kernel/linux.git/io_uring/register.c, branch v6.18.21

io_uring: ensure ctx->rings is stable for task work flags manipulation

2026-03-19T15:08:51+00:00

Commit 96189080265e6bb5dde3a4afbaf947af493e3f82 upstream. If DEFER_TASKRUN | SETUP_TASKRUN is used and task work is added while the ring is being resized, it's possible for the OR'ing of IORING_SQ_TASKRUN to happen in the small window of swapping into the new rings and the old rings being freed. Prevent this by adding a 2nd ->rings pointer, ->rings_rcu, which is protected by RCU. The task work flags manipulation is inside RCU already, and if the resize ring freeing is done post an RCU synchronize, then there's no need to add locking to the fast path of task work additions. Note: this is only done for DEFER_TASKRUN, as that's the only setup mode that supports ring resizing. If this ever changes, then they too need to use the io_ctx_mark_taskrun() helper. Link: https://lore.kernel.org/io-uring/20260309062759.482210-1-naup96721@gmail.com/ Cc: stable@vger.kernel.org Fixes: 79cfe9e59c2a ("io_uring/register: add IORING_REGISTER_RESIZE_RINGS") Reported-by: Hao-Yu Yang Suggested-by: Pavel Begunkov Signed-off-by: Jens Axboe Signed-off-by: Greg Kroah-Hartman

io_uring: use release-acquire ordering for IORING_SETUP_R_DISABLED

2026-02-26T22:58:59+00:00

[ Upstream commit 7a8737e1132ff07ca225aa7a4008f87319b5b1ca ] io_uring_enter(), __io_msg_ring_data(), and io_msg_send_fd() read ctx->flags and ctx->submitter_task without holding the ctx's uring_lock. This means they may race with the assignment to ctx->submitter_task and the clearing of IORING_SETUP_R_DISABLED from ctx->flags in io_register_enable_rings(). Ensure the correct ordering of the ctx->flags and ctx->submitter_task memory accesses by storing to ctx->flags using release ordering and loading it using acquire ordering. Signed-off-by: Caleb Sander Mateos Fixes: 4add705e4eeb ("io_uring: remove io_register_submitter") Reviewed-by: Joanne Koong Reviewed-by: Gabriel Krisman Bertazi Signed-off-by: Jens Axboe Signed-off-by: Sasha Levin

io_uring/zcrx: remove sync refill uapi

2025-11-03T15:55:58+00:00

There is a better way to handle the problem IORING_REGISTER_ZCRX_REFILL solves. The uapi can also be slightly adjusted to accommodate future extensions. Remove the feature for now, it'll be reworked for the next release. Signed-off-by: Pavel Begunkov Signed-off-by: Jens Axboe

io_uring: fix unexpected placement on same size resizing

2025-10-15T14:01:38+00:00

There might be many reasons why a user is resizing a ring, e.g. moving to huge pages or for some memory compaction using IORING_SETUP_NO_MMAP. Don't bypass resizing, the user will definitely be surprised seeing 0 while the rings weren't actually moved to a new place. Signed-off-by: Pavel Begunkov Signed-off-by: Jens Axboe

io_uring: protect mem region deregistration

2025-10-15T14:01:09+00:00

io_create_region_mmap_safe() protects publishing of a region against concurrent mmap calls, however we should also protect against it when removing a region. There is a gap io_register_mem_region() where it safely publishes a region, but then copy_to_user goes wrong and it unsafely frees the region. Cc: stable@vger.kernel.org Fixes: 087f997870a94 ("io_uring/memmap: implement mmap for regions") Signed-off-by: Pavel Begunkov Signed-off-by: Jens Axboe

io_uring/zcrx: allow synchronous buffer return

2025-09-16T18:37:21+00:00

Returning buffers via a ring is performant and convenient, but it becomes a problem when/if the user misconfigured the ring size and it becomes full. Add a synchronous way to return buffers back to the page pool via a new register opcode. It's supposed to be a reliable slow path for refilling. Signed-off-by: Pavel Begunkov Signed-off-by: Jens Axboe

io_uring: don't include filetable.h in io_uring.h

2025-09-08T19:20:46+00:00

io_uring/io_uring.h doesn't use anything declared in io_uring/filetable.h, so drop the unnecessary #include. Add filetable.h includes in .c files previously relying on the transitive include from io_uring.h. Signed-off-by: Caleb Sander Mateos Signed-off-by: Jens Axboe

io_uring: Replace kzalloc() + copy_from_user() with memdup_user()

2025-09-08T14:21:36+00:00

Replace kzalloc() followed by copy_from_user() with memdup_user() to improve and simplify io_probe(). No functional changes intended. Signed-off-by: Thorsten Blum Signed-off-by: Jens Axboe

io_uring: introduce io_uring querying

2025-09-08T14:06:37+00:00

There are many parameters users might want to query about io_uring like available request types or the ring sizes. This patch introduces an interface for such slow path queries. It was written with several requirements in mind: - Can be used with or without an io_uring instance. Asking for supported setup flags before creating an instance as well as qeurying info about an already created ring are valid use cases. - Should be moderately fast. For example, users might use it to periodically retrieve ring attributes at runtime. As a consequence, it should be able to query multiple attributes in a single syscall. - Backward and forward compatible. - Should be reasobably easy to use. - Reduce the kernel code size for introducing new query types. It's implemented as a new registration opcode IORING_REGISTER_QUERY. The user passes one or more query strutctures linked together, each represented by struct io_uring_query_hdr. The header stores common control fields needed for processing and points to query type specific information. The header contains - The query type - The result field, which on return contains the error code for the query - Pointer to the query type specific information - The size of the query structure. The kernel will only populate up to the size, which helps with backward compatibility. The kernel can also reduce the size, so if the current kernel is older than the inteface the user tries to use, it'll get only the supported bits. - next_entry field is used to chain multiple queries. Apart from common registeration syscall failures, it can only immediately return an error code in case when the headers are incorrect or any other addresses and invalid. That usually mean that the userspace doesn't use the API right and should be corrected. All query type specific errors are returned in the header's result field. As an example, the patch adds a single query type for now, i.e. IO_URING_QUERY_OPCODES, which tells what register / request / etc. opcodes are supported, but there are particular plans to extend it. Note: there is a request probing interface via IORING_REGISTER_PROBE, but it's a mess. It requires the user to create a ring first, it only works for requests, and requires dynamic allocations. Reviewed-by: Martin K. Petersen Signed-off-by: Pavel Begunkov Signed-off-by: Jens Axboe

io_uring: add helper for *REGISTER_SEND_MSG_RING

2025-09-08T14:06:37+00:00

Move handling of IORING_REGISTER_SEND_MSG_RING into a separate function in preparation to growing io_uring_register_blind(). Signed-off-by: Pavel Begunkov Reviewed-by: Martin K. Petersen Signed-off-by: Jens Axboe