CVE-2026-68239: drm/ttm: Account for NULL and handle pages in ttm_pool_backup
In the Linux kernel, the following vulnerability has been resolved:
drm/ttm: Account for NULL and handle pages in ttmpoolbackup
Pages in ttmpoolbackup can be NULL or backup handles (ttmbackuppageptrishandle()), neither of which can be passed to setpagesarraywb() or freed. Add a dedicated WB pass before the dma/purge loop that walks allocations using the same i += numpages stride, skipping NULL and handle entries, and calls setpagesarraywb() 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:cpaprocessfault+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> changepageattrsetclr+0x989/0xe90 ? purgevmaparealazy+0x6c/0x3a0 ? vmunmapaliases+0x250/0x2a0 setpagesarraywb+0x7f/0x120 ttmpoolbackup+0x4c9/0x5b0 [ttm] ? dmaresvwaittimeout+0x3b/0xf0 ttmttbackup+0x32/0x60 [ttm] ttmboshrink+0x66/0x110 [ttm] xeboshrinkpurge+0x12b/0x1b0 [xe] xeboshrink+0xbb/0x270 [xe] xeshrinkerwalk+0xf7/0x160 [xe] xeshrinkerwalk+0x9d/0xc0 [xe] xeshrinkerscan+0x11f/0x210 [xe] doshrinkslab+0x13b/0x270 shrinkslab+0xf1/0x400 shrinknode+0x352/0x8a0 balancepgdat+0x32c/0x700 kswapd+0x205/0x2f0 ? pfxautoremovewakefunction+0x10/0x10 ? pfxkswapd+0x10/0x10 kthread+0xd1/0x110 ? pfxkthread+0x10/0x10 retfromfork+0x1b1/0x200 ? pfxkthread+0x10/0x10 retfromforkasm+0x1a/0x30 </TASK>
Affected Software
Event History
Frequently Asked Questions
What is the severity of CVE-2026-68239?
CVE-2026-68239 has a risk rating of 37, indicating a moderate severity.
What is the main issue described in CVE-2026-68239?
CVE-2026-68239 addresses a null pointer dereference in the Linux kernel's ttm_pool_backup.
How do I fix CVE-2026-68239?
To mitigate CVE-2026-68239, users should update their Linux kernel to the latest patched version that resolves this vulnerability.
Which component is affected by CVE-2026-68239?
CVE-2026-68239 affects the Direct Rendering Manager (DRM) implementation in the Linux kernel.
What can happen if CVE-2026-68239 is exploited?
Exploitation of CVE-2026-68239 could lead to system crashes or instability due to the null pointer dereference.