commit 2cf20c4e0f72d523b8673053e7120d092ff1f074 upstream.

During ring teardown, io_ring_exit_work() cancels outstanding requests
from a kworker with a NULL tctx. The waitid cancellation path eventually
reaches io_waitid_finish(), which copies the stored siginfo to the
userspace pointer supplied with the request.

Ring-wide teardown does not run in the task context that submitted the
request, so it must not access that task's userspace pointer. Depending
on the address and mm state, the copy may fail with -EFAULT, but the
uaccess itself is inappropriate from the teardown kworker.

Use a no-copy cancellation callback when io_waitid_remove_all() is
called without an owning task context. Complete the request with
-ECANCELED while releasing the waitid state without touching siginfo.

Keep the existing siginfo handling for explicit async cancellation and
task-scoped cancellation.

Fixes: f31ecf671ddc ("io_uring: add IORING_OP_WAITID support")
Cc: stable@vger.kernel.org
Signed-off-by: Hui Su <sh_def@163.com>
Link: https://patch.msgid.link/20260818103336.1922818-3-sh_def@163.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

commit 14572de82e5022899e5856008bc9cac97004a88c upstream.

io_waitid_cb() may run through the fallback task_work path when
task_work_add() can no longer queue work to the originating task. The
fallback runs from a kworker and io_uring marks such task work as
canceled through tw.cancel.

io_waitid_cb() currently ignores tw.cancel and calls __do_wait().
waitid is task-context dependent: __do_wait() performs child lookup
relative to current, and the retry path also uses
current->signal->wait_chldexit. If the callback runs from the fallback
kworker, current is therefore not the task that submitted the request.

Honor tw.cancel before entering __do_wait(). Complete the request with
-ECANCELED and skip the siginfo copy, since canceled task work may run
without the submitting task's userspace execution context.

Keep the existing siginfo handling for normal waitid completion and
explicit cancellation.

Fixes: f31ecf671ddc ("io_uring: add IORING_OP_WAITID support")
Cc: stable@vger.kernel.org
Signed-off-by: Hui Su <sh_def@163.com>
Link: https://patch.msgid.link/20260818103336.1922818-2-sh_def@163.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

commit cd305ee3633a45fcf5f3a5d83f99f3cb77d87b6e upstream.

io_req_local_work_add() signals the CQ ring eventfd inline when it is the
one to push the first entry onto ->work_list. For DEFER_TASKRUN rings that
add is frequently done from a waitqueue wakeup handler, where an
arbitrary waitqueue lock is held.

eventfd_signal_mask() only refuses to recurse when current->in_eventfd
is set, but that bit is set by eventfd_signal_mask() itself. If the wake
chain starts somewhere else, signal goes out inline and can feed back
into epoll.

Add IOU_F_TWQ_IN_WAKE, set it on the task_work add done from the three
waitqueue callbacks, and use it to force io_eventfd_signal() down the
existing call_rcu_hurry() deferral instead of signaling inline.

Fixes: 21a091b970cd ("io_uring: signal registered eventfd to process deferred task work")
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/all/20260813133843.2933127-1-4ncienth@gmail.com/
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

IORING_OP_WAITID stores its result fields in struct io_waitid::info and
later copies them to userspace siginfo. The prep path initializes the
request arguments, but it does not initialize info itself.

If the wait operation completes without reporting a child event, the common
wait code can return without writing wo_info. In that case io_waitid_finish()
still copies iw->info to userspace, exposing stale bytes from the reused
io_kiocb command storage.

Clear the result storage during prep so the io_uring path matches the
regular waitid syscall, which uses a zero-initialized struct waitid_info.

Fixes: f31ecf671ddc ("io_uring: add IORING_OP_WAITID support")
Cc: stable@vger.kernel.org # 6.7+
Signed-off-by: Heechan Kang <gganji11@naver.com>
Link: https://patch.msgid.link/20260516184709.852814-1-gganji11@naver.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Storing of the iw->head entry inside the wait_queue callback, or when
removing a waitid item, really should use proper load/store
acquire/release semantics, and KCSAN correctly warns of that. Ensure
that they do so.

Reported-by: syzbot+eb441775f4f948a0902f@syzkaller.appspotmail.com
Fixes: a48c0cbf28c0 ("io_uring/waitid: have io_waitid_complete() remove wait queue entry")
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Merge 6.18-rc io_uring fixes, as certain coming changes depend on some
of these.

* io_uring-6.18:
  io_uring/rsrc: don't use blk_rq_nr_phys_segments() as number of bvecs
  io_uring/query: return number of available queries
  io_uring/rw: ensure allocated iovec gets cleared for early failure
  io_uring: fix regbuf vector size truncation
  io_uring: fix types for region size calulation
  io_uring/zcrx: remove sync refill uapi
  io_uring: fix buffer auto-commit for multishot uring_cmd
  io_uring: correct __must_hold annotation in io_install_fixed_file
  io_uring zcrx: add MAINTAINERS entry
  io_uring: Fix code indentation error
  io_uring/sqpoll: be smarter on when to update the stime usage
  io_uring/sqpoll: switch away from getrusage() for CPU accounting
  io_uring: fix incorrect unlikely() usage in io_waitid_prep()

Signed-off-by: Jens Axboe <axboe@kernel.dk>

In preparation for uring_cmd implementations to implement functions
with the io_req_tw_func_t signature, introduce a wrapper struct
io_tw_req to hide the struct io_kiocb * argument. The intention is for
only the io_uring core to access the inner struct io_kiocb *. uring_cmd
implementations should instead call a helper from io_uring/cmd.h to
convert struct io_tw_req to struct io_uring_cmd *.

Signed-off-by: Caleb Sander Mateos <csander@purestorage.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Use it everywhere that the wait_queue_entry is removed from the head,
and be a bit more cautious in zeroing out iw->head whenever the entry is
removed from the list.

Signed-off-by: Jens Axboe <axboe@kernel.dk>

Both callers of this need the entry potentially removed, so shift the
removal into the completion side and kill it from the two callers.

While at it, add a helper for removing the wait_queue_entry based
on the passed in io_kiocb.

Signed-off-by: Jens Axboe <axboe@kernel.dk>

The negation operator is incorrectly placed outside the unlikely()
macro:

    if (!unlikely(iwa))

This inverts the compiler branch prediction hint, marking the NULL case
as likely instead of unlikely. The intent is to indicate that allocation
failures are rare, consistent with common kernel patterns.

 Moving the negation inside unlikely():

    if (unlikely(!iwa))

Fixes: 2b4fc4cd43f2 ("io_uring/waitid: setup async data in the prep handler")
Signed-off-by: Alok Tiwari <alok.a.tiwari@oracle.com>
Reviewed-by: Gabriel Krisman Bertazi <krisman@suse.de>
Reviewed-by: Caleb Sander Mateos <csander@purestorage.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>