[PATCH v2 1/2] NFSv4: Clean up initialisation of uniquified client id strings

[trondmy@kernel.org]

From: Trond Myklebust <trond.myklebust@hammerspace.com>

When the user sets a uniquifier, then ensure we copy the string
so that calls to strlen() etc are atomic with calls to snprintf().

Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
---
 fs/nfs/nfs4proc.c | 75 +++++++++++++++++++++--------------------------
 1 file changed, 34 insertions(+), 41 deletions(-)

diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
index 6e95c85fe395..da12b22508a8 100644
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -6006,9 +6006,22 @@ static void nfs4_init_boot_verifier(const struct nfs_client *clp,
 	memcpy(bootverf->data, verf, sizeof(bootverf->data));
 }
 
+static size_t
+nfs4_get_uniquifier(char *buf, size_t buflen)
+{
+	buf[0] = '\0';
+
+	if (nfs4_client_id_uniquifier[0] != '\0')
+		strscpy(buf, nfs4_client_id_uniquifier, buflen);
+
+	return strlen(buf);
+}
+
 static int
 nfs4_init_nonuniform_client_string(struct nfs_client *clp)
 {
+	char buf[NFS4_CLIENT_ID_UNIQ_LEN];
+	size_t buflen;
 	size_t len;
 	char *str;
 
@@ -6022,8 +6035,11 @@ nfs4_init_nonuniform_client_string(struct nfs_client *clp)
 		strlen(rpc_peeraddr2str(clp->cl_rpcclient, RPC_DISPLAY_ADDR)) +
 		1;
 	rcu_read_unlock();
-	if (nfs4_client_id_uniquifier[0] != '\0')
-		len += strlen(nfs4_client_id_uniquifier) + 1;
+
+	buflen = nfs4_get_uniquifier(buf, sizeof(buf));
+	if (buflen)
+		len += buflen + 1;
+
 	if (len > NFS4_OPAQUE_LIMIT + 1)
 		return -EINVAL;
 
@@ -6037,10 +6053,9 @@ nfs4_init_nonuniform_client_string(struct nfs_client *clp)
 		return -ENOMEM;
 
 	rcu_read_lock();
-	if (nfs4_client_id_uniquifier[0] != '\0')
+	if (buflen)
 		scnprintf(str, len, "Linux NFSv4.0 %s/%s/%s",
-			  clp->cl_rpcclient->cl_nodename,
-			  nfs4_client_id_uniquifier,
+			  clp->cl_rpcclient->cl_nodename, buf,
 			  rpc_peeraddr2str(clp->cl_rpcclient,
 					   RPC_DISPLAY_ADDR));
 	else
@@ -6054,51 +6069,24 @@ nfs4_init_nonuniform_client_string(struct nfs_client *clp)
 	return 0;
 }
 
-static int
-nfs4_init_uniquifier_client_string(struct nfs_client *clp)
-{
-	size_t len;
-	char *str;
-
-	len = 10 + 10 + 1 + 10 + 1 +
-		strlen(nfs4_client_id_uniquifier) + 1 +
-		strlen(clp->cl_rpcclient->cl_nodename) + 1;
-
-	if (len > NFS4_OPAQUE_LIMIT + 1)
-		return -EINVAL;
-
-	/*
-	 * Since this string is allocated at mount time, and held until the
-	 * nfs_client is destroyed, we can use GFP_KERNEL here w/o worrying
-	 * about a memory-reclaim deadlock.
-	 */
-	str = kmalloc(len, GFP_KERNEL);
-	if (!str)
-		return -ENOMEM;
-
-	scnprintf(str, len, "Linux NFSv%u.%u %s/%s",
-			clp->rpc_ops->version, clp->cl_minorversion,
-			nfs4_client_id_uniquifier,
-			clp->cl_rpcclient->cl_nodename);
-	clp->cl_owner_id = str;
-	return 0;
-}
-
 static int
 nfs4_init_uniform_client_string(struct nfs_client *clp)
 {
+	char buf[NFS4_CLIENT_ID_UNIQ_LEN];
+	size_t buflen;
 	size_t len;
 	char *str;
 
 	if (clp->cl_owner_id != NULL)
 		return 0;
 
-	if (nfs4_client_id_uniquifier[0] != '\0')
-		return nfs4_init_uniquifier_client_string(clp);
-
 	len = 10 + 10 + 1 + 10 + 1 +
 		strlen(clp->cl_rpcclient->cl_nodename) + 1;
 
+	buflen = nfs4_get_uniquifier(buf, sizeof(buf));
+	if (buflen)
+		len += buflen + 1;
+
 	if (len > NFS4_OPAQUE_LIMIT + 1)
 		return -EINVAL;
 
@@ -6111,9 +6099,14 @@ nfs4_init_uniform_client_string(struct nfs_client *clp)
 	if (!str)
 		return -ENOMEM;
 
-	scnprintf(str, len, "Linux NFSv%u.%u %s",
-			clp->rpc_ops->version, clp->cl_minorversion,
-			clp->cl_rpcclient->cl_nodename);
+	if (buflen)
+		scnprintf(str, len, "Linux NFSv%u.%u %s/%s",
+			  clp->rpc_ops->version, clp->cl_minorversion,
+			  buf, clp->cl_rpcclient->cl_nodename);
+	else
+		scnprintf(str, len, "Linux NFSv%u.%u %s",
+			  clp->rpc_ops->version, clp->cl_minorversion,
+			  clp->cl_rpcclient->cl_nodename);
 	clp->cl_owner_id = str;
 	return 0;
 }
-- 
2.26.2