[CIFS] Fix cifsd so shuts down when signing fails during mount

Fixes two problems:
1) we dropped down to negotiating lanman if we did not recognize the
mechanism (krb5 e.g.)
2) we did not stop cifsd (thus will fail when doing rmod cifs with
slab free errors) when we fail tcon but have a bad session (which is
the case in which signing is required but we don't allow signing on
the client)

It also turns on extended security flag in the header when passing
"sec=krb5" on mount command (although kerberos support is not done of
course)
Acked-by: Jeff Layton <jlayton@redhat.com>
CC: Shaggy <shaggy@us.ibm.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>

fs/cifs/cifs_debug.c

@@ -879,11 +879,16 @@ security_flags_write(struct file *file, const char __user *buffer,
 	if (count < 3) {
 		/* single char or single char followed by null */
 		c = flags_string[0];
-		if (c == '0' || c == 'n' || c == 'N')
+		if (c == '0' || c == 'n' || c == 'N') {
 			extended_security = CIFSSEC_DEF; /* default */
-		else if (c == '1' || c == 'y' || c == 'Y')
+			return count;
+		} else if (c == '1' || c == 'y' || c == 'Y') {
 			extended_security = CIFSSEC_MAX;
 			return count;
+		} else if (!isdigit(c)) {
+			cERROR(1, ("invalid flag %c", c));
+			return -EINVAL;
+		}
 	}
 	/* else we have a number */
 

fs/cifs/cifsglob.h

@@ -90,7 +90,8 @@ enum statusEnum {
 };
 
 enum securityEnum {
-	LANMAN = 0,             /* Legacy LANMAN auth */
+	PLAINTXT = 0, 		/* Legacy with Plaintext passwords */
+	LANMAN,			/* Legacy LANMAN auth */
 	NTLM,			/* Legacy NTLM012 auth with NTLM hash */
 	NTLMv2,			/* Legacy NTLM auth with NTLMv2 hash */
 	RawNTLMSSP,		/* NTLMSSP without SPNEGO */
@@ -499,6 +500,7 @@ require use of the stronger protocol */
 
 #define   CIFSSEC_DEF  CIFSSEC_MAY_SIGN | CIFSSEC_MAY_NTLM | CIFSSEC_MAY_NTLMV2
 #define   CIFSSEC_MAX  CIFSSEC_MUST_SIGN | CIFSSEC_MUST_NTLMV2
+#define   CIFSSEC_AUTH_MASK (CIFSSEC_MAY_NTLM | CIFSSEC_MAY_NTLMV2 | CIFSSEC_MAY_LANMAN | CIFSSEC_MAY_PLNTXT | CIFSSEC_MAY_KRB5)
 /*
  *****************************************************************
  * All constants go here

fs/cifs/cifssmb.c

@@ -438,8 +438,13 @@ CIFSSMBNegotiate(unsigned int xid, struct cifsSesInfo *ses)
 
 	pSMB->hdr.Mid = GetNextMid(server);
 	pSMB->hdr.Flags2 |= (SMBFLG2_UNICODE | SMBFLG2_ERR_STATUS);
+
 	if ((secFlags & CIFSSEC_MUST_KRB5) == CIFSSEC_MUST_KRB5)
 		pSMB->hdr.Flags2 |= SMBFLG2_EXT_SEC;
+	else if ((secFlags & CIFSSEC_AUTH_MASK) == CIFSSEC_MAY_KRB5) {
+		cFYI(1, ("Kerberos only mechanism, enable extended security"));
+		pSMB->hdr.Flags2 |= SMBFLG2_EXT_SEC;
+	}
 
 	count = 0;
 	for (i = 0; i < CIFS_NUM_PROT; i++) {
@@ -573,7 +578,20 @@ CIFSSMBNegotiate(unsigned int xid, struct cifsSesInfo *ses)
 		server->secType = NTLM;
 	else if (secFlags & CIFSSEC_MAY_NTLMV2)
 		server->secType = NTLMv2;
-	/* else krb5 ... any others ... */
+	else if (secFlags & CIFSSEC_MAY_KRB5)
+		server->secType = Kerberos;
+	else if (secFlags & CIFSSEC_MAY_LANMAN)
+		server->secType = LANMAN;
+/* #ifdef CONFIG_CIFS_EXPERIMENTAL
+	else if (secFlags & CIFSSEC_MAY_PLNTXT)
+		server->secType = ??
+#endif */
+	else {
+		rc = -EOPNOTSUPP;
+		cERROR(1, ("Invalid security type"));
+		goto neg_err_exit;
+	}
+	/* else ... any others ...? */
 
 	/* one byte, so no need to convert this or EncryptionKeyLen from
 	   little endian */
@@ -3089,8 +3107,7 @@ CIFSSMBGetCIFSACL(const int xid, struct cifsTconInfo *tcon, __u16 fid,
 			goto qsec_out;
 		pSMBr = (struct smb_com_ntransact_rsp *)iov[0].iov_base;
 
-		cERROR(1, ("smb %p parm %p data %p",
-			  pSMBr, parm, psec_desc));  /* BB removeme BB */
+		cFYI(1, ("smb %p parm %p data %p", pSMBr, parm, psec_desc));
 
 		if (le32_to_cpu(pSMBr->ParameterCount) != 4) {
 			rc = -EIO;      /* bad smb */

fs/cifs/connect.c

@@ -2172,8 +2172,18 @@ cifs_mount(struct super_block *sb, struct cifs_sb_info *cifs_sb,
 						if (tsk)
 							kthread_stop(tsk);
 					}
-				} else
+				} else {
 					cFYI(1, ("No session or bad tcon"));
+					if ((pSesInfo->server) &&
+					    (pSesInfo->server->tsk)) {
+						struct task_struct *tsk;
+						force_sig(SIGKILL,
+							pSesInfo->server->tsk);
+						tsk = pSesInfo->server->tsk;
+						if (tsk)
+							kthread_stop(tsk);
+					}
+				}
 				sesInfoFree(pSesInfo);
 				/* pSesInfo = NULL; */
 			}