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authorJens Axboe <axboe@kernel.dk>2023-06-13 19:26:55 -0600
committerJens Axboe <axboe@kernel.dk>2023-06-14 12:54:55 -0600
commitadeaa3f290ecf7f6a6a5c53219a4686cbdff5fbd (patch)
tree594103ff2751e9f571323f6cd21eb2ab1f757a65
parentcac9e4418f4cbd548ccb065b3adcafe073f7f7d2 (diff)
io_uring/io-wq: clear current->worker_private on exit
A recent fix stopped clearing PF_IO_WORKER from current->flags on exit, which meant that we can now call inc/dec running on the worker after it has been removed if it ends up scheduling in/out as part of exit. If this happens after an RCU grace period has passed, then the struct pointed to by current->worker_private may have been freed, and we can now be accessing memory that is freed. Ensure this doesn't happen by clearing the task worker_private field. Both io_wq_worker_running() and io_wq_worker_sleeping() check this field before going any further, and we don't need any accounting etc done after this worker has exited. Fixes: fd37b884003c ("io_uring/io-wq: don't clear PF_IO_WORKER on exit") Reported-by: Zorro Lang <zlang@redhat.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
-rw-r--r--io_uring/io-wq.c7
1 files changed, 6 insertions, 1 deletions
diff --git a/io_uring/io-wq.c b/io_uring/io-wq.c
index fe38eb0cbc82..399e9a15c38d 100644
--- a/io_uring/io-wq.c
+++ b/io_uring/io-wq.c
@@ -220,7 +220,12 @@ static void io_worker_exit(struct io_worker *worker)
list_del_rcu(&worker->all_list);
raw_spin_unlock(&wq->lock);
io_wq_dec_running(worker);
- worker->flags = 0;
+ /*
+ * this worker is a goner, clear ->worker_private to avoid any
+ * inc/dec running calls that could happen as part of exit from
+ * touching 'worker'.
+ */
+ current->worker_private = NULL;
kfree_rcu(worker, rcu);
io_worker_ref_put(wq);