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CVE-2025-39871: dmaengine: idxd: Remove improper idxd_free

• Severity: high (CVSS 7.8 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.2% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2025-09-23 · updated 2026-10-19
• Weakness: CWE-416

Description

In the Linux kernel, the following vulnerability has been resolved: dmaengine: idxd: Remove improper idxd_free The call to idxd_free() introduces a duplicate put_device() leading to a reference count underflow: refcount_t: underflow; use-after-free. WARNING: CPU: 15 PID: 4428 at lib/refcount.c:28 refcount_warn_saturate+0xbe/0x110 ... Call Trace: <TASK> idxd_remove+0xe4/0x120 [idxd] pci_device_remove+0x3f/0xb0 device_release_driver_internal+0x197/0x200 driver_detach+0x48/0x90 bus_remove_driver+0x74/0xf0 pci_unregister_driver+0x2e/0xb0 idxd_exit_module+0x34/0x7a0 [idxd] __do_sys_delete_module.constprop.0+0x183/0x280 do_syscall_64+0x54/0xd70 entry_SYSCALL_64_after_hwframe+0x76/0x7e The idxd_unregister_devices() which is invoked at the very beginning of idxd_remove(), already takes care of the necessary put_device() through the following call path: idxd_unregister_devices() -> device_unregister() -> put_device() In addition, when CONFIG_DEBUG_KOBJECT_RELEASE is enabled, put_device() may trigger asynchronous cleanup via schedule_delayed_work(). If idxd_free() is called immediately after, it can result in a use-after-free. Remove the improper idxd_free() to avoid both the refcount underflow and potential memory corruption during module unload.

Affected products

• Linux kernel: from 6.1.140 before 6.2; from 6.6.92 before 6.6.107; from 6.12.30 before 6.12.48; from 6.14.8 before 6.15; from 6.15.1 before 6.16.8; 6.15, 6.15-rc7, 6.17-rc1, 6.17-rc2, 6.17-rc3, 6.17-rc4 (+1) — fixed in 6.12.48, 6.15, 6.16.8, 6.2, 6.6.107

How to fix

Upgrade to a fixed version: Linux kernel 6.12.48, 6.15, 6.16.8, 6.2. Check the vendor advisory for mitigations.

References

• https://git.kernel.org/stable/c/0e95ee7f532b21206fe3f1c4054002b0d21e3b9c
• https://git.kernel.org/stable/c/24414bbcb37e1af95190af36c21ae51d497e1a9e
• https://git.kernel.org/stable/c/da4fbc1488a4cec6748da685181ee4449a878dac
• https://git.kernel.org/stable/c/dd7a7e43269711d757fc260b0bbdf7138f75de11
• https://git.kernel.org/stable/c/f41c538881eec4dcf5961a242097d447f848cda6
• https://cert-portal.siemens.com/productcert/html/ssa-019113.html
• https://cert-portal.siemens.com/productcert/html/ssa-457936.html

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