!1676 [sync] PR-1596: ksmbd: fix out-of-bound read in deassemble_neg_contexts()

Merge Pull Request from: @openeuler-sync-bot 
 

Origin pull request: 
https://gitee.com/openeuler/kernel/pulls/1596 
 
PR sync from: Li Lingfeng <lilingfeng3@huawei.com>
https://mailweb.openeuler.org/hyperkitty/list/kernel@openeuler.org/message/MKD6POKWLXC45KXPZXCZ7N52MPOZMNAR/ 
 
https://gitee.com/src-openeuler/kernel/issues/I7LU2Q 
 
Link:https://gitee.com/openeuler/kernel/pulls/1676 

Reviewed-by: Jialin Zhang <zhangjialin11@huawei.com> 
Signed-off-by: Jialin Zhang <zhangjialin11@huawei.com> 

fs/ksmbd/smb2pdu.c

@@ -978,13 +978,13 @@ static void decode_sign_cap_ctxt(struct ksmbd_conn *conn,
 
 static __le32 deassemble_neg_contexts(struct ksmbd_conn *conn,
 				      struct smb2_negotiate_req *req,
-				      int len_of_smb)
+				      unsigned int len_of_smb)
 {
 	/* +4 is to account for the RFC1001 len field */
 	struct smb2_neg_context *pctx = (struct smb2_neg_context *)req;
 	int i = 0, len_of_ctxts;
-	int offset = le32_to_cpu(req->NegotiateContextOffset);
-	int neg_ctxt_cnt = le16_to_cpu(req->NegotiateContextCount);
+	unsigned int offset = le32_to_cpu(req->NegotiateContextOffset);
+	unsigned int neg_ctxt_cnt = le16_to_cpu(req->NegotiateContextCount);
 	__le32 status = STATUS_INVALID_PARAMETER;
 
 	ksmbd_debug(SMB, "decoding %d negotiate contexts\n", neg_ctxt_cnt);
@@ -1002,7 +1002,7 @@ static __le32 deassemble_neg_contexts(struct ksmbd_conn *conn,
 		if (len_of_ctxts == 0)
 			break;
 
-		if (len_of_ctxts < sizeof(struct smb2_neg_context))
+		if (len_of_ctxts < (int)sizeof(struct smb2_neg_context))
 			break;
 
 		pctx = (struct smb2_neg_context *)((char *)pctx + offset);
@@ -1053,9 +1053,8 @@ static __le32 deassemble_neg_contexts(struct ksmbd_conn *conn,
 		}
 
 		/* offsets must be 8 byte aligned */
-		clen = (clen + 7) & ~0x7;
-		offset = clen + sizeof(struct smb2_neg_context);
-		len_of_ctxts -= clen + sizeof(struct smb2_neg_context);
+		offset = (clen + sizeof(struct smb2_neg_context) + 7) & ~0x7;
+		len_of_ctxts -= offset;
 	}
 	return status;
 }