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CVE-2026-89742: rapidio: mport_cdev: fix use-after-free in dma_req_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: 2026-09-11 · updated 2026-10-19

Description

In the Linux kernel, the following vulnerability has been resolved: rapidio: mport_cdev: fix use-after-free in dma_req_free() dma_req_free() acquires buf_mutex through req->map, drops the mapping reference with kref_put(), and then dereferences req->map again to unlock the mutex. If kref_put() drops the last reference, mport_release_mapping() frees the mapping, and the subsequent mutex_unlock() dereferences a freed object. This is a use-after-free. Fix this by caching map and md before kref_put(), clearing req->map while holding buf_mutex, and using the cached md for mutex unlocking. The bug is reachable from userspace via the RapidIO mport character device interface.

Affected products

• Linux kernel: 4.6 — fixed in 7.3

How to fix

Upgrade to a fixed version: Linux kernel 7.3. Check the vendor advisory for mitigations.

References

• https://git.kernel.org/stable/c/00c5ed913b0dc563fbeb8a97ea8916c03bbbbf6a
• https://git.kernel.org/stable/c/211c68d817a3d9dc14c0026a59da7cac30f8147e
• https://git.kernel.org/stable/c/26ccfe7d69e27b0d933ae0a64a23a0cb9b9a85a6
• https://git.kernel.org/stable/c/5cbef379a94b161726c5f504598bf4791d45cedc
• https://git.kernel.org/stable/c/9a9929ec875ff20922c90c96fd544ae8a2a61a8d
• https://git.kernel.org/stable/c/bd8881c24a9520f9c3d3e855d866197f63e471a7
• https://git.kernel.org/stable/c/e6e925cc1f8067c65c7bec3da50a0ead3b3ef4e0
• https://git.kernel.org/stable/c/fc79c07cdcde02c5b17633d78777de6ac2c14b29

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