linux-kernel - [PATCH 4.9 019/125] usb: gadget: f_fs: Fix use after free issue as part of queue failure

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Date:   Wed, 22 Apr 2020 11:55:36 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Sriharsha Allenki <sallenki@...eaurora.org>,
        Peter Chen <peter.chen@....com>
Subject: [PATCH 4.9 019/125] usb: gadget: f_fs: Fix use after free issue as part of queue failure

From: Sriharsha Allenki <sallenki@...eaurora.org>

commit f63ec55ff904b2f2e126884fcad93175f16ab4bb upstream.

In AIO case, the request is freed up if ep_queue fails.
However, io_data->req still has the reference to this freed
request. In the case of this failure if there is aio_cancel
call on this io_data it will lead to an invalid dequeue
operation and a potential use after free issue.
Fix this by setting the io_data->req to NULL when the request
is freed as part of queue failure.

Fixes: 2e4c7553cd6f ("usb: gadget: f_fs: add aio support")
Signed-off-by: Sriharsha Allenki <sallenki@...eaurora.org>
CC: stable <stable@...r.kernel.org>
Reviewed-by: Peter Chen <peter.chen@....com>
Link: https://lore.kernel.org/r/20200326115620.12571-1-sallenki@codeaurora.org
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/usb/gadget/function/f_fs.c |    1 +
 1 file changed, 1 insertion(+)

--- a/drivers/usb/gadget/function/f_fs.c
+++ b/drivers/usb/gadget/function/f_fs.c
@@ -1036,6 +1036,7 @@ static ssize_t ffs_epfile_io(struct file
 
 		ret = usb_ep_queue(ep->ep, req, GFP_ATOMIC);
 		if (unlikely(ret)) {
+			io_data->req = NULL;
 			usb_ep_free_request(ep->ep, req);
 			goto error_lock;
 		}