[PATCH 1/2] cifs: allow guest mounts to work for smb3.11

[Tyler Hicks]

From: Ronnie Sahlberg <lsahlber at redhat.com>

BugLink: https://launchpad.net/bugs/1821053

Fix Guest/Anonymous sessions so that they work with SMB 3.11.

The commit noted below tightened the conditions and forced signing for
the SMB2-TreeConnect commands as per MS-SMB2.
However, this should only apply to normal user sessions and not for
Guest/Anonumous sessions.

Fixes: 6188f28bf608 ("Tree connect for SMB3.1.1 must be signed for non-encrypted shares")

Signed-off-by: Ronnie Sahlberg <lsahlber at redhat.com>
CC: Stable <stable at vger.kernel.org>
Signed-off-by: Steve French <stfrench at microsoft.com>
(cherry picked from commit e71ab2aa06f731a944993120b0eef1556c63b81c)
Signed-off-by: Tyler Hicks <tyhicks at canonical.com>
---
 fs/cifs/smb2pdu.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/fs/cifs/smb2pdu.c b/fs/cifs/smb2pdu.c
index 77b3aaa39b35..a68bed9c74a9 100644
--- a/fs/cifs/smb2pdu.c
+++ b/fs/cifs/smb2pdu.c
@@ -1605,9 +1605,13 @@ SMB2_tcon(const unsigned int xid, struct cifs_ses *ses, const char *tree,
 	iov[1].iov_base = unc_path;
 	iov[1].iov_len = unc_path_len;
 
-	/* 3.11 tcon req must be signed if not encrypted. See MS-SMB2 3.2.4.1.1 */
+	/*
+	 * 3.11 tcon req must be signed if not encrypted. See MS-SMB2 3.2.4.1.1
+	 * unless it is guest or anonymous user. See MS-SMB2 3.2.5.3.1
+	 */
 	if ((ses->server->dialect == SMB311_PROT_ID) &&
-	    !smb3_encryption_required(tcon))
+	    !smb3_encryption_required(tcon) &&
+	    !(ses->session_flags & (SMB2_SESSION_FLAG_IS_GUEST|SMB2_SESSION_FLAG_IS_NULL)))
 		req->sync_hdr.Flags |= SMB2_FLAGS_SIGNED;
 
 	memset(&rqst, 0, sizeof(struct smb_rqst));
-- 
2.7.4