linux-kernel - [PATCH 5.18 133/231] smb3: workaround negprot bug in some Samba servers

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Date:   Tue, 19 Jul 2022 13:53:38 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Julian Sikorski <belegdol@...il.com>,
        Julian Sikorski <belegdol+github@...il.com>,
        Shyam Prasad N <sprasad@...rosoft.com>,
        Steve French <stfrench@...rosoft.com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.18 133/231] smb3: workaround negprot bug in some Samba servers

From: Steve French <stfrench@...rosoft.com>

[ Upstream commit 32f319183c439b239294cb2d70ada3564c4c7c39 ]

Mount can now fail to older Samba servers due to a server
bug handling padding at the end of the last negotiate
context (negotiate contexts typically are rounded up to 8
bytes by adding padding if needed). This server bug can
be avoided by switching the order of negotiate contexts,
placing a negotiate context at the end that does not
require padding (prior to the recent netname context fix
this was the case on the client).

Fixes: 73130a7b1ac9 ("smb3: fix empty netname context on secondary channels")
Reported-by: Julian Sikorski <belegdol@...il.com>
Tested-by: Julian Sikorski <belegdol+github@...il.com>
Reviewed-by: Shyam Prasad N <sprasad@...rosoft.com>
Signed-off-by: Steve French <stfrench@...rosoft.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 fs/cifs/smb2pdu.c | 13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/fs/cifs/smb2pdu.c b/fs/cifs/smb2pdu.c
index 6a8a00f28b19..2e6c0f4d8449 100644
--- a/fs/cifs/smb2pdu.c
+++ b/fs/cifs/smb2pdu.c
@@ -571,10 +571,6 @@ assemble_neg_contexts(struct smb2_negotiate_req *req,
 	*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);
-
 	/*
 	 * secondary channels don't have the hostname field populated
 	 * use the hostname field in the primary channel instead
@@ -586,9 +582,14 @@ assemble_neg_contexts(struct smb2_negotiate_req *req,
 					      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;
+	} else
+		neg_context_count = 2;
+
+	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++;
 
 	if (server->compress_algorithm) {
 		build_compression_ctxt((struct smb2_compression_capabilities_context *)
-- 
2.35.1