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Shigeru Yoshida 85c3d26bd7 ohci-hcd: Fix race condition caused by ohci_urb_enqueue() and io_watchdog_func() 
commit b2685bdacd upstream.

Running io_watchdog_func() while ohci_urb_enqueue() is running can
cause a race condition where ohci->prev_frame_no is corrupted and the
watchdog can mis-detect following error:

  ohci-platform 664a0800.usb: frame counter not updating; disabled
  ohci-platform 664a0800.usb: HC died; cleaning up

Specifically, following scenario causes a race condition:

  1. ohci_urb_enqueue() calls spin_lock_irqsave(&ohci->lock, flags)
     and enters the critical section
  2. ohci_urb_enqueue() calls timer_pending(&ohci->io_watchdog) and it
     returns false
  3. ohci_urb_enqueue() sets ohci->prev_frame_no to a frame number
     read by ohci_frame_no(ohci)
  4. ohci_urb_enqueue() schedules io_watchdog_func() with mod_timer()
  5. ohci_urb_enqueue() calls spin_unlock_irqrestore(&ohci->lock,
     flags) and exits the critical section
  6. Later, ohci_urb_enqueue() is called
  7. ohci_urb_enqueue() calls spin_lock_irqsave(&ohci->lock, flags)
     and enters the critical section
  8. The timer scheduled on step 4 expires and io_watchdog_func() runs
  9. io_watchdog_func() calls spin_lock_irqsave(&ohci->lock, flags)
     and waits on it because ohci_urb_enqueue() is already in the
     critical section on step 7
 10. ohci_urb_enqueue() calls timer_pending(&ohci->io_watchdog) and it
     returns false
 11. ohci_urb_enqueue() sets ohci->prev_frame_no to new frame number
     read by ohci_frame_no(ohci) because the frame number proceeded
     between step 3 and 6
 12. ohci_urb_enqueue() schedules io_watchdog_func() with mod_timer()
 13. ohci_urb_enqueue() calls spin_unlock_irqrestore(&ohci->lock,
     flags) and exits the critical section, then wake up
     io_watchdog_func() which is waiting on step 9
 14. io_watchdog_func() enters the critical section
 15. io_watchdog_func() calls ohci_frame_no(ohci) and set frame_no
     variable to the frame number
 16. io_watchdog_func() compares frame_no and ohci->prev_frame_no

On step 16, because this calling of io_watchdog_func() is scheduled on
step 4, the frame number set in ohci->prev_frame_no is expected to the
number set on step 3.  However, ohci->prev_frame_no is overwritten on
step 11.  Because step 16 is executed soon after step 11, the frame
number might not proceed, so ohci->prev_frame_no must equals to
frame_no.

To address above scenario, this patch introduces a special sentinel
value IO_WATCHDOG_OFF and set this value to ohci->prev_frame_no when
the watchdog is not pending or running.  When ohci_urb_enqueue()
schedules the watchdog (step 4 and 12 above), it compares
ohci->prev_frame_no to IO_WATCHDOG_OFF so that ohci->prev_frame_no is
not overwritten while io_watchdog_func() is running.

Signed-off-by: Shigeru Yoshida <Shigeru.Yoshida@windriver.com>
Signed-off-by: Haiqing Bai <Haiqing.Bai@windriver.com>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
History 2018-02-28 10:19:41 +01:00
arch x86/oprofile: Fix bogus GCC-8 warning in nmi_setup() 2018-02-28 10:19:41 +01:00
block blk_rq_map_user_iov: fix error override 2018-02-25 11:07:49 +01:00
certs License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
crypto PKCS#7: fix certificate blacklisting 2018-02-28 10:19:39 +01:00
Documentation ext4: correct documentation for grpid mount option 2018-02-22 15:42:26 +01:00
drivers ohci-hcd: Fix race condition caused by ohci_urb_enqueue() and io_watchdog_func() 2018-02-28 10:19:41 +01:00
firmware License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
fs btrfs: Fix possible off-by-one in btrfs_search_path_in_tree 2018-02-25 11:08:00 +01:00
include Kbuild: always define endianess in kconfig.h 2018-02-28 10:19:41 +01:00
init kmemcheck: stop using GFP_NOTRACK and SLAB_NOTRACK 2018-02-22 15:42:23 +01:00
ipc License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
kernel locking/lockdep: Fix possible NULL deref 2018-02-25 11:08:00 +01:00
lib 509: fix printing uninitialized stack memory when OID is empty 2018-02-25 11:08:01 +01:00
mm mm, swap, frontswap: fix THP swap if frontswap enabled 2018-02-28 10:19:41 +01:00
net cfg80211: fix cfg80211_beacon_dup 2018-02-28 10:19:39 +01:00
samples samples/bpf: adjust rlimit RLIMIT_MEMLOCK for xdp1 2017-12-20 10:10:31 +01:00
scripts scripts/kernel-doc: Don't fail with status != 0 if error encountered with -none 2018-02-25 11:07:58 +01:00
security selinux: skip bounded transition processing if the policy isn't loaded 2018-02-25 11:07:49 +01:00
sound ASoC: rsnd: ssi: fix race condition in rsnd_ssi_pointer_update 2018-02-25 11:08:02 +01:00
tools perf test: Fix test 21 for s390x 2018-02-25 11:07:55 +01:00
usr initramfs: fix initramfs rebuilds w/ compression after disabling 2017-11-03 07:39:19 -07:00
virt KVM: arm/arm64: Fix spinlock acquisition in vgic_set_owner 2018-02-25 11:07:56 +01:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore Add hch to .get_maintainer.ignore 2015-08-21 14:30:10 -07:00
.gitattributes .gitattributes: set git diff driver for C source code files 2016-10-07 18:46:30 -07:00
.gitignore kbuild: rpm-pkg: keep spec file until make mrproper 2018-02-13 10:19:46 +01:00
.mailmap .mailmap: Add Maciej W. Rozycki's Imagination e-mail address 2017-11-10 12:16:15 -08:00
COPYING [PATCH] update FSF address in COPYING 2005-09-10 10:06:29 -07:00
CREDITS MAINTAINERS: update TPM driver infrastructure changes 2017-11-09 17:58:40 -08:00
Kbuild License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
Kconfig License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
MAINTAINERS kmemcheck: rip it out 2018-02-22 15:42:24 +01:00
Makefile Linux 4.14.22 2018-02-25 11:08:04 +01:00
README README: add a new README file, pointing to the Documentation/ 2016-10-24 08:12:35 -02:00

README 

Linux kernel
============

This file was moved to Documentation/admin-guide/README.rst

Please notice that there are several guides for kernel developers and users.
These guides can be rendered in a number of formats, like HTML and PDF.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
See Documentation/00-INDEX for a list of what is contained in each file.

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.