From 8c9cb6cd9a46ae6fb7cb6c39cf6a48a53440feef Mon Sep 17 00:00:00 2001 From: Pavel Begunkov Date: Sun, 28 Jun 2020 12:52:29 +0300 Subject: [PATCH] io_uring: fix refs underflow in io_iopoll_queue() Now io_complete_rw_common() puts a ref, extra io_req_put() in io_iopoll_queue() causes undeflow. Remove it. [ 455.998620] refcount_t: underflow; use-after-free. [ 455.998743] WARNING: CPU: 6 PID: 285394 at lib/refcount.c:28 refcount_warn_saturate+0xae/0xf0 [ 455.998772] CPU: 6 PID: 285394 Comm: read-write2 Tainted: G I E 5.8.0-rc2-00048-g1b1aa738f167-dirty #509 [ 455.998772] RIP: 0010:refcount_warn_saturate+0xae/0xf0 ... [ 455.998778] Call Trace: [ 455.998778] io_put_req+0x44/0x50 [ 455.998778] io_iopoll_complete+0x245/0x370 [ 455.998779] io_iopoll_getevents+0x12f/0x1a0 [ 455.998779] io_iopoll_reap_events.part.0+0x5e/0xa0 [ 455.998780] io_ring_ctx_wait_and_kill+0x132/0x1c0 [ 455.998780] io_uring_release+0x20/0x30 [ 455.998780] __fput+0xcd/0x230 [ 455.998781] ____fput+0xe/0x10 [ 455.998781] task_work_run+0x67/0xa0 [ 455.998781] do_exit+0x35d/0xb70 [ 455.998782] do_group_exit+0x43/0xa0 [ 455.998783] get_signal+0x140/0x900 [ 455.998783] do_signal+0x37/0x780 [ 455.998784] __prepare_exit_to_usermode+0x126/0x1c0 [ 455.998785] __syscall_return_slowpath+0x3b/0x1c0 [ 455.998785] do_syscall_64+0x5f/0xa0 [ 455.998785] entry_SYSCALL_64_after_hwframe+0x44/0xa9 Fixes: a1d7c393c47 ("io_uring: enable READ/WRITE to use deferred completions") Signed-off-by: Pavel Begunkov Signed-off-by: Jens Axboe --- fs/io_uring.c | 1 - 1 file changed, 1 deletion(-) diff --git a/fs/io_uring.c b/fs/io_uring.c index 4a9929c..ab9f2f3 100644 --- a/fs/io_uring.c +++ b/fs/io_uring.c @@ -1904,7 +1904,6 @@ static void io_iopoll_queue(struct list_head *again) /* shouldn't happen unless io_uring is dying, cancel reqs */ if (unlikely(!current->mm)) { io_complete_rw_common(&req->rw.kiocb, -EAGAIN, NULL); - io_put_req(req); continue; } -- 2.7.4