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[82.51.6.75]) by smtp.gmail.com with ESMTPSA id w10sm34795307wra.34.2020.11.18.06.37.42 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 18 Nov 2020 06:37:43 -0800 (PST) From: "Andrea Parri (Microsoft)" To: linux-kernel@vger.kernel.org Cc: "K . Y . Srinivasan" , Haiyang Zhang , Stephen Hemminger , Wei Liu , linux-hyperv@vger.kernel.org, Michael Kelley , Juan Vazquez , Saruhan Karademir , "Andrea Parri (Microsoft)" Subject: [PATCH 3/6] Drivers: hv: vmbus: Avoid double fetch of payload_size in vmbus_on_msg_dpc() Date: Wed, 18 Nov 2020 15:36:46 +0100 Message-Id: <20201118143649.108465-4-parri.andrea@gmail.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20201118143649.108465-1-parri.andrea@gmail.com> References: <20201118143649.108465-1-parri.andrea@gmail.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-hyperv@vger.kernel.org vmbus_on_msg_dpc() double fetches from payload_size. The double fetch can lead to a buffer overflow when (mem)copying the hv_message object. Avoid the double fetch by saving the value of payload_size into a local variable. Reported-by: Juan Vazquez Signed-off-by: Andrea Parri (Microsoft) --- drivers/hv/vmbus_drv.c | 17 +++++++---------- 1 file changed, 7 insertions(+), 10 deletions(-) diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c index 82b23baa446d7..0e39f1d6182e9 100644 --- a/drivers/hv/vmbus_drv.c +++ b/drivers/hv/vmbus_drv.c @@ -1056,6 +1056,7 @@ void vmbus_on_msg_dpc(unsigned long data) void *page_addr = hv_cpu->synic_message_page; struct hv_message *msg = (struct hv_message *)page_addr + VMBUS_MESSAGE_SINT; + __u8 payload_size = msg->header.payload_size; struct vmbus_channel_message_header *hdr; enum vmbus_channel_message_type msgtype; const struct vmbus_channel_message_table_entry *entry; @@ -1089,9 +1090,8 @@ void vmbus_on_msg_dpc(unsigned long data) goto msg_handled; } - if (msg->header.payload_size > HV_MESSAGE_PAYLOAD_BYTE_COUNT) { - WARN_ONCE(1, "payload size is too large (%d)\n", - msg->header.payload_size); + if (payload_size > HV_MESSAGE_PAYLOAD_BYTE_COUNT) { + WARN_ONCE(1, "payload size is too large (%d)\n", payload_size); goto msg_handled; } @@ -1100,21 +1100,18 @@ void vmbus_on_msg_dpc(unsigned long data) if (!entry->message_handler) goto msg_handled; - if (msg->header.payload_size < entry->min_payload_len) { - WARN_ONCE(1, "message too short: msgtype=%d len=%d\n", - msgtype, msg->header.payload_size); + if (payload_size < entry->min_payload_len) { + WARN_ONCE(1, "message too short: msgtype=%d len=%d\n", msgtype, payload_size); goto msg_handled; } if (entry->handler_type == VMHT_BLOCKING) { - ctx = kmalloc(sizeof(*ctx) + msg->header.payload_size, - GFP_ATOMIC); + ctx = kmalloc(sizeof(*ctx) + payload_size, GFP_ATOMIC); if (ctx == NULL) return; INIT_WORK(&ctx->work, vmbus_onmessage_work); - memcpy(&ctx->msg, msg, sizeof(msg->header) + - msg->header.payload_size); + memcpy(&ctx->msg, msg, sizeof(msg->header) + payload_size); /* * The host can generate a rescind message while we -- 2.25.1