NLM: Shrink the maximum request size of NLM4 requests

NLM version 4 requests estimate the call and reply header sizes rather
conservatively, using the very maximum size allowed in the protocol even
though Linux always uses only a small fraction of the allowable space.

Reduce the size of caller and lock arguments to conserve RPC buffer space
while XDR encoding NLM4 arguments.  Add compile-time checks to ensure the
hostname string won't overflow NLM protocol maximums.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

diff --git a/fs/lockd/xdr.c b/fs/lockd/xdr.c
index 34dae5d70738bff79bc78945fd647dc4f16bdbca..6aac4b2c9ff0a896813bcf76ddf274cefe38de14 100644 (file)
--- a/fs/lockd/xdr.c
+++ b/fs/lockd/xdr.c
@@ -510,17 +510,20 @@ nlmclt_decode_res(struct rpc_rqst *req, __be32 *p, struct nlm_res *resp)
        return 0;
 }
 
+#if (NLMCLNT_OHSIZE > XDR_MAX_NETOBJ)
+#  error "NLM host name cannot be larger than XDR_MAX_NETOBJ!"
+#endif
+
 /*
  * Buffer requirements for NLM
  */
 #define NLM_void_sz            0
 #define NLM_cookie_sz          1+XDR_QUADLEN(NLM_MAXCOOKIELEN)
-#define NLM_caller_sz          1+XDR_QUADLEN(sizeof(utsname()->nodename))
-#define NLM_netobj_sz          1+XDR_QUADLEN(XDR_MAX_NETOBJ)
-/* #define NLM_owner_sz                1+XDR_QUADLEN(NLM_MAXOWNER) */
+#define NLM_caller_sz          1+XDR_QUADLEN(NLMCLNT_OHSIZE)
+#define NLM_owner_sz           1+XDR_QUADLEN(NLMCLNT_OHSIZE)
 #define NLM_fhandle_sz         1+XDR_QUADLEN(NFS2_FHSIZE)
-#define NLM_lock_sz            3+NLM_caller_sz+NLM_netobj_sz+NLM_fhandle_sz
-#define NLM_holder_sz          4+NLM_netobj_sz
+#define NLM_lock_sz            3+NLM_caller_sz+NLM_owner_sz+NLM_fhandle_sz
+#define NLM_holder_sz          4+NLM_owner_sz
 
 #define NLM_testargs_sz                NLM_cookie_sz+1+NLM_lock_sz
 #define NLM_lockargs_sz                NLM_cookie_sz+4+NLM_lock_sz

diff --git a/fs/lockd/xdr4.c b/fs/lockd/xdr4.c
index a78240551219a91ba8d5a34eff83ed8002331bb6..7c8b679c394cc1f42b7c60274868923ad68c6eda 100644 (file)
--- a/fs/lockd/xdr4.c
+++ b/fs/lockd/xdr4.c
@@ -516,17 +516,24 @@ nlm4clt_decode_res(struct rpc_rqst *req, __be32 *p, struct nlm_res *resp)
        return 0;
 }
 
+#if (NLMCLNT_OHSIZE > XDR_MAX_NETOBJ)
+#  error "NLM host name cannot be larger than XDR_MAX_NETOBJ!"
+#endif
+
+#if (NLMCLNT_OHSIZE > NLM_MAXSTRLEN)
+#  error "NLM host name cannot be larger than NLM's maximum string length!"
+#endif
+
 /*
  * Buffer requirements for NLM
  */
 #define NLM4_void_sz           0
 #define NLM4_cookie_sz         1+XDR_QUADLEN(NLM_MAXCOOKIELEN)
-#define NLM4_caller_sz         1+XDR_QUADLEN(NLM_MAXSTRLEN)
-#define NLM4_netobj_sz         1+XDR_QUADLEN(XDR_MAX_NETOBJ)
-/* #define NLM4_owner_sz               1+XDR_QUADLEN(NLM4_MAXOWNER) */
+#define NLM4_caller_sz         1+XDR_QUADLEN(NLMCLNT_OHSIZE)
+#define NLM4_owner_sz          1+XDR_QUADLEN(NLMCLNT_OHSIZE)
 #define NLM4_fhandle_sz                1+XDR_QUADLEN(NFS3_FHSIZE)
-#define NLM4_lock_sz           5+NLM4_caller_sz+NLM4_netobj_sz+NLM4_fhandle_sz
-#define NLM4_holder_sz         6+NLM4_netobj_sz
+#define NLM4_lock_sz           5+NLM4_caller_sz+NLM4_owner_sz+NLM4_fhandle_sz
+#define NLM4_holder_sz         6+NLM4_owner_sz
 
 #define NLM4_testargs_sz       NLM4_cookie_sz+1+NLM4_lock_sz
 #define NLM4_lockargs_sz       NLM4_cookie_sz+4+NLM4_lock_sz

diff --git a/include/linux/lockd/lockd.h b/include/linux/lockd/lockd.h
index ac25b5649c594a65589ec25f8079a9642333e447..f6a81e0b1b9325c196cdd10c26b4826eff6f251c 100644 (file)
--- a/include/linux/lockd/lockd.h
+++ b/include/linux/lockd/lockd.h
@@ -88,7 +88,7 @@ struct nlm_wait;
 /*
  * Memory chunk for NLM client RPC request.
  */
-#define NLMCLNT_OHSIZE         (sizeof(utsname()->nodename)+10)
+#define NLMCLNT_OHSIZE         ((__NEW_UTS_LEN) + 10u)
 struct nlm_rqst {
        unsigned int            a_flags;        /* initial RPC task flags */
        struct nlm_host *       a_host;         /* host handle */