commit 303911cfc5b95d33687d9046133ff184cf5043ff upstream.

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>

commit 2f86a96be0ccb1302b7eee7855dbee5ce4dc5dfb upstream.

There is race condition when two USB class drivers try to call
init_usb_class at the same time and leads to crash.
code path: probe->usb_register_dev->init_usb_class

To solve this, mutex locking has been added in init_usb_class() and
destroy_usb_class().

As pointed by Alan, removed "if (usb_class)" test from destroy_usb_class()
because usb_class can never be NULL there.

Signed-off-by: Ajay Kaher <ajay.kaher@samsung.com>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

kbasename() helper is dedicated to find a last part of the filename or
pathname. USB core uses open-coded variant of that helper.

Replace some lines of code by kbasename() call.

The current users do not have trailing slash and we are on the safe side to
make such change. I dig a history of the code under question up and found the
patch [1] that brought it along with the same to tty layer. The check for
trailing slash looks like copy'n'paste thing and I consider it as redundant.

[1] http://www.kernel.org/pub/linux/kernel//people/akpm/patches/2.5/2.5.69/2.5.69-mm3/broken-out/linus.patch

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Pull vfs updates from Al Viro:
 "All kinds of stuff this time around; some more notable parts:

   - RCU'd vfsmounts handling
   - new primitives for coredump handling
   - files_lock is gone
   - Bruce's delegations handling series
   - exportfs fixes

  plus misc stuff all over the place"

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: (101 commits)
  ecryptfs: ->f_op is never NULL
  locks: break delegations on any attribute modification
  locks: break delegations on link
  locks: break delegations on rename
  locks: helper functions for delegation breaking
  locks: break delegations on unlink
  namei: minor vfs_unlink cleanup
  locks: implement delegations
  locks: introduce new FL_DELEG lock flag
  vfs: take i_mutex on renamed file
  vfs: rename I_MUTEX_QUOTA now that it's not used for quotas
  vfs: don't use PARENT/CHILD lock classes for non-directories
  vfs: pull ext4's double-i_mutex-locking into common code
  exportfs: fix quadratic behavior in filehandle lookup
  exportfs: better variable name
  exportfs: move most of reconnect_path to helper function
  exportfs: eliminate unused "noprogress" counter
  exportfs: stop retrying once we race with rename/remove
  exportfs: clear DISCONNECTED on all parents sooner
  exportfs: more detailed comment for path_reconnect
  ...

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

Signed-off-by: Matthias Beyer <mail@beyermatthias.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

including:

- removing of trailing whitespace
- removing spaces before array indexing (foo [] to foo[])
- reindention of a switch-case block
- spaces to tabs

Signed-off-by: Matthias Beyer <mail@beyermatthias.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

When building the htmldocs (in verbose mode), scripts/kernel-doc reports the
following type of warnings:

Warning(drivers/usb/core/usb.c:76): No description found for return value of
'usb_find_alt_setting'

Fix them by:
- adding some missing descriptions of return values
- using "Return" sections for those descriptions

Signed-off-by: Yacine Belkadi <yacine.belkadi.1@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

There is a misprint in init_usb_class():
IS_ERR is used to get error code instead of PTR_ERR.

Found by Linux Driver Verification project (linuxtesting.org).

Signed-off-by: Alexey Khoroshilov <khoroshilov@ispras.ru>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

This class was not named properly years ago, and it turns out that tools
like udev can't properly see the devices in this class after booting due
to the fact that there is a bus with the same name in the system.

Changing this to "usbmisc" fixes this problem, and it solves the problem
for the future when we want to unify classes and busses.

Reported-by: Kay Sievers <kay@vrfy.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>