxxxx>
> Cc: Jeff Layton <jlayton@xxxxxxxxxx>
> Cc: Olga Kornievskaia <okorniev@xxxxxxxxxx>
> Cc: Dai Ngo <Dai.Ngo@xxxxxxxxxx>
> Cc: Tom Talpey <tom@xxxxxxxxxx>
> Cc: "David S. Miller" <davem@xxxxxxxxxxxxx>
> Cc: Eric Dumazet <edumazet@xxxxxxxxxx>
> Cc: Jakub Kicinski <kuba@xxxxxxxxxx>
> Cc: Paolo Abeni <pabeni@xxxxxxxxxx>
> Cc: linux-nfs@xxxxxxxxxxxxxxx
> Cc: netdev@xxxxxxxxxxxxxxx
> Cc: linux-kernel@xxxxxxxxxxxxxxx
> Signed-off-by: Mirsad Todorovac <mtodorovac69@xxxxxxxxx>
> ---
>  v1:
> 	initial version.
> 
>  net/sunrpc/clnt.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/net/sunrpc/clnt.c b/net/sunrpc/clnt.c
> index 09f29a95f2bc..67099719893e 100644
> --- a/net/sunrpc/clnt.c
> +++ b/net/sunrpc/clnt.c
> @@ -546,7 +546,7 @@ struct rpc_clnt *rpc_create(struct rpc_create_args *args)
>  		.connect_timeout = args->connect_timeout,
>  		.reconnect_timeout = args->reconnect_timeout,
>  	};
> -	char servername[48];
> +	char servername[UNIX_PATH_MAX];
>  	struct rpc_clnt *clnt;
>  	int i;
>  
> -- 
> 2.43.0
> 
>