linux.git/fs/io_uring.c, branch v5.13

io_uring: add feature flag for rsrc tags

2021-06-10T22:33:51+00:00

Add IORING_FEAT_RSRC_TAGS indicating that io_uring supports a bunch of
new IORING_REGISTER operations, in particular
IORING_REGISTER_[FILES[,UPDATE]2,BUFFERS[2,UPDATE]] that support rsrc
tagging, and also indicating implemented dynamic fixed buffer updates.

Signed-off-by: Pavel Begunkov 
Link: https://lore.kernel.org/r/9b995d4045b6c6b4ab7510ca124fd25ac2203af7.1623339162.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe

io_uring: change registration/upd/rsrc tagging ABI

2021-06-10T22:33:51+00:00

There are ABI moments about recently added rsrc registration/update and
tagging that might become a nuisance in the future. First,
IORING_REGISTER_RSRC[_UPD] hide different types of resources under it,
so breaks fine control over them by restrictions. It works for now, but
once those are wanted under restrictions it would require a rework.

It was also inconvenient trying to fit a new resource not supporting
all the features (e.g. dynamic update) into the interface, so better
to return to IORING_REGISTER_* top level dispatching.

Second, register/update were considered to accept a type of resource,
however that's not a good idea because there might be several ways of
registration of a single resource type, e.g. we may want to add
non-contig buffers or anything more exquisite as dma mapped memory.
So, remove IORING_RSRC_[FILE,BUFFER] out of the ABI, and place them
internally for now to limit changes.

Signed-off-by: Pavel Begunkov 
Link: https://lore.kernel.org/r/9b554897a7c17ad6e3becc48dfed2f7af9f423d5.1623339162.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe

io_uring: fix misaccounting fix buf pinned pages

2021-05-30T01:27:21+00:00

As Andres reports "... io_sqe_buffer_register() doesn't initialize imu.
io_buffer_account_pin() does imu->acct_pages++, before calling
io_account_mem(ctx, imu->acct_pages).", leading to evevntual -ENOMEM.

Initialise the field.

Reported-by: Andres Freund 
Fixes: 41edf1a5ec967 ("io_uring: keep table of pointers to ubufs")
Signed-off-by: Pavel Begunkov 
Link: https://lore.kernel.org/r/438a6f46739ae5e05d9c75a0c8fa235320ff367c.1622285901.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe

io_uring: fix data race to avoid potential NULL-deref

2021-05-27T13:44:49+00:00

Commit ba5ef6dc8a82 ("io_uring: fortify tctx/io_wq cleanup") introduced
setting tctx->io_wq to NULL a bit earlier. This has caused KCSAN to
detect a data race between accesses to tctx->io_wq:

  write to 0xffff88811d8df330 of 8 bytes by task 3709 on cpu 1:
   io_uring_clean_tctx                  fs/io_uring.c:9042 [inline]
   __io_uring_cancel                    fs/io_uring.c:9136
   io_uring_files_cancel                include/linux/io_uring.h:16 [inline]
   do_exit                              kernel/exit.c:781
   do_group_exit                        kernel/exit.c:923
   get_signal                           kernel/signal.c:2835
   arch_do_signal_or_restart            arch/x86/kernel/signal.c:789
   handle_signal_work                   kernel/entry/common.c:147 [inline]
   exit_to_user_mode_loop               kernel/entry/common.c:171 [inline]
   ...
  read to 0xffff88811d8df330 of 8 bytes by task 6412 on cpu 0:
   io_uring_try_cancel_iowq             fs/io_uring.c:8911 [inline]
   io_uring_try_cancel_requests         fs/io_uring.c:8933
   io_ring_exit_work                    fs/io_uring.c:8736
   process_one_work                     kernel/workqueue.c:2276
   ...

With the config used, KCSAN only reports data races with value changes:
this implies that in the case here we also know that tctx->io_wq was
non-NULL. Therefore, depending on interleaving, we may end up with:

              [CPU 0]                 |        [CPU 1]
  io_uring_try_cancel_iowq()          | io_uring_clean_tctx()
    if (!tctx->io_wq) // false        |   ...
    ...                               |   tctx->io_wq = NULL
    io_wq_cancel_cb(tctx->io_wq, ...) |   ...
      -> NULL-deref                   |

Note: It is likely that thus far we've gotten lucky and the compiler
optimizes the double-read into a single read into a register -- but this
is never guaranteed, and can easily change with a different config!

Fix the data race by restoring the previous behaviour, where both
setting io_wq to NULL and put of the wq are _serialized_ after
concurrent io_uring_try_cancel_iowq() via acquisition of the uring_lock
and removal of the node in io_uring_del_task_file().

Fixes: ba5ef6dc8a82 ("io_uring: fortify tctx/io_wq cleanup")
Suggested-by: Pavel Begunkov 
Reported-by: syzbot+bf2b3d0435b9b728946c@syzkaller.appspotmail.com
Signed-off-by: Marco Elver 
Cc: Jens Axboe 
Link: https://lore.kernel.org/r/20210527092547.2656514-1-elver@google.com
Signed-off-by: Jens Axboe

io_uring/io-wq: close io-wq full-stop gap

2021-05-26T01:39:58+00:00

There is an old problem with io-wq cancellation where requests should be
killed and are in io-wq but are not discoverable, e.g. in @next_hashed
or @linked vars of io_worker_handle_work(). It adds some unreliability
to individual request canellation, but also may potentially get
__io_uring_cancel() stuck. For instance:

1) An __io_uring_cancel()'s cancellation round have not found any
   request but there are some as desribed.
2) __io_uring_cancel() goes to sleep
3) Then workers wake up and try to execute those hidden requests
   that happen to be unbound.

As we already cancel all requests of io-wq there, set IO_WQ_BIT_EXIT
in advance, so preventing 3) from executing unbound requests. The
workers will initially break looping because of getting a signal as they
are threads of the dying/exec()'ing user task.

Cc: stable@vger.kernel.org
Signed-off-by: Pavel Begunkov 
Link: https://lore.kernel.org/r/abfcf8c54cb9e8f7bfbad7e9a0cc5433cc70bdc2.1621781238.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe

io_uring: fortify tctx/io_wq cleanup

2021-05-20T13:29:11+00:00

We don't want anyone poking into tctx->io_wq awhile it's being destroyed
by io_wq_put_and_exit(), and even though it shouldn't even happen, if
buggy would be preferable to get a NULL-deref instead of subtle delayed
failure or UAF.

Signed-off-by: Pavel Begunkov 
Link: https://lore.kernel.org/r/827b021de17926fd807610b3e53a5a5fa8530856.1621513214.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe

io_uring: don't modify req->poll for rw

2021-05-17T13:28:48+00:00

__io_queue_proc() is used by both poll and apoll, so we should not
access req->poll directly but selecting right struct io_poll_iocb
depending on use case.

Reported-and-tested-by: syzbot+a84b8783366ecb1c65d0@syzkaller.appspotmail.com
Fixes: ea6a693d862d ("io_uring: disable multishot poll for double poll add cases")
Signed-off-by: Pavel Begunkov 
Link: https://lore.kernel.org/r/4a6a1de31142d8e0250fe2dfd4c8923d82a5bbfc.1621251795.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe

io_uring: increase max number of reg buffers

2021-05-14T12:06:34+00:00

Since recent changes instead of storing a large array of struct
io_mapped_ubuf, we store pointers to them, that is 4 times slimmer and
we should not to so worry about restricting max number of registererd
buffer slots, increase the limit 4 times.

Signed-off-by: Pavel Begunkov 
Link: https://lore.kernel.org/r/d3dee1da37f46da416aa96a16bf9e5094e10584d.1620990371.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe

io_uring: further remove sqpoll limits on opcodes

2021-05-14T12:06:23+00:00

There are three types of requests that left disabled for sqpoll, namely
epoll ctx, statx, and resources update. Since SQPOLL task is now closely
mimics a userspace thread, remove the restrictions.

Signed-off-by: Pavel Begunkov 
Link: https://lore.kernel.org/r/909b52d70c45636d8d7897582474ea5aab5eed34.1620990306.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe

io_uring: fix ltout double free on completion race

2021-05-14T12:06:15+00:00

Always remove linked timeout on io_link_timeout_fn() from the master
request link list, otherwise we may get use-after-free when first
io_link_timeout_fn() puts linked timeout in the fail path, and then
will be found and put on master's free.

Cc: stable@vger.kernel.org # 5.10+
Fixes: 90cd7e424969d ("io_uring: track link timeout's master explicitly")
Reported-and-tested-by: syzbot+5a864149dd970b546223@syzkaller.appspotmail.com
Signed-off-by: Pavel Begunkov 
Link: https://lore.kernel.org/r/69c46bf6ce37fec4fdcd98f0882e18eb07ce693a.1620990121.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe