CVE-2026-98094

Summary

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

staging: fbtft: make dirty_lock IRQ-safe

fbtft_mkdirty() can be reached from the fbcon rendering path while processing printk() in hardirq context. Meanwhile, dirty_lock is also taken by fbtft_deferred_io() in workqueue context with local interrupts enabled.

Lockdep reports a possible IRQ lock inversion involving dirty_lock and console_owner. A hardirq can interrupt a CPU holding dirty_lock and enter the console rendering path, which can attempt to acquire dirty_lock again.

The following lockdep report was observed on an RK3566 system with CONFIG_PROVE_LOCKING enabled:

WARNING: possible irq lock inversion dependency detected swapper/2/0 just changed the state of lock: (console_owner){-…}-{0:0} but this lock took another, HARDIRQ-unsafe lock in the past: (&par->dirty_lock){+.+.}-{2:2}

CPU0 CPU1

lock(&par->dirty_lock); local_irq_disable(); lock(console_owner); lock(&par->dirty_lock); <Interrupt> lock(console_owner);

*** DEADLOCK ***

Use spin_lock_irqsave() for fbtft_mkdirty() and spin_lock_irq() for fbtft_deferred_io(). They only access the dirty line range, so the IRQ-off regions remain short.

Affected Software

Weaknesses

References

• https://git.kernel.org/stable/c/2a609e29efbba79f9abd68c4ec8a2bd7ecf291e7
• https://git.kernel.org/stable/c/f0c869df2c33793c8828acaab3e4a5e0176f9f00
• https://git.kernel.org/stable/c/dcb48fde8003492256dee45815144aa5ed26ce7c
• https://git.kernel.org/stable/c/f576944a59f31bcffff121117ebf452c5dd162b7

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