CVE-2026-90095
UnknownSummary
In the Linux kernel, a fix was made to the condition that enables over-io-uring in FUSE. The fuse_uring_cmd() function now requires the FUSE_OVER_IO_URING flag to be set in the FUSE_INIT reply before accepting an IORING_OP_URING_CMD. Without this flag, there is a risk of deadlock when attempting to use io-uring. The change is trivial but alters behavior: FUSE servers must set this flag to handle io-uring.
Risk Assessment
Missing the appropriate flag can lead to system deadlocks, resulting in denial of service (DoS) or system hang. Administrators should ensure that their FUSE servers (e.g., libfuse) support the required attribute.
Recommendation
It is recommended to update the Linux kernel to a version containing this fix and verify that FUSE servers in the environment set the FUSE_OVER_IO_URING flag in the FUSE_INIT response.
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Original NVD description (English source)
In the Linux kernel, the following vulnerability has been resolved: fuse: Fix the condition to enable over-io-uring The existing condition in fuse_uring_cmd() is there only to avoid disabling io-uring for connections that already run with it, missing was a condition to refuse any IORING_OP_URING_CMD if the connection/channel didn't get enabled because of missing FUSE_INIT reply flag FUSE_OVER_IO_URING. Without the reply flag the barrier in fuse_uring_ready() doesn't work and IO could already be going on and cause deadlock states (at a minimum one between fch->bg_lock and queue->lock). The change itself is trivial, but brings behavior change, FUSE_OVER_IO_URING has to be set in the FUSE_INIT_REPLY by fuse servers to accept any IORING_OP_URING_CMD. Libfuse does that and the only non-libfuse implementation I found (fractal-fuse) also does it. Qemu patches for fuse-io-uring are not merged yet, as far as I know. Moved up is the smp_load_acquire(&fch->initialized) check, as a fuse-server implementation might try to setup io-uring before FUSE_INIT is processed and might have gotten -EOPNOTSUPP instead of -EAGAIN. Also fixed is a stale comment that explains the handling of the FUSE_OVER_IO_URING flag in early RFC versions. If there should be a report from any library or application we probably need to revert this commit.
Vulnerability data from NVD (NIST) · CISA KEV · EPSS