CVE-2024-41088 - Loop with Unreachable Exit Condition ('Infinite Loop')

Severity

55%

Complexity

18%

Confidentiality

60%

In the Linux kernel, the following vulnerability has been resolved: can: mcp251xfd: fix infinite loop when xmit fails When the mcp251xfd_start_xmit() function fails, the driver stops processing messages, and the interrupt routine does not return, running indefinitely even after killing the running application. Error messages: [ 441.298819] mcp251xfd spi2.0 can0: ERROR in mcp251xfd_start_xmit: -16 [ 441.306498] mcp251xfd spi2.0 can0: Transmit Event FIFO buffer not empty. (seq=0x000017c7, tef_tail=0x000017cf, tef_head=0x000017d0, tx_head=0x000017d3). ... and repeat forever. The issue can be triggered when multiple devices share the same SPI interface. And there is concurrent access to the bus. The problem occurs because tx_ring->head increments even if mcp251xfd_start_xmit() fails. Consequently, the driver skips one TX package while still expecting a response in mcp251xfd_handle_tefif_one(). Resolve the issue by starting a workqueue to write the tx obj synchronously if err = -EBUSY. In case of another error, decrement tx_ring->head, remove skb from the echo stack, and drop the message. [mkl: use more imperative wording in patch description]

CVSS 3.1 Base Score 5.5. CVSS Attack Vector: local. CVSS Attack Complexity: low. CVSS Vector: (CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H).

Demo Examples

Loop with Unreachable Exit Condition ('Infinite Loop')

CWE-835

In the following code the method processMessagesFromServer attempts to establish a connection to a server and read and process messages from the server. The method uses a do/while loop to continue trying to establish the connection to the server when an attempt fails.


               
}
...// create socket to connect to server
}// establish connection to server// if connected then read and process messages from server
...// read and process messages
// keep trying to establish connection to the server// close socket and return success or failure

However, this will create an infinite loop if the server does not respond. This infinite loop will consume system resources and can be used to create a denial of service attack. To resolve this a counter should be used to limit the number of attempts to establish a connection to the server, as in the following code.


               
}
...// initialize number of attempts counter
}// establish connection to server// increment counter// if connected then read and process messages from server
...// read and process messages
// keep trying to establish connection to the server// up to a maximum number of attempts// close socket and return success or failure

Loop with Unreachable Exit Condition ('Infinite Loop')

CWE-835

For this example the method isReorderNeeded as part of a bookstore application that determines if a particular book needs to be reordered based on the current inventory count and the rate at which the book is being sold.


               
}
return isReorder;// get inventory count for book// find number of days until inventory count reaches minimum
days++;
// if number of days within reorder timeframe// set reorder return boolean to true
isReorder = true;

However, the while loop will become an infinite loop if the rateSold input parameter has a value of zero since the inventoryCount will never fall below the minimumCount. In this case the input parameter should be validated to ensure that a value of zero does not cause an infinite loop,as in the following code.


               
}
...// validate rateSold variable
return isReorder;

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