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        "cveId": "CVE-2021-47142",
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        "assignerShortName": "Linux",
        "dateReserved": "2024-03-04T18:12:48.842Z",
        "datePublished": "2024-03-25T09:07:40.374Z",
        "dateUpdated": "2026-08-05T08:46:18.601Z"
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                    "value": "In the Linux kernel, the following vulnerability has been resolved:\n\ndrm/amdgpu: Fix a use-after-free\n\nlooks like we forget to set ttm->sg to NULL.\nHit panic below\n\n[ 1235.844104] general protection fault, probably for non-canonical address 0x6b6b6b6b6b6b7b4b: 0000 [#1] SMP DEBUG_PAGEALLOC NOPTI\n[ 1235.989074] Call Trace:\n[ 1235.991751]  sg_free_table+0x17/0x20\n[ 1235.995667]  amdgpu_ttm_backend_unbind.cold+0x4d/0xf7 [amdgpu]\n[ 1236.002288]  amdgpu_ttm_backend_destroy+0x29/0x130 [amdgpu]\n[ 1236.008464]  ttm_tt_destroy+0x1e/0x30 [ttm]\n[ 1236.013066]  ttm_bo_cleanup_memtype_use+0x51/0xa0 [ttm]\n[ 1236.018783]  ttm_bo_release+0x262/0xa50 [ttm]\n[ 1236.023547]  ttm_bo_put+0x82/0xd0 [ttm]\n[ 1236.027766]  amdgpu_bo_unref+0x26/0x50 [amdgpu]\n[ 1236.032809]  amdgpu_amdkfd_gpuvm_alloc_memory_of_gpu+0x7aa/0xd90 [amdgpu]\n[ 1236.040400]  kfd_ioctl_alloc_memory_of_gpu+0xe2/0x330 [amdgpu]\n[ 1236.046912]  kfd_ioctl+0x463/0x690 [amdgpu]"
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                            "value": "AV:L - The bug is reached through local ioctls on /dev/kfd (kfd_ioctl_alloc_memory_of_gpu with KFD_IOC_ALLOC_MEM_FLAGS_USERPTR) or the DRM render-node AMDGPU_GEM_USERPTR path, not via network packet processing.\nAC:L - An unprivileged local attacker can reliably drive the userptr populate/unpopulate/destroy sequence via KFD/DRM ioctls and control concurrent GPU memory operations; no conditions outside attacker influence are required to hit the dangling ttm->sg use.\nPR:L - /dev/kfd and DRM render nodes are mode 0660 group render (with uaccess for seated users); kfd_open and the GEM userptr ioctl perform no capability checks, so a normal unprivileged render-group user can reach the vulnerable code.\nUI:N - Exploitation requires only the attacker’s own ioctl calls against the GPU device nodes; no separate victim action is needed.\nS:U - The vulnerability corrupts kernel memory within the host kernel’s authority and enables local privilege escalation, but does not cross a VM/IOMMU/sandbox boundary.\nC:H - This is a use-after-free of the kmalloc’d sg_table: after kfree(ttm->sg) without NULLing, later unbind reads the freed object, and reclaim/spray of that slab can expose arbitrary kernel memory contents.\nI:H - Use of the reclaimed dangling ttm->sg in sg_free_table() yields an attacker-controlled scatterlist walk/arbitrary free primitive, which is a standard path to arbitrary kernel write and control-flow hijacking.\nA:H - The demonstrated failure is a kernel general protection fault/oops in sg_free_table during amdgpu_ttm_backend_unbind, so availability impact is complete host crash."
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