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The syzbot fuzzer found a bug in the p54 USB wireless driver. The issue involves a race between disconnect and the firmware-loader callback routine, and it has several aspects. One big problem is that when the firmware can't be loaded, the callback routine tries to unbind the driver from the USB _device_ (by calling device_release_driver) instead of from the USB _interface_ to which it is actually bound (by calling usb_driver_release_interface). The race involves access to the private data structure. The driver's disconnect handler waits for a completion that is signalled by the firmware-loader callback routine. As soon as the completion is signalled, you have to assume that the private data structure may have been deallocated by the disconnect handler -- even if the firmware was loaded without errors. However, the callback routine does access the private data several times after that point. Another problem is that, in order to ensure that the USB device structure hasn't been freed when the callback routine runs, the driver takes a reference to it. This isn't good enough any more, because now that the callback routine calls usb_driver_release_interface, it has to ensure that the interface structure hasn't been freed. Finally, the driver takes an unnecessary reference to the USB device structure in the probe function and drops the reference in the disconnect handler. This extra reference doesn't accomplish anything, because the USB core already guarantees that a device structure won't be deallocated while a driver is still bound to any of its interfaces. To fix these problems, this patch makes the following changes: Call usb_driver_release_interface() rather than device_release_driver(). Don't signal the completion until after the important information has been copied out of the private data structure, and don't refer to the private data at all thereafter. Lock udev (the interface's parent) before unbinding the driver instead of locking udev->parent. During the firmware loading process, take a reference to the USB interface instead of the USB device. Don't take an unnecessary reference to the device during probe (and then don't drop it during disconnect). Signed-off-by: Alan Stern <stern@rowland.harvard.edu> Reported-and-tested-by: syzbot+200d4bb11b23d929335f@syzkaller.appspotmail.com CC: <stable@vger.kernel.org> Acked-by: Christian Lamparter <chunkeey@gmail.com> Signed-off-by: Kalle Valo <kvalo@codeaurora.org> |
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| Documentation | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| mm | ||
| net | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| README | ||
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.