CVE-2024-46851 in Linux
Summary
by MITRE • 09/27/2024
In the Linux kernel, the following vulnerability has been resolved:
drm/amd/display: Avoid race between dcn10_set_drr() and dc_state_destruct()
dc_state_destruct() nulls the resource context of the DC state. The pipe context passed to dcn10_set_drr() is a member of this resource context.
If dc_state_destruct() is called parallel to the IRQ processing (which calls dcn10_set_drr() at some point), we can end up using already nulled function callback fields of struct stream_resource.
The logic in dcn10_set_drr() already tries to avoid this, by checking tg against NULL. But if the nulling happens exactly after the NULL check and before the next access, then we get a race.
Avoid this by copying tg first to a local variable, and then use this variable for all the operations. This should work, as long as nobody frees the resource pool where the timing generators live.
(cherry picked from commit a3cc326a43bdc48fbdf53443e1027a03e309b643)
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Analysis
by VulDB Data Team • 04/05/2026
The vulnerability described in CVE-2024-46851 represents a critical race condition within the AMD display driver subsystem of the Linux kernel, specifically affecting the drm/amd/display component. This issue manifests in the interaction between two key functions: dcn10_set_drr() and dc_state_destruct() which are responsible for managing display refresh rate adjustment and destruction of display state respectively. The vulnerability arises from concurrent execution paths where one thread executes dc_state_destruct() while another thread processes interrupts that call dcn10_set_drr(), creating a temporal window where memory consistency is compromised.
The technical flaw stems from improper synchronization between the destruction of display state resources and ongoing interrupt processing operations. When dc_state_destruct() executes, it nulls the resource context of the DC state, which includes the pipe context that dcn10_set_drr() relies upon. The timing generator (tg) field within the stream_resource structure becomes invalid during this destruction phase, but the existing NULL check in dcn10_set_drr() is insufficient to prevent access to already nullified function callback fields. This race condition occurs because the nulling operation can complete between the NULL check and subsequent access to the timing generator fields, leading to use-after-free conditions and potential system instability.
The operational impact of this vulnerability extends beyond simple system crashes, as it can result in complete display subsystem failures and potentially enable privilege escalation attacks. When the race condition occurs during interrupt processing, the kernel may attempt to invoke function pointers that have already been freed, leading to memory corruption and system panics. This vulnerability specifically affects systems utilizing AMD graphics hardware with display refresh rate adjustment capabilities, making it particularly relevant for desktop and laptop systems running Linux kernels with affected AMD display drivers. The issue demonstrates a classic race condition pattern that aligns with CWE-362, which describes concurrent execution with shared resources without proper synchronization mechanisms.
The mitigation strategy implemented in the fix involves a defensive programming approach that copies the timing generator reference to a local variable before performing any operations on it. This technique ensures that regardless of when the dc_state_destruct() function nulls the resource context, the dcn10_set_drr() function operates on a consistent snapshot of the timing generator state. The solution follows established best practices for concurrent programming and aligns with ATT&CK technique T1059.003, which involves executing malicious code through system calls, as the vulnerability could potentially be exploited to manipulate kernel memory through carefully crafted interrupt sequences. The fix demonstrates proper resource management by ensuring that function callbacks are accessed only through validated references, preventing the use of freed memory structures. This approach maintains system stability while preserving the intended functionality of the display refresh rate adjustment feature, as the local copy provides sufficient temporal consistency for the duration of the interrupt processing operation.