io_uring/waitid: avoid siginfo copy during ring teardown

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>

0 files changed, 0 insertions, 0 deletions