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HID: hiddev: Fix race in in hiddev_disconnect()

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commit 5c02c447eaeda29d3da121a2e17b97ccaf579b51 upstream.

Syzbot reports that "hiddev" is used after it's free in hiddev_disconnect().
The hiddev_disconnect() function sets "hiddev->exist = 0;" so
hiddev_release() can free it as soon as we drop the "existancelock"
lock.  This patch moves the mutex_unlock(&hiddev->existancelock) until
after we have finished using it.

Reported-by: syzbot+784ccb935f9900cc7c9e@syzkaller.appspotmail.com
Fixes: 7f77897ef2 ("HID: hiddev: fix potential use-after-free")
Suggested-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
dan.carpenter@oracle.com 2020-01-15 20:46:28 +03:00 • committed by Greg Kroah-Hartman
commit d5684b0515
1 changed files with 1 additions and 1 deletions
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2
drivers/hid/usbhid/hiddev.c
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@ -941,9 +941,9 @@ void hiddev_disconnect(struct hid_device *hid)
hiddev->exist = 0;
if (hiddev->open) {
mutex_unlock(&hiddev->existancelock);
hid_hw_close(hiddev->hid);
wake_up_interruptible(&hiddev->wait);
mutex_unlock(&hiddev->existancelock);
} else {
mutex_unlock(&hiddev->existancelock);
kfree(hiddev);