CVE-2026-72482: gpib: fix double decrement of descriptor_busy in command_ioctl()

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: 2026-08-15 · updated 2026-08-17

Description

In the Linux kernel, the following vulnerability has been resolved: gpib: fix double decrement of descriptor_busy in command_ioctl() commit d1857f8296dc ("gpib: fix use-after-free in IO ioctl handlers") introduced a descriptor_busy reference counter to pin struct gpib_descriptor across IO ioctl operations. In command_ioctl(), the error path inside the loop decrements descriptor_busy and breaks, but execution then falls through to the unconditional decrement after the loop, underflowing the counter to -1. This re-enables the use-after-free that the original fix was meant to prevent: a concurrent close_dev_ioctl() sees descriptor_busy == 0 on an actively-used descriptor and frees it. Remove the early decrement from the error path. The post-loop decrement already handles all exit paths, matching the correct pattern used in read_ioctl() and write_ioctl().

Affected products

Linux kernel: from 6.18.22 before 6.18.40; from 6.19.12 before 6.20; 7.0 — fixed in 6.18.40, 6.20, 7.2

How to fix

Upgrade to a fixed version: Linux kernel 6.18.40, 6.20, 7.2. Check the vendor advisory for mitigations.

References

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