1 files changed, 56 insertions, 1 deletions

diff --git a/fs/cifs/sess.c b/fs/cifs/sess.c
index 82b784a62c16..79358e341fd2 100644
--- a/fs/cifs/sess.c
+++ b/fs/cifs/sess.c
@@ -550,6 +550,56 @@ setup_ntlmv2_ret:
         return rc;
 }
 
+enum securityEnum
+select_sectype(struct TCP_Server_Info *server, enum securityEnum requested)
+{
+        switch (server->negflavor) {
+        case CIFS_NEGFLAVOR_EXTENDED:
+                switch (requested) {
+                case Kerberos:
+                case RawNTLMSSP:
+                        return requested;
+                case Unspecified:
+                        if (server->sec_ntlmssp &&
+                            (global_secflags & CIFSSEC_MAY_NTLMSSP))
+                                return RawNTLMSSP;
+                        if ((server->sec_kerberos || server->sec_mskerberos) &&
+                            (global_secflags & CIFSSEC_MAY_KRB5))
+                                return Kerberos;
+                        /* Fallthrough */
+                default:
+                        return Unspecified;
+                }
+        case CIFS_NEGFLAVOR_UNENCAP:
+                switch (requested) {
+                case NTLM:
+                case NTLMv2:
+                        return requested;
+                case Unspecified:
+                        if (global_secflags & CIFSSEC_MAY_NTLMV2)
+                                return NTLMv2;
+                        if (global_secflags & CIFSSEC_MAY_NTLM)
+                                return NTLM;
+                        /* Fallthrough */
+                default:
+                        return Unspecified;
+                }
+        case CIFS_NEGFLAVOR_LANMAN:
+                switch (requested) {
+                case LANMAN:
+                        return requested;
+                case Unspecified:
+                        if (global_secflags & CIFSSEC_MAY_LANMAN)
+                                return LANMAN;
+                        /* Fallthrough */
+                default:
+                        return Unspecified;
+                }
+        default:
+                return Unspecified;
+        }
+}
+
 int
 CIFS_SessSetup(const unsigned int xid, struct cifs_ses *ses,
                const struct nls_table *nls_cp)
@@ -576,8 +626,13 @@ CIFS_SessSetup(const unsigned int xid, struct cifs_ses *ses,
                 return -EINVAL;
         }
 
-        type = ses->server->secType;
+        type = select_sectype(ses->server, ses->sectype);
         cifs_dbg(FYI, "sess setup type %d\n", type);
+        if (type == Unspecified) {
+                cifs_dbg(VFS, "Unable to select appropriate authentication method!");
+                return -EINVAL;
+        }
+
         if (type == RawNTLMSSP) {
                 /* if memory allocation is successful, caller of this function
                  * frees it.