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  1. 27 5月, 2021 1 次提交
    • M
      io_uring: fix data race to avoid potential NULL-deref · b16ef427
      由 Marco Elver 提交于 
      Commit ba5ef6dc ("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: ba5ef6dc ("io_uring: fortify tctx/io_wq cleanup")
Suggested-by: NPavel Begunkov <asml.silence@gmail.com>
Reported-by: syzbot+bf2b3d0435b9b728946c@syzkaller.appspotmail.com
Signed-off-by: NMarco Elver <elver@google.com>
Cc: Jens Axboe <axboe@kernel.dk>
Link: https://lore.kernel.org/r/20210527092547.2656514-1-elver@google.comSigned-off-by: NJens Axboe <axboe@kernel.dk>
      b16ef427
  3. 26 5月, 2021 1 次提交
    • P
      io_uring/io-wq: close io-wq full-stop gap · 17a91051
      由 Pavel Begunkov 提交于 
      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: NPavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/abfcf8c54cb9e8f7bfbad7e9a0cc5433cc70bdc2.1621781238.git.asml.silence@gmail.comSigned-off-by: NJens Axboe <axboe@kernel.dk>
      17a91051
  5. 20 5月, 2021 1 次提交
  7. 17 5月, 2021 1 次提交
  9. 14 5月, 2021 3 次提交
  11. 09 5月, 2021 1 次提交
    • P
      io_uring: fix link timeout refs · a298232e
      由 Pavel Begunkov 提交于 
      WARNING: CPU: 0 PID: 10242 at lib/refcount.c:28 refcount_warn_saturate+0x15b/0x1a0 lib/refcount.c:28
RIP: 0010:refcount_warn_saturate+0x15b/0x1a0 lib/refcount.c:28
Call Trace:
 __refcount_sub_and_test include/linux/refcount.h:283 [inline]
 __refcount_dec_and_test include/linux/refcount.h:315 [inline]
 refcount_dec_and_test include/linux/refcount.h:333 [inline]
 io_put_req fs/io_uring.c:2140 [inline]
 io_queue_linked_timeout fs/io_uring.c:6300 [inline]
 __io_queue_sqe+0xbef/0xec0 fs/io_uring.c:6354
 io_submit_sqe fs/io_uring.c:6534 [inline]
 io_submit_sqes+0x2bbd/0x7c50 fs/io_uring.c:6660
 __do_sys_io_uring_enter fs/io_uring.c:9240 [inline]
 __se_sys_io_uring_enter+0x256/0x1d60 fs/io_uring.c:9182

io_link_timeout_fn() should put only one reference of the linked timeout
request, however in case of racing with the master request's completion
first io_req_complete() puts one and then io_put_req_deferred() is
called.

Cc: stable@vger.kernel.org # 5.12+
Fixes: 9ae1f8dd ("io_uring: fix inconsistent lock state")
Reported-by: syzbot+a2910119328ce8e7996f@syzkaller.appspotmail.com
Signed-off-by: NPavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/ff51018ff29de5ffa76f09273ef48cb24c720368.1620417627.git.asml.silence@gmail.comSigned-off-by: NJens Axboe <axboe@kernel.dk>
      a298232e
  13. 06 5月, 2021 1 次提交
  15. 30 4月, 2021 7 次提交
  17. 27 4月, 2021 2 次提交
    • H
      io_uring: maintain drain logic for multishot poll requests · 7b289c38
      由 Hao Xu 提交于 
      Now that we have multishot poll requests, one SQE can emit multiple
CQEs. given below example:
    sqe0(multishot poll)-->sqe1-->sqe2(drain req)
sqe2 is designed to issue after sqe0 and sqe1 completed, but since sqe0
is a multishot poll request, sqe2 may be issued after sqe0's event
triggered twice before sqe1 completed. This isn't what users leverage
drain requests for.
Here the solution is to wait for multishot poll requests fully
completed.
To achieve this, we should reconsider the req_need_defer equation, the
original one is:

    all_sqes(excluding dropped ones) == all_cqes(including dropped ones)

This means we issue a drain request when all the previous submitted
SQEs have generated their CQEs.
Now we should consider multishot requests, we deduct all the multishot
CQEs except the cancellation one, In this way a multishot poll request
behave like a normal request, so:
    all_sqes == all_cqes - multishot_cqes(except cancellations)

Here we introduce cq_extra for it.
Signed-off-by: NHao Xu <haoxu@linux.alibaba.com>
Link: https://lore.kernel.org/r/1618298439-136286-1-git-send-email-haoxu@linux.alibaba.comSigned-off-by: NJens Axboe <axboe@kernel.dk>
      7b289c38
    • P
      io_uring: Check current->io_uring in io_uring_cancel_sqpoll · 6d042ffb
      由 Palash Oswal 提交于 
      syzkaller identified KASAN: null-ptr-deref Write in
io_uring_cancel_sqpoll.

io_uring_cancel_sqpoll is called by io_sq_thread before calling
io_uring_alloc_task_context. This leads to current->io_uring being NULL.
io_uring_cancel_sqpoll should not have to deal with threads where
current->io_uring is NULL.

In order to cast a wider safety net, perform input sanitisation directly
in io_uring_cancel_sqpoll and return for NULL value of current->io_uring.
This is safe since if current->io_uring isn't set, then there's no way
for the task to have submitted any requests.

Reported-by: syzbot+be51ca5a4d97f017cd50@syzkaller.appspotmail.com
Cc: stable@vger.kernel.org
Signed-off-by: NPalash Oswal <hello@oswalpalash.com>
Link: https://lore.kernel.org/r/20210427125148.21816-1-hello@oswalpalash.comSigned-off-by: NJens Axboe <axboe@kernel.dk>
      6d042ffb
  19. 26 4月, 2021 19 次提交
  21. 23 4月, 2021 1 次提交
  23. 21 4月, 2021 2 次提交