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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Shyam Prasad N <sprasad@microsoft.com>,
        "Paulo Alcantara (SUSE)" <pc@cjr.nz>,
        Steve French <stfrench@microsoft.com>
Subject: [PATCH 5.18 175/181] smb3: fix empty netname context on secondary channels
Date:   Mon, 27 Jun 2022 13:22:28 +0200
Message-Id: <20220627111949.758271609@linuxfoundation.org>
In-Reply-To: <20220627111944.553492442@linuxfoundation.org>
References: <20220627111944.553492442@linuxfoundation.org>
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From: Steve French <stfrench@microsoft.com>

commit 73130a7b1ac92c9f30e0a255951129f4851c5794 upstream.

Some servers do not allow null netname contexts, which would cause
multichannel to revert to single channel when mounting to some
servers (e.g. Azure xSMB).

Fixes: 4c14d7043fede ("cifs: populate empty hostnames for extra channels")
Reviewed-by: Shyam Prasad N <sprasad@microsoft.com>
Reviewed-by: Paulo Alcantara (SUSE) <pc@cjr.nz>
Signed-off-by: Steve French <stfrench@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 fs/cifs/smb2pdu.c |   14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

--- a/fs/cifs/smb2pdu.c
+++ b/fs/cifs/smb2pdu.c
@@ -570,16 +570,18 @@ assemble_neg_contexts(struct smb2_negoti
 	*total_len += ctxt_len;
 	pneg_ctxt += ctxt_len;
 
-	ctxt_len = build_netname_ctxt((struct smb2_netname_neg_context *)pneg_ctxt,
-					server->hostname);
-	*total_len += ctxt_len;
-	pneg_ctxt += ctxt_len;
-
 	build_posix_ctxt((struct smb2_posix_neg_context *)pneg_ctxt);
 	*total_len += sizeof(struct smb2_posix_neg_context);
 	pneg_ctxt += sizeof(struct smb2_posix_neg_context);
 
-	neg_context_count = 4;
+	if (server->hostname && (server->hostname[0] != 0)) {
+		ctxt_len = build_netname_ctxt((struct smb2_netname_neg_context *)pneg_ctxt,
+					server->hostname);
+		*total_len += ctxt_len;
+		pneg_ctxt += ctxt_len;
+		neg_context_count = 4;
+	} else /* second channels do not have a hostname */
+		neg_context_count = 3;
 
 	if (server->compress_algorithm) {
 		build_compression_ctxt((struct smb2_compression_capabilities_context *)