Merge tag 'io_uring-6.6-2023-09-08' of git://git.kernel.dk/linux

Pull io_uring fixes from Jens Axboe:
 "A few fixes that should go into the 6.6-rc merge window:

   - Fix for a regression this merge window caused by the SQPOLL
     affinity patch, where we can race with SQPOLL thread shutdown and
     cause an oops when trying to set affinity (Gabriel)

   - Fix for a regression this merge window where fdinfo reading with
     for a ring setup with IORING_SETUP_NO_SQARRAY will attempt to
     deference the non-existing SQ ring array (me)

   - Add the patch that allows more finegrained control over who can use
     io_uring (Matteo)

   - Locking fix for a regression added this merge window for IOPOLL
     overflow (Pavel)

   - IOPOLL fix for stable, breaking our loop if helper threads are
     exiting (Pavel)

  Also had a fix for unreaped iopoll requests from io-wq from Ming, but
  we found an issue with that and hence it got reverted. Will get this
  sorted for a future rc"

* tag 'io_uring-6.6-2023-09-08' of git://git.kernel.dk/linux:
  Revert "io_uring: fix IO hang in io_wq_put_and_exit from do_exit()"
  io_uring: fix unprotected iopoll overflow
  io_uring: break out of iowq iopoll on teardown
  io_uring: add a sysctl to disable io_uring system-wide
  io_uring/fdinfo: only print ->sq_array[] if it's there
  io_uring: fix IO hang in io_wq_put_and_exit from do_exit()
  io_uring: Don't set affinity on a dying sqpoll thread

1 files changed, 29 insertions, 0 deletions

diff --git a/Documentation/admin-guide/sysctl/kernel.rst b/Documentation/admin-guide/sysctl/kernel.rst
index 8019103aac10..cf33de56da27 100644
--- a/Documentation/admin-guide/sysctl/kernel.rst
+++ b/Documentation/admin-guide/sysctl/kernel.rst
@@ -450,6 +450,35 @@ this allows system administrators to override the
 ``IA64_THREAD_UAC_NOPRINT`` ``prctl`` and avoid logs being flooded.
 
 
+io_uring_disabled
+=================
+
+Prevents all processes from creating new io_uring instances. Enabling this
+shrinks the kernel's attack surface.
+
+= ======================================================================
+0 All processes can create io_uring instances as normal. This is the
+  default setting.
+1 io_uring creation is disabled (io_uring_setup() will fail with
+  -EPERM) for unprivileged processes not in the io_uring_group group.
+  Existing io_uring instances can still be used.  See the
+  documentation for io_uring_group for more information.
+2 io_uring creation is disabled for all processes. io_uring_setup()
+  always fails with -EPERM. Existing io_uring instances can still be
+  used.
+= ======================================================================
+
+
+io_uring_group
+==============
+
+When io_uring_disabled is set to 1, a process must either be
+privileged (CAP_SYS_ADMIN) or be in the io_uring_group group in order
+to create an io_uring instance.  If io_uring_group is set to -1 (the
+default), only processes with the CAP_SYS_ADMIN capability may create
+io_uring instances.
+
+
 kexec_load_disabled
 ===================