CVE-2026-93050

Summary

In the Linux kernel, the following vulnerability has been resolved:

ipack: ipoctal: fix UAF, null-ptr-deref, and use-after-free in cleanup on remove

Three issues arise when the device is removed while a tty session is still active:

1. UAF of struct ipoctal: the remove callback frees ipoctal via kfree() while tty ops may still access it. Fix by introducing kref-based lifetime management — kref is taken in install() when a tty is opened and released in cleanup() when the tty is finally destroyed; remove() uses kref_put() instead of kfree().

2. NULL dereference in ipoctal_write_tty(): __ipoctal_remove() frees xmit_buf via tty_port_free_xmit_buf() while a userspace process may still hold the tty fd and call write(). Fix by checking for NULL xmit_buf in ipoctal_write_tty().

3. UAF in ipoctal_cleanup(): ipack_put_carrier(ipoctal->dev) dereferences ipoctal->dev after the ipack_device has been freed by ipack_device_del(). Fix by caching ipoctal->carrier_owner during probe() and calling module_put() on the cached pointer directly in cleanup(), avoiding any access to ipoctal->dev.

Also introduce a "removed" flag in struct ipoctal, set at the start of __ipoctal_remove(), and checked in every tty op that accesses hardware resources (port_activate, write_tty, set_termios, hangup, shutdown). This prevents page faults when devm_ioremap() regions are unmapped after remove() returns.

Affected Software

Weaknesses

References

• https://git.kernel.org/stable/c/ab5f5b27a340004b92252c6a5f23bf1c6cf3b02a
• https://git.kernel.org/stable/c/c92ef8fd834521f0b788e0511976c689fe57c63c
• https://git.kernel.org/stable/c/a4613140f01bd0fb9980e2746ed9aaa65a29b5d6
• https://git.kernel.org/stable/c/1a3258e105f711538201bdd2ac2a05b11554eabc
• https://git.kernel.org/stable/c/4a6518be316029650301f2a5e8f0def229b895d9
• https://git.kernel.org/stable/c/b6b5d64cb161a28347d64dc3168a636c4abb68d5

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