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io_install_bpf() only rejects a second registration on the ctx side
(ctx->bpf_ops) and sets the per-map back-pointer ops->priv
unconditionally. The struct_ops link path never advances a map past
BPF_STRUCT_OPS_STATE_READY, so the same io_uring_bpf_ops map can be
registered more than once, and bpf_io_reg() re-resolves the target ring
via fget(ops->ring_fd) on every call. A caller can therefore point the
same ring_fd at a different io_ring_ctx between two BPF_LINK_CREATE
calls.
The second registration passes the ctx->bpf_ops check (the new ctx has
none) and overwrites ops->priv, orphaning the first ctx. Teardown
(io_eject_bpf()/bpf_io_unreg()) only reaches a ctx through ops->priv, so
the orphaned ctx is never torn down: its ctx->loop_step keeps pointing
into the struct_ops trampoline, which is freed once the map is gone. A
later io_uring_enter() on the orphaned ring then calls the dangling
ctx->loop_step from io_run_loop() -- a use-after-free of freed
executable memory, reachable by a task with CAP_BPF + CAP_PERFMON.
Reject registration when ops->priv is already set, as hid_bpf_reg()
does for its struct_ops.
Cc: stable@vger.kernel.org
Fixes: 98f37634b12b ("io_uring/bpf-ops: implement bpf ops registration")
Signed-off-by: Woraphat Khiaodaeng <worapat.kd2@gmail.com>
Reviewed-by: Gabriel Krisman Bertazi <krisman@suse.de>
Reviewed-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://patch.msgid.link/20260717154537.129736-1-worapat.kd2@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
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BPF programs should have no need in looking into struct io_ring_ctx, if
anything, most of such cases would be anti patterns like looking up ring
indices directly via the context.
Replace it with a new empty structure, which is just an alias to struct
io_ring_ctx. It'll create a new BTF type and fail verification if a BPF
program tries to access it (beyond the first byte). It'll also give more
flexibility for the future, and otherwise it can be made aligned with
io_ring_ctx as before with struct groups if ever needed or extended in a
different way.
Fixes: d0e437b76bd3c ("io_uring/bpf-ops: implement loop_step with BPF struct_ops")
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://patch.msgid.link/5f6ca3649e9e0bae8667db4357e28dd00cd07901.1780394491.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
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io_uring_enter() and io_uring_register() end up having duplicated code
for getting a ctx from a passed in file descriptor, for either a
registered ring descriptor or a normal file descriptor. Move the
io_uring_register_get_file() into io_uring.c and name it a bit more
generically, and use it from both callsites rather than have that logic
and handling duplicated.
Signed-off-by: Jens Axboe <axboe@kernel.dk>
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Implement BPF struct ops registration. It's registered off the BPF
path, and can be removed by BPF as well as io_uring. To protect it,
introduce a global lock synchronising registration. ctx->uring_lock can
be nested under it. ctx->bpf_ops is write protected by both locks and
so it's safe to read it under either of them.
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://patch.msgid.link/1f46bffd76008de49cbafa2ad77d348810a4f69e.1772109579.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
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Add two kfuncs that should cover most of the needs:
1. bpf_io_uring_submit_sqes(), which allows to submit io_uring requests.
It mirrors the normal user space submission path and follows all
related io_uring_enter(2) rules. i.e. SQEs are taken from the SQ
according to head/tail values. In case of IORING_SETUP_SQ_REWIND,
it'll submit first N entries.
2. bpf_io_uring_get_region() returns a pointer to the specified region,
where io_uring regions are kernel-userspace shared chunks of memory.
It takes the size as an argument, which should be a load time
constant. There are 3 types of regions:
- IOU_REGION_SQ returns the submission queue.
- IOU_REGION_CQ stores the CQ, SQ/CQ headers and the sqarray. In
other words, it gives same memory that would normally be mmap'ed
with IORING_FEAT_SINGLE_MMAP enabled IORING_OFF_SQ_RING.
- IOU_REGION_MEM represents the memory / parameter region. It can be
used to store request indirect parameters and for kernel - user
communication.
It intentionally provides a thin but flexible API and expects BPF
programs to implement CQ/SQ header parsing, CQ walking, etc. That
mirrors how the normal user space works with rings and should help
to minimise kernel / kfunc helpers changes while introducing new generic
io_uring features.
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://patch.msgid.link/967bcc10e94c796eb273998621551b2a21848cde.1772109579.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
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Introduce io_uring BPF struct ops implementing the loop_step callback,
which will allow BPF to overwrite the default io_uring event loop logic.
The callback takes an io_uring context, the main role of which is to be
passed to io_uring kfuncs. The other argument is a struct iou_loop_params,
which BPF can use to request CQ waiting and communicate other parameters.
See the event loop description in the previous patch for more details.
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://patch.msgid.link/98db437651ce64e9cbeb611c60bf5887259db09f.1772109579.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
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