CVE-2026-80737 in Linux
Summary
by MITRE • 09/03/2026
In the Linux kernel, the following vulnerability has been resolved:
serial: amba-pl011: synchronize DMA teardown
dmaengine_terminate_all() does not wait for a running callback, so the TX callback can still touch the TX buffer after it is freed. The RX poll timer reads the RX buffers without the port lock.
Switch to dmaengine_terminate_sync() and delete the RX timer before freeing the buffers.
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Analysis
by VulDB Data Team • 09/03/2026
The Linux kernel driver for the ARM PrimeCell PL011 UART serial interface contains a concurrency flaw related to the handling of Direct Memory Access operations during device teardown. This vulnerability arises from an improper synchronization mechanism when terminating DMA transfers, which can lead to use-after-free conditions and race conditions that compromise system stability and potentially allow for unauthorized memory access or denial of service attacks against the operating system.
The core technical issue stems from the usage of dmaengine_terminate_all() during the cleanup phase of the driver. This function initiates the termination of DMA transactions but does not guarantee that any currently executing callback functions have completed their execution before returning control to the caller. Consequently, if a transmit buffer is freed immediately after calling this function, there remains a window where the hardware or its associated interrupt handler may still attempt to access that memory region via an outstanding TX callback. This creates a classic use-after-free scenario where kernel code accesses deallocated memory, leading to undefined behavior such as data corruption, system crashes, or potential exploitation by local attackers who can trigger rapid device open and close cycles.
Additionally, the receive path exhibits a separate but related race condition involving polling timers. The RX poll timer is configured to read from RX buffers independently of the main port lock that protects other serial operations. When the driver proceeds to free these buffers without first disabling or deleting this timer, there is a risk that the timer callback will execute concurrently with buffer deallocation. This lack of synchronization means the kernel may attempt to process data in memory regions that are no longer validly mapped or owned by the driver, further exacerbating the stability risks and expanding the attack surface for potential privilege escalation if an attacker can manipulate timing conditions to exploit these race windows.
To resolve this vulnerability, the fix involves switching from dmaengine_terminate_all() to dmaengine_terminate_sync(). The synchronous variant ensures that all pending DMA transactions are fully completed and their callbacks have finished executing before the function returns, thereby eliminating the window for use-after-free access on TX buffers. Furthermore, the remediation includes explicitly deleting the RX poll timer prior to freeing any associated memory resources. This guarantees that no asynchronous read operations can occur against deallocated buffer space, effectively closing the race condition in the receive path and ensuring safe resource cleanup during device removal or error handling sequences.
From a classification perspective, this vulnerability aligns with CWE-416, Use After Free, due to the potential access of freed memory via DMA callbacks, and CWE-362, Concurrent Execution using Shared Resource with Improper Synchronization, regarding the race condition in the RX poll timer logic. In terms of adversarial tactics, this flaw could be leveraged within MITRE ATT&CK technique T1059, Command and Scripting Interpreter, or more broadly under privilege escalation vectors if an attacker can trigger kernel panics to facilitate denial-of-service attacks against critical infrastructure services relying on serial console access.
Mitigation strategies primarily involve applying the upstream Linux kernel patch that implements these synchronization improvements. System administrators should ensure their systems are updated with a kernel version containing this fix, particularly for embedded devices or servers utilizing ARM-based SoCs with PL011 UART controllers. For environments where immediate patching is not feasible, monitoring system logs for serial port errors and restricting physical access to console ports can reduce the risk of exploitation by local users attempting to trigger rapid device state changes.