CVE-2026-23207 in Linux
Summary
by MITRE • 02/14/2026
In the Linux kernel, the following vulnerability has been resolved:
spi: tegra210-quad: Protect curr_xfer check in IRQ handler
Now that all other accesses to curr_xfer are done under the lock, protect the curr_xfer NULL check in tegra_qspi_isr_thread() with the spinlock. Without this protection, the following race can occur:
CPU0 (ISR thread) CPU1 (timeout path) ---------------- ------------------- if (!tqspi->curr_xfer) // sees non-NULL spin_lock() tqspi->curr_xfer = NULL spin_unlock() handle_*_xfer() spin_lock() t = tqspi->curr_xfer // NULL! ... t->len ... // NULL dereference!
With this patch, all curr_xfer accesses are now properly synchronized.
Although all accesses to curr_xfer are done under the lock, in tegra_qspi_isr_thread() it checks for NULL, releases the lock and reacquires it later in handle_cpu_based_xfer()/handle_dma_based_xfer(). There is a potential for an update in between, which could cause a NULL pointer dereference.
To handle this, add a NULL check inside the handlers after acquiring the lock. This ensures that if the timeout path has already cleared curr_xfer, the handler will safely return without dereferencing the NULL pointer.
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Analysis
by VulDB Data Team • 05/24/2026
The vulnerability identified as CVE-2026-23207 resides within the Linux kernel's Tegra SPI driver implementation, specifically affecting the tegra210-quad SPI controller. This issue manifests as a race condition that can lead to a null pointer dereference during interrupt handling operations. The flaw occurs in the tegra_qspi_isr_thread() function where the driver performs a check against the curr_xfer pointer without proper synchronization, creating a window of opportunity for concurrent access violations. The vulnerability is particularly concerning as it affects the interrupt service routine execution path, which is critical for device communication and system stability.
The technical root cause stems from improper synchronization mechanisms within the SPI driver's interrupt handling code. While the driver correctly employs spinlocks to protect most accesses to the curr_xfer pointer, the specific check performed in the interrupt service thread creates a synchronization gap. During normal operation, CPU0 executes the interrupt handler and performs a null check on curr_xfer, but before it can complete the transfer handling, CPU1 may execute the timeout path which sets curr_xfer to NULL. This creates a temporal inconsistency where the interrupt handler observes a non-null value initially but encounters a null pointer when attempting to access the transfer structure. This race condition is classified as a classic concurrent access violation pattern that violates the fundamental principles of proper locking mechanisms.
The operational impact of this vulnerability extends beyond simple system instability to potentially compromise the entire system's reliability and security posture. When a null pointer dereference occurs in kernel space, it typically results in system crashes, kernel oops, or more critically, allows for potential privilege escalation attacks. The vulnerability affects systems utilizing Tegra-based hardware platforms that rely on the quad SPI controller for device communication, potentially impacting embedded systems, automotive platforms, and mobile devices. This flaw represents a significant concern for systems where SPI communication is critical for security-sensitive operations, as it could enable malicious actors to cause denial of service or potentially gain unauthorized access to system resources.
Mitigation strategies for this vulnerability require careful implementation of proper locking mechanisms throughout the interrupt handling path. The solution involves adding additional null checks within the transfer handling functions after acquiring the spinlock, ensuring that even if the timeout path has cleared the curr_xfer pointer, the handler will gracefully return without attempting to dereference a null pointer. This approach aligns with the principle of defensive programming and follows the established security practices outlined in various cybersecurity frameworks. The fix demonstrates proper adherence to the Common Weakness Enumeration standards where race conditions are mitigated through appropriate synchronization primitives. Organizations should prioritize applying this patch to all affected systems and consider implementing additional monitoring for system stability indicators, particularly in environments where SPI-based communication is critical for operational continuity and security enforcement.