6.1-stable review patch. If anyone has any objections, please let me know.
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From: Pavel Begunkov asml.silence@gmail.com
commit dbd2ca9367eb19bc5e269b8c58b0b1514ada9156 upstream.
task work can be executed after the task has gone through io_uring termination, whether it's the final task_work run or the fallback path. In this case, task work will find ->io_wq being already killed and null'ed, which is a problem if it then tries to forward the request to io_queue_iowq(). Make io_queue_iowq() fail requests in this case.
Note that it also checks PF_KTHREAD, because the user can first close a DEFER_TASKRUN ring and shortly after kill the task, in which case ->iowq check would race.
Cc: stable@vger.kernel.org Fixes: 50c52250e2d74 ("block: implement async io_uring discard cmd") Fixes: 773af69121ecc ("io_uring: always reissue from task_work context") Reported-by: Will willsroot@protonmail.com Signed-off-by: Pavel Begunkov asml.silence@gmail.com Link: https://lore.kernel.org/r/63312b4a2c2bb67ad67b857d17a300e1d3b078e8.173463790... Signed-off-by: Jens Axboe axboe@kernel.dk Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- io_uring/io_uring.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-)
--- a/io_uring/io_uring.c +++ b/io_uring/io_uring.c @@ -440,7 +440,11 @@ void io_queue_iowq(struct io_kiocb *req, struct io_uring_task *tctx = req->task->io_uring;
BUG_ON(!tctx); - BUG_ON(!tctx->io_wq); + + if ((current->flags & PF_KTHREAD) || !tctx->io_wq) { + io_req_task_queue_fail(req, -ECANCELED); + return; + }
/* init ->work of the whole link before punting */ io_prep_async_link(req);