Shrink stack space usage in cifs_construct_tcon

We were reserving MAX_USERNAME (now 256) on stack for
something which only needs to fit about 24 bytes ie
string krb50x +  printf version of uid

Signed-off-by: Steve French <sfrench@us.ibm.com>

2 files changed, 5 insertions, 2 deletions

diff --git a/fs/cifs/cifsglob.h b/fs/cifs/cifsglob.h
index 6e211b67b273..108a1e99aa9f 100644
--- a/fs/cifs/cifsglob.h
+++ b/fs/cifs/cifsglob.h
@@ -274,7 +274,8 @@ struct cifsSesInfo {
         int capabilities;
         char serverName[SERVER_NAME_LEN_WITH_NULL * 2]; /* BB make bigger for
                                 TCP names - will ipv6 and sctp addresses fit? */
-        char *user_name;
+        char *user_name;        /* must not be null except during init of sess
+                                   and after mount option parsing we fill it */
         char *domainName;
         char *password;
         struct session_key auth_key;
diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
index 68b7dbf24b92..8d72acbd5c13 100644
--- a/fs/cifs/connect.c
+++ b/fs/cifs/connect.c
@@ -3258,7 +3258,9 @@ cifs_construct_tcon(struct cifs_sb_info *cifs_sb, uid_t fsuid)
         struct cifsSesInfo *ses;
         struct cifsTconInfo *tcon = NULL;
         struct smb_vol *vol_info;
-        char username[MAX_USERNAME_SIZE + 1];
+        char username[28]; /* big enough for "krb50x" + hex of ULONG_MAX 6+16 */
+                           /* We used to have this as MAX_USERNAME which is   */
+                           /* way too big now (256 instead of 32) */
 
         vol_info = kzalloc(sizeof(*vol_info), GFP_KERNEL);
         if (vol_info == NULL) {