CVE-2025-37765 in Linux
Summary
by MITRE • 05/01/2025
In the Linux kernel, the following vulnerability has been resolved:
drm/nouveau: prime: fix ttm_bo_delayed_delete oops
Fix an oops in ttm_bo_delayed_delete which results from dererencing a dangling pointer:
Oops: general protection fault, probably for non-canonical address 0x6b6b6b6b6b6b6b7b: 0000 [#1] PREEMPT SMP
CPU: 4 UID: 0 PID: 1082 Comm: kworker/u65:2 Not tainted 6.14.0-rc4-00267-g505460b44513-dirty #216 Hardware name: LENOVO 82N6/LNVNB161216, BIOS GKCN65WW 01/16/2024 Workqueue: ttm ttm_bo_delayed_delete [ttm]
RIP: 0010:dma_resv_iter_first_unlocked+0x55/0x290 Code: 31 f6 48 c7 c7 00 2b fa aa e8 97 bd 52 ff e8 a2 c1 53 00 5a 85 c0 74 48 e9 88 01 00 00 4c 89 63 20 4d 85 e4 0f 84 30 01 00 00 8b 44 24 10 c6 43 2c 01 48 89 df 89 43 28 e8 97 fd ff ff 4c 8b RSP: 0018:ffffbf9383473d60 EFLAGS: 00010202 RAX: 0000000000000001 RBX: ffffbf9383473d88 RCX: 0000000000000000 RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000 RBP: ffffbf9383473d78 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000000 R12: 6b6b6b6b6b6b6b6b R13: ffffa003bbf78580 R14: ffffa003a6728040 R15: 00000000000383cc FS: 0000000000000000(0000) GS:ffffa00991c00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000758348024dd0 CR3: 000000012c259000 CR4: 0000000000f50ef0 PKRU: 55555554 Call Trace: ? __die_body.cold+0x19/0x26 ? die_addr+0x3d/0x70 ? exc_general_protection+0x159/0x460 ? asm_exc_general_protection+0x27/0x30 ? dma_resv_iter_first_unlocked+0x55/0x290 dma_resv_wait_timeout+0x56/0x100 ttm_bo_delayed_delete+0x69/0xb0 [ttm]
process_one_work+0x217/0x5c0 worker_thread+0x1c8/0x3d0 ? apply_wqattrs_cleanup.part.0+0xc0/0xc0 kthread+0x10b/0x240 ? kthreads_online_cpu+0x140/0x140 ret_from_fork+0x40/0x70 ? kthreads_online_cpu+0x140/0x140 ret_from_fork_asm+0x11/0x20
The cause of this is:
- drm_prime_gem_destroy calls dma_buf_put(dma_buf) which releases the reference to the shared dma_buf. The reference count is 0, so the dma_buf is destroyed, which in turn decrements the corresponding amdgpu_bo reference count to 0, and the amdgpu_bo is destroyed - calling drm_gem_object_release then dma_resv_fini (which destroys the reservation object), then finally freeing the amdgpu_bo.
- nouveau_bo obj->bo.base.resv is now a dangling pointer to the memory formerly allocated to the amdgpu_bo.
- nouveau_gem_object_del calls ttm_bo_put(&nvbo->bo) which calls ttm_bo_release, which schedules ttm_bo_delayed_delete.
- ttm_bo_delayed_delete runs and dereferences the dangling resv pointer, resulting in a general protection fault.
Fix this by moving the drm_prime_gem_destroy call from nouveau_gem_object_del to nouveau_bo_del_ttm. This ensures that it will be run after ttm_bo_delayed_delete.
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Analysis
by VulDB Data Team • 05/27/2025
The vulnerability described in CVE-2025-37765 represents a critical null pointer dereference scenario within the Linux kernel's graphics subsystem, specifically affecting the nouveau driver's implementation of the TTM (Transportable TTM) memory management framework. This flaw manifests as a general protection fault when the kernel attempts to access memory through a dangling pointer reference, leading to system instability and potential denial of service conditions. The issue occurs during the cleanup process of graphics buffer objects, where improper ordering of resource deallocation operations creates a window where memory is freed but still referenced. The technical root cause involves the drm_prime_gem_destroy function being invoked too early in the destruction sequence, before the ttm_bo_delayed_delete workqueue function has completed its execution, resulting in a dereference of memory that has already been deallocated.
The exploitation of this vulnerability follows a specific sequence of operations that leverages the kernel's graphics buffer management subsystem. When a graphics buffer object is destroyed, the drm_prime_gem_destroy function is called which decrements the reference count of the shared dma_buf structure, ultimately leading to its destruction. This process triggers a cascade of cleanup operations including the release of the amdgpu_bo object, which in turn calls drm_gem_object_release followed by dma_resv_fini, resulting in the freeing of the reservation object memory. However, the nouveau_bo structure maintains a reference to this now-freed memory through its resv pointer, creating a dangling pointer condition. The subsequent invocation of ttm_bo_delayed_delete from the workqueue attempts to access this invalid memory reference, causing the kernel to generate a general protection fault and potentially crash the system.
This vulnerability directly relates to CWE-476, which describes the use of a null pointer dereference, and aligns with ATT&CK technique T1499.001 for Network Denial of Service. The operational impact of this flaw extends beyond simple system crashes, as it can be exploited to cause persistent system instability in graphics-intensive applications or services. The vulnerability affects systems utilizing the nouveau driver for NVIDIA graphics hardware, particularly those running kernel versions that include the affected TTM subsystem components. The exploitation requires specific conditions involving graphics buffer operations and memory management sequences, making it less common than simpler kernel vulnerabilities but still highly concerning for production environments.
The fix implemented addresses the core ordering issue by relocating the drm_prime_gem_destroy call from the nouveau_gem_object_del function to the nouveau_bo_del_ttm function. This reordering ensures that the TTM delayed deletion workqueue completes its execution before the resource cleanup operations that would invalidate the referenced memory. The solution follows established kernel development practices for managing object lifecycle dependencies and prevents the race condition that led to the dangling pointer dereference. This remediation aligns with security best practices for kernel memory management, ensuring proper resource cleanup sequencing and preventing the premature release of memory that could still be referenced by deferred operations. The fix maintains the intended functionality of both the DRM prime subsystem and the TTM memory management framework while eliminating the potential for system crashes and denial of service conditions.