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

[Mirsad Todorovac <mtodorovac69@xxxxxxxxx>]

GCC 13.2.0 reported with W=1 build option the following warning:

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