CVE-2026-80859fuse: fix missing barrier when checking io-uring readiness

Official description

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.

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/8974575898cd7a4c818088f102b2e7a0286d3302
• https://git.kernel.org/stable/c/dd9c835709f4bb3e4256eea7573e4e6e18f956de
• https://git.kernel.org/stable/c/edb310bc27f0ad83e7fd558a3caf1a94ca511654