CVE-2026-98270 in Linux
Summary
by MITRE • 10/06/2026
In the Linux kernel, the following vulnerability has been resolved:
drm/amdgpu: check ras and obj before dereference
nbio_v7_9_handle_ras_controller_intr_no_bifring() dereferences ras and obj without checking either for NULL. Both amdgpu_ras_get_context() and amdgpu_ras_find_obj() can return NULL, e.g. during the window between adev->nbio.ras being set (early in amdgpu_ras_init(), by design, to enable the fatal-error interrupt as soon as possible) and the PCIE_BIF ras object actually being created in RAS late_init. Any interrupt in that window crashes in hard-IRQ context.
This is analogous to commit d190b459b2a4 ("drm/amdgpu: the warning dereferencing obj for nbio_v7_4"), which fixed the same issue in the nbio_v7_4 handler.
Found by Linux Verification Center (linuxtesting.org) with SVACE.
(cherry picked from commit c7071767a50a32ed727cf800ac84372429e3b4b3)
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Analysis
by VulDB Data Team • 10/06/2026
The Linux kernel driver for AMD graphics processing units, specifically the amdgpu subsystem, contains a critical null pointer dereference vulnerability within the hardware interrupt handling routine. The function nbio_v7_9_handle_ras_controller_intr_no_bifring is responsible for managing RAS (Reliability, Availability, and Service) controller interrupts on certain NBIO v7.9 hardware revisions. During execution, this handler attempts to access two critical data structures by dereferencing pointers named ras and obj without performing any prior validation checks for null values. This oversight creates a direct path to kernel panic or system crash when these pointers are unexpectedly empty during specific operational windows.
The root cause of this vulnerability lies in the initialization sequence of the RAS subsystem within the amdgpu driver. The function amdgpu_ras_init sets up the fatal-error interrupt mechanism early in its execution flow by assigning a value to adev->nbio.ras, effectively enabling the hardware to generate interrupts immediately upon detection of errors. However, the actual PCIE_BIF RAS object, which is required for proper handling of these specific interrupts, is not created until the late initialization phase of the RAS subsystem completes. This creates a race condition window where the interrupt handler may be invoked by the hardware before the necessary data structures have been fully allocated and initialized.
Within this temporal gap between early enablement and late object creation, calls to amdgpu_ras_get_context() and amdgpu_ras_find_obj() can legitimately return NULL pointers because the underlying resources are not yet available. When nbio_v7_9_handle_rif_controller_intr_no_bifring proceeds to dereference these null pointers in hard-IRQ context, it triggers a kernel oops or panic due to invalid memory access. Hard interrupt contexts do not allow for sleeping or complex error recovery mechanisms that might otherwise mitigate such issues, making the resulting crash immediate and often unrecoverable without a system reboot.
This vulnerability is analogous to previous fixes applied to older hardware revisions, specifically commit d190b459b2a4 which addressed an identical dereferencing issue in the nbio_v7_4 handler. The discovery of this flaw was facilitated by static analysis tools from the Linux Verification Center using SVACE, highlighting the importance of rigorous automated verification in kernel development to catch logic errors that arise during complex initialization sequences.
From a classification perspective, this vulnerability aligns with CWE-476, which denotes NULL Pointer Dereference. In terms of attack vectors and operational impact, while typically triggered by internal race conditions rather than direct external exploitation, it falls under the broader category of availability impacts associated with Denial of Service via system crash. It relates to ATT&CK techniques involving resource exhaustion or disruption through kernel instability, although in this specific case, the trigger is often hardware-generated interrupts during a vulnerable initialization window rather than malicious input manipulation.
To mitigate this vulnerability, it is essential that developers ensure all pointer dereferences are guarded by explicit null checks before access. In the context of interrupt handlers, especially those running in hard-IRQ context where sleeping functions cannot be used, defensive programming practices must include verifying the validity of returned pointers from helper functions like amdgpu_ras_get_context and amdgpu_ras_find_obj. If a pointer is found to be null during this specific initialization window, the handler should either return immediately without processing or defer handling until the resources are guaranteed to be available, depending on the interrupt semantics. Applying the patch that introduces these checks ensures system stability by preventing crashes caused by premature access to uninitialized driver structures.