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From: Kamal Mostafa <kamal@canonical.com>
To: linux-kernel@vger.kernel.org, stable@vger.kernel.org,
        kernel-team@lists.ubuntu.com
Cc: Jiri Slaby <jslaby@suse.cz>, Marcel Holtmann <marcel@holtmann.org>,
        Kamal Mostafa <kamal@canonical.com>
Subject: [PATCH 4.2.y-ckt 014/206] Bluetooth: vhci: purge unhandled skbs
Date: Thu,  9 Jun 2016 14:13:43 -0700
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4.2.8-ckt12 -stable review patch.  If anyone has any objections, please let me know.

---8<------------------------------------------------------------

From: Jiri Slaby <jslaby@suse.cz>

commit 13407376b255325fa817798800117a839f3aa055 upstream.

The write handler allocates skbs and queues them into data->readq.
Read side should read them, if there is any. If there is none, skbs
should be dropped by hdev->flush. But this happens only if the device
is HCI_UP, i.e. hdev->power_on work was triggered already. When it was
not, skbs stay allocated in the queue when /dev/vhci is closed. So
purge the queue in ->release.

Program to reproduce:
	#include <err.h>
	#include <fcntl.h>
	#include <stdio.h>
	#include <unistd.h>

	#include <sys/stat.h>
	#include <sys/types.h>
	#include <sys/uio.h>

	int main()
	{
		char buf[] = { 0xff, 0 };
		struct iovec iov = {
			.iov_base = buf,
			.iov_len = sizeof(buf),
		};
		int fd;

		while (1) {
			fd = open("/dev/vhci", O_RDWR);
			if (fd < 0)
				err(1, "open");

			usleep(50);

			if (writev(fd, &iov, 1) < 0)
				err(1, "writev");

			usleep(50);

			close(fd);
		}

		return 0;
	}

Result:
kmemleak: 4609 new suspected memory leaks
unreferenced object 0xffff88059f4d5440 (size 232):
  comm "vhci", pid 1084, jiffies 4294912542 (age 37569.296s)
  hex dump (first 32 bytes):
    20 f0 23 87 05 88 ff ff 20 f0 23 87 05 88 ff ff   .#..... .#.....
    00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
  backtrace:
...
    [<ffffffff81ece010>] __alloc_skb+0x0/0x5a0
    [<ffffffffa021886c>] vhci_create_device+0x5c/0x580 [hci_vhci]
    [<ffffffffa0219436>] vhci_write+0x306/0x4c8 [hci_vhci]

Fixes: 23424c0d31 (Bluetooth: Add support creating virtual AMP controllers)
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
---
 drivers/bluetooth/hci_vhci.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/bluetooth/hci_vhci.c b/drivers/bluetooth/hci_vhci.c
index e1974a6..a269b34 100644
--- a/drivers/bluetooth/hci_vhci.c
+++ b/drivers/bluetooth/hci_vhci.c
@@ -352,6 +352,7 @@ static int vhci_release(struct inode *inode, struct file *file)
 		hci_free_dev(hdev);
 	}
 
+	skb_queue_purge(&data->readq);
 	file->private_data = NULL;
 	kfree(data);
 
-- 
2.7.4