cifs: fix credit accounting for extra channel

commit a249cc8 upstream.

With multichannel, operations like the queries
from "ls -lR" can cause all credits to be used and
errors to be returned since max_credits was not
being set correctly on the secondary channels and
thus the client was requesting 0 credits incorrectly
in some cases (which can lead to not having
enough credits to perform any operation on that
channel).

Signed-off-by: Aurelien Aptel <aaptel@suse.com>
CC: <stable@vger.kernel.org> # v5.8+
Reviewed-by: Shyam Prasad N <sprasad@microsoft.com>
Signed-off-by: Steve French <stfrench@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

fs/cifs/connect.c

@@ -1405,6 +1405,11 @@ cifs_get_tcp_session(struct smb3_fs_context *ctx)
 	tcp_ses->min_offload = ctx->min_offload;
 	tcp_ses->tcpStatus = CifsNeedNegotiate;
 
+	if ((ctx->max_credits < 20) || (ctx->max_credits > 60000))
+		tcp_ses->max_credits = SMB2_MAX_CREDITS_AVAILABLE;
+	else
+		tcp_ses->max_credits = ctx->max_credits;
+
 	tcp_ses->nr_targets = 1;
 	tcp_ses->ignore_signature = ctx->ignore_signature;
 	/* thread spawned, put it on the list */
@@ -2806,11 +2811,6 @@ static int mount_get_conns(struct smb3_fs_context *ctx, struct cifs_sb_info *cif
 
 	*nserver = server;
 
-	if ((ctx->max_credits < 20) || (ctx->max_credits > 60000))
-		server->max_credits = SMB2_MAX_CREDITS_AVAILABLE;
-	else
-		server->max_credits = ctx->max_credits;
-
 	/* get a reference to a SMB session */
 	ses = cifs_get_smb_ses(server, ctx);
 	if (IS_ERR(ses)) {

fs/cifs/sess.c

@@ -230,6 +230,7 @@ cifs_ses_add_channel(struct cifs_sb_info *cifs_sb, struct cifs_ses *ses,
 	ctx.noautotune = ses->server->noautotune;
 	ctx.sockopt_tcp_nodelay = ses->server->tcp_nodelay;
 	ctx.echo_interval = ses->server->echo_interval / HZ;
+	ctx.max_credits = ses->server->max_credits;
 
 	/*
 	 * This will be used for encoding/decoding user/domain/pw