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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, Namjae Jeon <linkinjeon@kernel.org>,
        Steve French <stfrench@microsoft.com>
Subject: [PATCH 5.16 0040/1039] ksmbd: limits exceeding the maximum allowable outstanding requests
Date:   Mon, 24 Jan 2022 19:30:29 +0100
Message-Id: <20220124184126.488263460@linuxfoundation.org>
In-Reply-To: <20220124184125.121143506@linuxfoundation.org>
References: <20220124184125.121143506@linuxfoundation.org>
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From: Namjae Jeon <linkinjeon@kernel.org>

commit b589f5db6d4af8f14d70e31e1276b4c017668a26 upstream.

If the client ignores the CreditResponse received from the server and
continues to send the request, ksmbd limits the requests if it exceeds
smb2 max credits.

Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 fs/ksmbd/connection.c |    1 +
 fs/ksmbd/connection.h |    3 ++-
 fs/ksmbd/smb2misc.c   |    9 +++++++++
 fs/ksmbd/smb2pdu.c    |    1 +
 4 files changed, 13 insertions(+), 1 deletion(-)

--- a/fs/ksmbd/connection.c
+++ b/fs/ksmbd/connection.c
@@ -62,6 +62,7 @@ struct ksmbd_conn *ksmbd_conn_alloc(void
 	atomic_set(&conn->req_running, 0);
 	atomic_set(&conn->r_count, 0);
 	conn->total_credits = 1;
+	conn->outstanding_credits = 1;
 
 	init_waitqueue_head(&conn->req_running_q);
 	INIT_LIST_HEAD(&conn->conns_list);
--- a/fs/ksmbd/connection.h
+++ b/fs/ksmbd/connection.h
@@ -61,7 +61,8 @@ struct ksmbd_conn {
 	atomic_t			req_running;
 	/* References which are made for this Server object*/
 	atomic_t			r_count;
-	unsigned short			total_credits;
+	unsigned int			total_credits;
+	unsigned int			outstanding_credits;
 	spinlock_t			credits_lock;
 	wait_queue_head_t		req_running_q;
 	/* Lock to protect requests list*/
--- a/fs/ksmbd/smb2misc.c
+++ b/fs/ksmbd/smb2misc.c
@@ -337,7 +337,16 @@ static int smb2_validate_credit_charge(s
 			    credit_charge, conn->total_credits);
 		ret = 1;
 	}
+
+	if ((u64)conn->outstanding_credits + credit_charge > conn->vals->max_credits) {
+		ksmbd_debug(SMB, "Limits exceeding the maximum allowable outstanding requests, given : %u, pending : %u\n",
+			    credit_charge, conn->outstanding_credits);
+		ret = 1;
+	} else
+		conn->outstanding_credits += credit_charge;
+
 	spin_unlock(&conn->credits_lock);
+
 	return ret;
 }
 
--- a/fs/ksmbd/smb2pdu.c
+++ b/fs/ksmbd/smb2pdu.c
@@ -322,6 +322,7 @@ int smb2_set_rsp_credits(struct ksmbd_wo
 	}
 
 	conn->total_credits -= credit_charge;
+	conn->outstanding_credits -= credit_charge;
 	credits_requested = max_t(unsigned short,
 				  le16_to_cpu(req_hdr->CreditRequest), 1);