CVE-2026-68239
Received Received - Intake

Kernel NULL Pointer Dereference in Linux Kernel TTM Memory Management

Publication date: 2026-08-10

Last updated on: 2026-08-10

Assigner: kernel.org

Description
In the Linux kernel, the following vulnerability has been resolved: drm/ttm: Account for NULL and handle pages in ttm_pool_backup Pages in ttm_pool_backup can be NULL or backup handles (ttm_backup_page_ptr_is_handle()), neither of which can be passed to set_pages_array_wb() or freed. Add a dedicated WB pass before the dma/purge loop that walks allocations using the same i += num_pages stride, skipping NULL and handle entries, and calls set_pages_array_wb() once per contiguous run of real pages. Apply the same NULL/handle guard to the dma/purge loop. Fixes the following oops: Oops: general protection fault, kernel NULL pointer dereference 0x0: 0000 [#1] SMP NOPTI RIP: 0010:__cpa_process_fault+0xf8/0x770 RSP: 0018:ffffc90000a87718 EFLAGS: 00010287 RAX: 0000000000000000 RBX: ffffc90000a87868 RCX: 0000000000000000 RDX: 0000000000001000 RSI: 0005088000000000 RDI: ffffffff827c5f34 RBP: 0005088000000000 R08: ffffc90000a877cb R09: ffffc90000a877d0 R10: 0000000000000000 R11: 000000000000001b R12: 000ffffffffff000 R13: ffffc90000a87868 R14: ffffc90000a87868 R15: ffff88815b882ae0 FS: 0000000000000000(0000) GS:ffff8884ec840000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f930b844000 CR3: 000000000262e003 CR4: 0000000008f70ef0 PKRU: 55555554 Call Trace: <TASK> __change_page_attr_set_clr+0x989/0xe90 ? __purge_vmap_area_lazy+0x6c/0x3a0 ? _vm_unmap_aliases+0x250/0x2a0 set_pages_array_wb+0x7f/0x120 ttm_pool_backup+0x4c9/0x5b0 [ttm] ? dma_resv_wait_timeout+0x3b/0xf0 ttm_tt_backup+0x32/0x60 [ttm] ttm_bo_shrink+0x66/0x110 [ttm] xe_bo_shrink_purge+0x12b/0x1b0 [xe] xe_bo_shrink+0xbb/0x270 [xe] __xe_shrinker_walk+0xf7/0x160 [xe] xe_shrinker_walk+0x9d/0xc0 [xe] xe_shrinker_scan+0x11f/0x210 [xe] do_shrink_slab+0x13b/0x270 shrink_slab+0xf1/0x400 shrink_node+0x352/0x8a0 balance_pgdat+0x32c/0x700 kswapd+0x205/0x2f0 ? __pfx_autoremove_wake_function+0x10/0x10 ? __pfx_kswapd+0x10/0x10 kthread+0xd1/0x110 ? __pfx_kthread+0x10/0x10 ret_from_fork+0x1b1/0x200 ? __pfx_kthread+0x10/0x10 ret_from_fork_asm+0x1a/0x30 </TASK>

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Meta Information

Published
2026-08-10
Last Modified
2026-08-10
Generated
2026-08-10
AI Q&A
2026-08-10
EPSS Evaluated
N/A
NVD
CVE-2026-68239
EUVD
EUVD-2026-55340

Affected Vendors & Products

Currently, no data is known.

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Exploitability

CWE
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KEV
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CWE ID Description
CWE-UNKNOWN

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Executive Summary

This vulnerability in the Linux kernel involves a NULL pointer dereference in the TTM (Translation Table Maps) memory management subsystem. The issue occurs in the ttm_pool_backup function where NULL pages or backup handles are incorrectly passed to set_pages_array_wb() or freed, causing a kernel oops (crash). The fix adds checks to skip NULL and handle entries during memory operations.

Detection Guidance

This vulnerability is specific to the Linux kernel's TTM (Translation Table Maps) memory management subsystem. Detection requires checking kernel logs for NULL pointer dereference oops related to ttm_pool_backup or set_pages_array_wb. Monitor system logs for kernel crashes or errors involving these functions.

Impact Analysis

This vulnerability can cause system crashes (kernel oops) due to NULL pointer dereferences, leading to unexpected reboots or service interruptions. Systems using affected Linux kernel versions with TTM-based graphics drivers may experience instability or data corruption during memory operations.

Mitigation Strategies

Apply the latest kernel security updates that include the fix for this vulnerability. If immediate patching is not possible, consider disabling affected GPU drivers or services using TTM until the update is applied. Monitor kernel logs for signs of exploitation or crashes.

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