linux-kernel - [PATCH 5.12 331/384] smb3: do not attempt multichannel to server which does not support it

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Date:   Mon, 10 May 2021 12:22:00 +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, Shyam Prasad N <sprasad@...rosoft.com>,
        Tom Talpey <tom@...pey.com>,
        Steve French <stfrench@...rosoft.com>
Subject: [PATCH 5.12 331/384] smb3: do not attempt multichannel to server which does not support it

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

commit 9c2dc11df50d1c8537075ff6b98472198e24438e upstream.

We were ignoring CAP_MULTI_CHANNEL in the server response - if the
server doesn't support multichannel we should not be attempting it.

See MS-SMB2 section 3.2.5.2

Reviewed-by: Shyam Prasad N <sprasad@...rosoft.com>
Reviewed-By: Tom Talpey <tom@...pey.com>
Cc: <stable@...r.kernel.org> # v5.8+
Signed-off-by: Steve French <stfrench@...rosoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 fs/cifs/sess.c |    6 ++++++
 1 file changed, 6 insertions(+)

--- a/fs/cifs/sess.c
+++ b/fs/cifs/sess.c
@@ -97,6 +97,12 @@ int cifs_try_adding_channels(struct cifs
 		return 0;
 	}
 
+	if (!(ses->server->capabilities & SMB2_GLOBAL_CAP_MULTI_CHANNEL)) {
+		cifs_dbg(VFS, "server %s does not support multichannel\n", ses->server->hostname);
+		ses->chan_max = 1;
+		return 0;
+	}
+
 	/*
 	 * Make a copy of the iface list at the time and use that
 	 * instead so as to not hold the iface spinlock for opening