CVE-2026-80859

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

fuse: fix missing barrier when checking io-uring readiness

fuse block alloc() reads fch->initialized and then fch->io uring. fch->io uring is set before fch->initialized, ordered by the smp wmb() in fuse chan set intialized(), but fuse block alloc() has no matching read barrier between the two loads.

This may lead a CPU to observe fch->initialized=1 but fch->io uring=0, and skip the check that blocks request allocation until the io-uring queues are ready. This can reintroduce the lock-order inversion deadlock that commit 3393ff964e0f prevents.

Add an smp rmb() barrier to pair with the smp wmb() in fuse chan set initialized() to prevent this.