CVE-2026-46296 Overview
CVE-2026-46296 affects the Linux kernel's Samsung S3C64xx Serial Peripheral Interface (SPI) controller driver. The flaw causes a NULL pointer dereference when the driver is unbound from a device. A prior refactor moved Direct Memory Access (DMA) channel allocation from probe() into s3c64xx_spi_prepare_transfer() but left the matching deallocation logic inside remove(). When remove() runs without a prior prepare_transfer() call, the driver attempts to release DMA channels that were never allocated, dereferencing a NULL pointer in kernel context.
Critical Impact
Local users with the ability to unbind the s3c64xx SPI driver can trigger a kernel NULL pointer dereference, resulting in a denial of service on affected Linux systems.
Affected Products
- Linux kernel branches containing the s3c64xx SPI driver with the DMA allocation refactor
- Systems using Samsung S3C64xx, S5Pv210, and Exynos SoCs that rely on the spi-s3c64xx driver
- Distributions shipping unpatched stable kernels referenced in the upstream commits
Discovery Timeline
- 2026-06-08 - CVE-2026-46296 published to the National Vulnerability Database (NVD)
- 2026-06-08 - Last updated in NVD database
Technical Details for CVE-2026-46296
Vulnerability Analysis
The spi-s3c64xx driver manages SPI controllers on Samsung-based platforms and uses DMA engines to transfer data between memory and the SPI peripheral. An earlier patch relocated DMA channel acquisition from the device probe() path back to s3c64xx_spi_prepare_transfer(), where channels are requested only when the controller is prepared for a transfer. The corresponding cleanup path in remove() was not updated to match this lifecycle change.
When the driver is unbound through sysfs or during module removal, remove() calls dma_release_channel() on tx_dma and rx_dma pointers that remain NULL whenever prepare_transfer() never ran. Dereferencing those pointers inside the DMA core triggers an oops in kernel context. The condition is deterministic and reachable through standard administrative unbind operations.
Root Cause
The root cause is a mismatched object lifecycle between allocation and deallocation paths [CWE-476]. DMA channel acquisition was moved into the transfer preparation function, but the symmetric release call in remove() was retained. This leaves the cleanup path operating on uninitialized channel pointers when the controller was probed but never used to perform a transfer.
Attack Vector
Exploitation requires local access with sufficient privilege to unbind the SPI controller driver or remove the kernel module. The issue was identified during code review of a controller deregistration fix and is not known to be exploited in the wild. The Exploit Prediction Scoring System (EPSS) lists the probability of exploitation as low. The realistic outcome is a local denial of service through kernel oops rather than code execution.
No public proof-of-concept code is available. The upstream fix removes the erroneous DMA channel release from the remove() path so that cleanup matches the deferred allocation introduced earlier.
Detection Methods for CVE-2026-46296
Indicators of Compromise
- Kernel oops messages referencing dma_release_channel invoked from s3c64xx_spi_remove in dmesg or journalctl -k
- Unexpected SPI controller unbind events followed by NULL pointer dereference backtraces
- System log entries showing module removal of spi_s3c64xx immediately preceding a kernel panic
Detection Strategies
- Inventory running kernel versions against the patched commits (1108b87, 1b66f16, 22788b1, 323a25, 45daacb) to identify exposed hosts
- Monitor /sys/bus/platform/drivers/s3c64xx-spi/unbind write events through audit subsystem rules
- Correlate kernel crash dumps with the spi-s3c64xx call stack to identify successful or attempted triggers
Monitoring Recommendations
- Forward kernel ring buffer messages to a centralized log platform and alert on BUG: unable to handle entries naming the SPI driver
- Track module load and unload activity for spi_s3c64xx via auditd MODULE_LOAD and MODULE_UNLOAD records
- Watch for repeated SPI driver bind and unbind cycles on the same device, which may indicate fuzzing or instability testing
How to Mitigate CVE-2026-46296
Immediate Actions Required
- Apply the upstream Linux kernel patches referenced in the stable tree commits listed in the advisory
- Restrict local user access to sysfs driver bind and unbind interfaces by enforcing root-only permissions on /sys/bus/platform/drivers/s3c64xx-spi/
- On embedded platforms using the s3c64xx SPI driver, prioritize firmware and kernel updates that include the corrective commits
Patch Information
The issue is resolved by removing the stale DMA channel release from the driver's remove() function. Fixes are available in stable kernels through the upstream commits 1108b8722b9f, 1b66f16a571a, 22788b1a8611, 323a258f4b19, and 45daacbead8a. Rebuild affected kernels from a stable branch that includes these commits, or install a vendor kernel update that backports the fix.
Workarounds
- Disable the spi-s3c64xx driver on systems that do not require it by blacklisting the module in /etc/modprobe.d/
- Avoid unbinding the SPI controller driver at runtime on unpatched kernels, particularly on production embedded systems
- Limit shell access on affected devices to trusted administrators until the patched kernel is deployed
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
