From 75467f60a3d14f08f86f2b353298d2826382ff23 Mon Sep 17 00:00:00 2001 From: Linus Torvalds Date: Fri, 25 Sep 2026 15:55:03 -0700 Subject: Merge tag 'ipe-pr-20260925' of git://git.kernel.org/pub/scm/linux/kernel/git/wufan/ipe Pull IPE fixes from Fan Wu: "Two fixes for use-after-free issues found by recent LLM-assisted code analysis. - move successful policy load auditing under the new policy directory's inode lock, preventing a concurrent policy deletion from freeing the policy while it is still being audited - protect the dm-verity root hash with RCU, preventing policy evaluation from racing with root hash replacement during preresume" * tag 'ipe-pr-20260925' of git://git.kernel.org/pub/scm/linux/kernel/git/wufan/ipe: ipe: protect the dm-verity root hash with RCU ipe: fix use-after-free when auditing a newly loaded policy --- .../filesystems/fuse/uapi/fuse-uapi-io-uring.rst | 126 +++++++++++++++++++++ 1 file changed, 126 insertions(+) create mode 100644 Documentation/filesystems/fuse/uapi/fuse-uapi-io-uring.rst (limited to 'Documentation/filesystems/fuse/uapi') diff --git a/Documentation/filesystems/fuse/uapi/fuse-uapi-io-uring.rst b/Documentation/filesystems/fuse/uapi/fuse-uapi-io-uring.rst new file mode 100644 index 000000000..8367be7ea --- /dev/null +++ b/Documentation/filesystems/fuse/uapi/fuse-uapi-io-uring.rst @@ -0,0 +1,126 @@ +.. SPDX-License-Identifier: GPL-2.0 + +===================================== +FUSE-over-io-uring uapi documentation +===================================== + +Commands +======== + +``enum fuse_uring_cmd``: + +``FUSE_IO_URING_CMD_ADD_QUEUE`` + Create a queue identified by ``fuse_uring_cmd_req.qid``. Queue-wide + options are passed in ``fuse_uring_cmd_req.flags``: + + ``FUSE_URING_ZERO_COPY`` + Enable zero-copy on this queue. Requires ``CAP_SYS_ADMIN`` and a buffer + pool, which is added separately via ``ADD_BUFPOOL`` before registering + entries (see `Zero-copy`_). + +``FUSE_IO_URING_CMD_ADD_BUFPOOL`` + Register the payload buffer pool for an existing queue. The server provides + a single contiguous region in ``fuse_uring_cmd_req.bufpool.uaddr`` / + ``.len``. This command must be issued after ``ADD_QUEUE`` and before + registering any payload-carrying entries on that queue. + ``fuse_uring_cmd_req.flags`` must be 0. Submitting this command with + ``IORING_URING_CMD_FIXED`` marks the pool as registered, which avoids per + i/o pinning/unpinning and mapping overhead (see `Buffer pools`_). + +``FUSE_IO_URING_CMD_REGISTER`` + Register a ring entry (a long-lived SQE that carries the request header + iovec). For a zero-copy queue, ``fuse_uring_cmd_req.ent_zero_copy_buf_index`` + indicates the reserved registered buffer table slot this entry uses for + zero-copy (see `Zero-copy`_). + +``FUSE_IO_URING_CMD_COMMIT_AND_FETCH`` + Commit the reply for a completed request and fetch the next one. The + request is identified by ``fuse_uring_cmd_req.commit_id`` (the value the + kernel reported in ``fuse_uring_ent_in_out.commit_id``). + +Structures +========== + +``struct fuse_uring_cmd_req`` (80-byte SQE command area): + +============================ ================================================== +Field Meaning +============================ ================================================== +``flags`` Command-specific flags (see each command). +``commit_id`` Request id, for ``COMMIT_AND_FETCH``. +``qid`` Queue index. +``bufpool.uaddr`` Pool base address, for ``ADD_BUFPOOL``. +``bufpool.len`` Pool length in bytes, for ``ADD_BUFPOOL``. +``bufpool.reserved`` Must be 0, for ``ADD_BUFPOOL``. +``ent_zero_copy_buf_index`` Per-entry zero-copy slot, for ``REGISTER``. +============================ ================================================== + +``struct fuse_uring_ent_in_out`` (reported by the kernel per request): + +============================ ================================================== +Field Meaning +============================ ================================================== +``flags`` ``FUSE_URING_ENT_ZERO_COPY`` if zero-copied. +``commit_id`` Id to echo back in ``COMMIT_AND_FETCH``. +``payload_sz`` Total payload size in bytes (see `Zero-copy`_). +``offset`` Payload buffer offset within the pool. +============================ ================================================== + +Buffer pools +============ +Setup: + +* Issue ``ADD_QUEUE`` for the qid. +* Issue ``ADD_BUFPOOL`` with ``bufpool.uaddr`` and ``bufpool.len`` pointing + at the region. +* Register entries with ``REGISTER``. + +For every request that has a payload, the kernel reports where the payload +lives in ``struct fuse_uring_ent_in_out`` (part of +``struct fuse_uring_req_header``): + +``offset`` + Byte offset, within the pool region, for this request's payload buffer. + The server adds this to the pool base address to locate the payload. + +``payload_sz`` + Number of payload bytes for this request. + +To use registered buffers, the server registers the pool region with io_uring +and submits ``ADD_BUFPOOL`` with ``IORING_URING_CMD_FIXED`` set in +``sqe->uring_cmd_flags`` and the index of the registered bufpool in +``sqe->buf_index``. Every SQE the server submits afterwards must follow the +same fixed-buffer protocol, carrying ``IORING_URING_CMD_FIXED`` and that same +``sqe->buf_index``. The same registered buffer can be reused for the server's +backing-store I/O as well (e.g. ``IORING_OP_READ_FIXED`` / +``IORING_OP_WRITE_FIXED``). + +Zero-copy +========= +Requirements: + +* The server must be privileged (``CAP_SYS_ADMIN``). +* A zero-copy queue: ``ADD_QUEUE`` with the ``FUSE_URING_ZERO_COPY`` flag set. +* A buffer pool: ``ADD_BUFPOOL``. +* For each entry, ``REGISTER`` with ``ent_zero_copy_buf_index`` set to the + index this entry uses in the server's io_uring registered-buffer table. + This is where the kernel registers the request's pages for the server to + access (it is separate from the payload pool). On a non-zero-copy queue this + field must be 0. + +Zero-copy is selected per open file. The server sets the open-file flag in +the ``FUSE_OPEN`` / ``FUSE_CREATE`` reply: + +``FOPEN_IO_URING_ZERO_COPY`` + Reads/writes on this open file should use zero-copy. + +For a request that is zero-copied, the kernel sets ``FUSE_URING_ENT_ZERO_COPY`` +in ``fuse_uring_ent_in_out.flags`` and places the request's pages at the +entry's ``ent_zero_copy_buf_index``. The server then issues +``IORING_OP_READ_FIXED`` / ``IORING_OP_WRITE_FIXED`` against that index to +transfer the data directly to/from the client's pages. + +For such a request, ``payload_sz`` includes the zero-copied page bytes +(transferred via the registered buffer at ``ent_zero_copy_buf_index``). Any +non-page-backed args (e.g. op headers) are still copied through the pool +payload buffer at ``offset``. -- cgit v1.3.1