io_uring: fix files cancellation

io_uring_cancel_files()'s task check condition mistakenly got flipped.

1. There can't be a request in the inflight list without
IO_WQ_WORK_FILES, kill this check to keep the whole condition simpler.
2. Also, don't call the function for files==NULL to not do such a check,
all that staff is already handled well by its counter part,
__io_uring_cancel_task_requests().

With that just flip the task check.

Also, it iowq-cancels all request of current task there, don't forget to
set right ->files into struct io_task_cancel.

Fixes: c1973b38bf639 ("io_uring: cancel only requests of current task")
Reported-by: syzbot+c0d52d0b3c0c3ffb9525@syzkaller.appspotmail.com
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

fs/io_uring.c

@@ -8688,15 +8688,14 @@ static void io_uring_cancel_files(struct io_ring_ctx *ctx,
 				  struct files_struct *files)
 {
 	while (!list_empty_careful(&ctx->inflight_list)) {
-		struct io_task_cancel cancel = { .task = task, .files = NULL, };
+		struct io_task_cancel cancel = { .task = task, .files = files };
 		struct io_kiocb *req;
 		DEFINE_WAIT(wait);
 		bool found = false;
 
 		spin_lock_irq(&ctx->inflight_lock);
 		list_for_each_entry(req, &ctx->inflight_list, inflight_entry) {
-			if (req->task == task &&
-			    (req->work.flags & IO_WQ_WORK_FILES) &&
+			if (req->task != task ||
 			    req->work.identity->files != files)
 				continue;
 			found = true;
@@ -8768,10 +8767,11 @@ static void io_uring_cancel_task_requests(struct io_ring_ctx *ctx,
 
 	io_cancel_defer_files(ctx, task, files);
 	io_cqring_overflow_flush(ctx, true, task, files);
-	io_uring_cancel_files(ctx, task, files);
 
 	if (!files)
 		__io_uring_cancel_task_requests(ctx, task);
+	else
+		io_uring_cancel_files(ctx, task, files);
 
 	if ((ctx->flags & IORING_SETUP_SQPOLL) && ctx->sq_data) {
 		atomic_dec(&task->io_uring->in_idle);