nfs: Fix showing truncated fsid/dev in, /proc/net/nfsfs/volumes

A truncated fsid showing from /proc/fs/nfsfs/volumes as,
NV SERVER   PORT DEV     FSID              FSC
v4 c0a80881  801 0:43    34931f044c2a439b  no

It should be as,
NV SERVER   PORT DEV          FSID                              FSC
v4 c0a80881  801 0:43         34931f044c2a439b:954c5d830fa4be8c no

The max buffer length for storing "%llx:%llx" format should be
 16 + 1 + 16 + 1 = 34 (16 for %llx, 1 for ':', 1 for '\0').

Also, for storing "%u:%u" of MAJOR() and MINOR() should be
 8 + 1 + 3 + 1 = 13 (8 for 2^24, 1 for ':', 3 for 2^8, 1 for '\0').

v2, add comments for dev/fsid buffer and use sizeof in snprintf.

Signed-off-by: Kinglong Mee <kinglongmee@gmail.com>
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>

1 files changed, 7 insertions, 5 deletions

diff --git a/fs/nfs/client.c b/fs/nfs/client.c
index 892aefff3630..1e37491904ee 100644
--- a/fs/nfs/client.c
+++ b/fs/nfs/client.c
@@ -1364,27 +1364,29 @@ static int nfs_volume_list_show(struct seq_file *m, void *v)
 {
         struct nfs_server *server;
         struct nfs_client *clp;
-        char dev[8], fsid[17];
+        char dev[13];   // 8 for 2^24, 1 for ':', 3 for 2^8, 1 for '\0'
+        char fsid[34];  // 2 * 16 for %llx, 1 for ':', 1 for '\0'
         struct nfs_net *nn = net_generic(seq_file_net(m), nfs_net_id);
 
         /* display header on line 1 */
         if (v == &nn->nfs_volume_list) {
-                seq_puts(m, "NV SERVER   PORT DEV     FSID              FSC\n");
+                seq_puts(m, "NV SERVER   PORT DEV          FSID"
+                            "                              FSC\n");
                 return 0;
         }
         /* display one transport per line on subsequent lines */
         server = list_entry(v, struct nfs_server, master_link);
         clp = server->nfs_client;
 
-        snprintf(dev, 8, "%u:%u",
+        snprintf(dev, sizeof(dev), "%u:%u",
                  MAJOR(server->s_dev), MINOR(server->s_dev));
 
-        snprintf(fsid, 17, "%llx:%llx",
+        snprintf(fsid, sizeof(fsid), "%llx:%llx",
                  (unsigned long long) server->fsid.major,
                  (unsigned long long) server->fsid.minor);
 
         rcu_read_lock();
-        seq_printf(m, "v%u %s %s %-7s %-17s %s\n",
+        seq_printf(m, "v%u %s %s %-12s %-33s %s\n",
                    clp->rpc_ops->version,
                    rpc_peeraddr2str(clp->cl_rpcclient, RPC_DISPLAY_HEX_ADDR),
                    rpc_peeraddr2str(clp->cl_rpcclient, RPC_DISPLAY_HEX_PORT),