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303911cfc5
The syzbot fuzzer has found two (!) races in the USB character device
registration and deregistration routines. This patch fixes the races.
The first race results from the fact that usb_deregister_dev() sets
usb_minors[intf->minor] to NULL before calling device_destroy() on the
class device. This leaves a window during which another thread can
allocate the same minor number but will encounter a duplicate name
error when it tries to register its own class device. A typical error
message in the system log would look like:
sysfs: cannot create duplicate filename '/class/usbmisc/ldusb0'
The patch fixes this race by destroying the class device first.
The second race is in usb_register_dev(). When that routine runs, it
first allocates a minor number, then drops minor_rwsem, and then
creates the class device. If the device creation fails, the minor
number is deallocated and the whole routine returns an error. But
during the time while minor_rwsem was dropped, there is a window in
which the minor number is allocated and so another thread can
successfully open the device file. Typically this results in
use-after-free errors or invalid accesses when the other thread closes
its open file reference, because the kernel then tries to release
resources that were already deallocated when usb_register_dev()
failed. The patch fixes this race by keeping minor_rwsem locked
throughout the entire routine.
Reported-and-tested-by: syzbot+30cf45ebfe0b0c4847a1@syzkaller.appspotmail.com
Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
CC: <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/Pine.LNX.4.44L0.1908121607590.1659-100000@iolanthe.rowland.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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| 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 | ||
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| COPYING | ||
| CREDITS | ||
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| 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.