io-wq: Fix UAF when wakeup wqe in hash waitqueue

BUG: KASAN: use-after-free in __wake_up_common+0x637/0x650
Read of size 8 at addr ffff8880304250d8 by task iou-wrk-28796/28802

Call Trace:
 __dump_stack [inline]
 dump_stack+0x141/0x1d7
 print_address_description.constprop.0.cold+0x5b/0x2c6
 __kasan_report [inline]
 kasan_report.cold+0x7c/0xd8
 __wake_up_common+0x637/0x650
 __wake_up_common_lock+0xd0/0x130
 io_worker_handle_work+0x9dd/0x1790
 io_wqe_worker+0xb2a/0xd40
 ret_from_fork+0x1f/0x30

Allocated by task 28798:
 kzalloc_node [inline]
 io_wq_create+0x3c4/0xdd0
 io_init_wq_offload [inline]
 io_uring_alloc_task_context+0x1bf/0x6b0
 __io_uring_add_task_file+0x29a/0x3c0
 io_uring_add_task_file [inline]
 io_uring_install_fd [inline]
 io_uring_create [inline]
 io_uring_setup+0x209a/0x2bd0
 do_syscall_64+0x3a/0xb0
 entry_SYSCALL_64_after_hwframe+0x44/0xae

Freed by task 28798:
 kfree+0x106/0x2c0
 io_wq_destroy+0x182/0x380
 io_wq_put [inline]
 io_wq_put_and_exit+0x7a/0xa0
 io_uring_clean_tctx [inline]
 __io_uring_cancel+0x428/0x530
 io_uring_files_cancel
 do_exit+0x299/0x2a60
 do_group_exit+0x125/0x310
 get_signal+0x47f/0x2150
 arch_do_signal_or_restart+0x2a8/0x1eb0
 handle_signal_work[inline]
 exit_to_user_mode_loop [inline]
 exit_to_user_mode_prepare+0x171/0x280
 __syscall_exit_to_user_mode_work [inline]
 syscall_exit_to_user_mode+0x19/0x60
 do_syscall_64+0x47/0xb0
 entry_SYSCALL_64_after_hwframe

There are the following scenarios, hash waitqueue is shared by
io-wq1 and io-wq2. (note: wqe is worker)

io-wq1:worker2     | locks bit1
io-wq2:worker1     | waits bit1
io-wq1:worker3     | waits bit1

io-wq1:worker2     | completes all wqe bit1 work items
io-wq1:worker2     | drop bit1, exit

io-wq2:worker1     | locks bit1
io-wq1:worker3     | can not locks bit1, waits bit1 and exit
io-wq1             | exit and free io-wq1
io-wq2:worker1     | drops bit1
io-wq1:worker3     | be waked up, even though wqe is freed

After all iou-wrk belonging to io-wq1 have exited, remove wqe
form hash waitqueue, it is guaranteed that there will be no more
wqe belonging to io-wq1 in the hash waitqueue.

Reported-by: syzbot+6cb11ade52aa17095297@syzkaller.appspotmail.com
Signed-off-by: Zqiang <qiang.zhang@windriver.com>
Link: https://lore.kernel.org/r/20210526050826.30500-1-qiang.zhang@windriver.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/fs/io-wq.c b/fs/io-wq.c
index de9b7ba3ba0151ccc41a94d1d4d57860a1d54e68..b3e8624a37d0904c73151fc00a4b3bb64b60dc70 100644 (file)
--- a/fs/io-wq.c
+++ b/fs/io-wq.c
@@ -1006,13 +1006,16 @@ static void io_wq_exit_workers(struct io_wq *wq)
                struct io_wqe *wqe = wq->wqes[node];
 
                io_wq_for_each_worker(wqe, io_wq_worker_wake, NULL);
-               spin_lock_irq(&wq->hash->wait.lock);
-               list_del_init(&wq->wqes[node]->wait.entry);
-               spin_unlock_irq(&wq->hash->wait.lock);
        }
        rcu_read_unlock();
        io_worker_ref_put(wq);
        wait_for_completion(&wq->worker_done);
+
+       for_each_node(node) {
+               spin_lock_irq(&wq->hash->wait.lock);
+               list_del_init(&wq->wqes[node]->wait.entry);
+               spin_unlock_irq(&wq->hash->wait.lock);
+       }
        put_task_struct(wq->task);
        wq->task = NULL;
 }