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.
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.
Metrics
Affected Vendors & Products
Advisories
No advisories yet.
Fixes
Solution
No solution given by the vendor.
Workaround
No workaround given by the vendor.
References
History
Thu, 17 Sep 2026 16:30:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Description | 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. | |
| Title | fuse: Fix the condition to enable over-io-uring | |
| First Time appeared |
Linux
Linux linux Kernel |
|
| CPEs | cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* | |
| Vendors & Products |
Linux
Linux linux Kernel |
|
| References |
|
Projects
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MITRE
Status: PUBLISHED
Assigner: Linux
Published:
Updated: 2026-09-17T16:06:08.197Z
Reserved: 2026-09-11T19:38:34.786Z
Link: CVE-2026-90095
Vulnrichment
No data.
NVD
Status : Received
Published: 2026-09-17T17:17:01.123
Modified: 2026-09-17T17:17:01.123
Link: CVE-2026-90095
Redhat
No data.
OpenCVE Enrichment
No data.
Weaknesses
No weakness.