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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org,
        syzbot+27c12725d8ff0bfe1a13@syzkaller.appspotmail.com,
        "Matthew Wilcox (Oracle)" <willy@infradead.org>,
        Jens Axboe <axboe@kernel.dk>
Subject: [PATCH 5.8 14/70] io_uring: Fix use of XArray in __io_uring_files_cancel
Date:   Sat, 31 Oct 2020 12:35:46 +0100
Message-Id: <20201031113500.188798721@linuxfoundation.org>
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From: "Matthew Wilcox (Oracle)" <willy@infradead.org>

commit ce765372bc443573d1d339a2bf4995de385dea3a upstream.

We have to drop the lock during each iteration, so there's no advantage
to using the advanced API.  Convert this to a standard xa_for_each() loop.

Reported-by: syzbot+27c12725d8ff0bfe1a13@syzkaller.appspotmail.com
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 fs/io_uring.c |   19 +++++--------------
 1 file changed, 5 insertions(+), 14 deletions(-)

--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -8008,28 +8008,19 @@ static void io_uring_attempt_task_drop(s
 void __io_uring_files_cancel(struct files_struct *files)
 {
 	struct io_uring_task *tctx = current->io_uring;
-	XA_STATE(xas, &tctx->xa, 0);
+	struct file *file;
+	unsigned long index;
 
 	/* make sure overflow events are dropped */
 	tctx->in_idle = true;
 
-	do {
-		struct io_ring_ctx *ctx;
-		struct file *file;
-
-		xas_lock(&xas);
-		file = xas_next_entry(&xas, ULONG_MAX);
-		xas_unlock(&xas);
-
-		if (!file)
-			break;
-
-		ctx = file->private_data;
+	xa_for_each(&tctx->xa, index, file) {
+		struct io_ring_ctx *ctx = file->private_data;
 
 		io_uring_cancel_task_requests(ctx, files);
 		if (files)
 			io_uring_del_task_file(file);
-	} while (1);
+	}
 }
 
 static inline bool io_uring_task_idle(struct io_uring_task *tctx)