linux-stable.git/drivers/base/bus.c, branch linux-4.9.y Linux kernel stable tree sysfs: Disable lockdep for driver bind/unbind files 2019-01-26T08:38:35+00:00 Daniel Vetter daniel.vetter@ffwll.ch 2018-12-19T12:39:09+00:00 54e6f64efc14213c2e76ea063645392a955b67e4 [ Upstream commit 4f4b374332ec0ae9c738ff8ec9bed5cd97ff9adc ] This is the much more correct fix for my earlier attempt at: https://lkml.org/lkml/2018/12/10/118 Short recap: - There's not actually a locking issue, it's just lockdep being a bit too eager to complain about a possible deadlock. - Contrary to what I claimed the real problem is recursion on kn->count. Greg pointed me at sysfs_break_active_protection(), used by the scsi subsystem to allow a sysfs file to unbind itself. That would be a real deadlock, which isn't what's happening here. Also, breaking the active protection means we'd need to manually handle all the lifetime fun. - With Rafael we discussed the task_work approach, which kinda works, but has two downsides: It's a functional change for a lockdep annotation issue, and it won't work for the bind file (which needs to get the errno from the driver load function back to userspace). - Greg also asked why this never showed up: To hit this you need to unregister a 2nd driver from the unload code of your first driver. I guess only gpus do that. The bug has always been there, but only with a recent patch series did we add more locks so that lockdep built a chain from unbinding the snd-hda driver to the acpi_video_unregister call. Full lockdep splat: [12301.898799] ============================================ [12301.898805] WARNING: possible recursive locking detected [12301.898811] 4.20.0-rc7+ #84 Not tainted [12301.898815] -------------------------------------------- [12301.898821] bash/5297 is trying to acquire lock: [12301.898826] 00000000f61c6093 (kn->count#39){++++}, at: kernfs_remove_by_name_ns+0x3b/0x80 [12301.898841] but task is already holding lock: [12301.898847] 000000005f634021 (kn->count#39){++++}, at: kernfs_fop_write+0xdc/0x190 [12301.898856] other info that might help us debug this: [12301.898862] Possible unsafe locking scenario: [12301.898867] CPU0 [12301.898870] ---- [12301.898874] lock(kn->count#39); [12301.898879] lock(kn->count#39); [12301.898883] *** DEADLOCK *** [12301.898891] May be due to missing lock nesting notation [12301.898899] 5 locks held by bash/5297: [12301.898903] #0: 00000000cd800e54 (sb_writers#4){.+.+}, at: vfs_write+0x17f/0x1b0 [12301.898915] #1: 000000000465e7c2 (&of->mutex){+.+.}, at: kernfs_fop_write+0xd3/0x190 [12301.898925] #2: 000000005f634021 (kn->count#39){++++}, at: kernfs_fop_write+0xdc/0x190 [12301.898936] #3: 00000000414ef7ac (&dev->mutex){....}, at: device_release_driver_internal+0x34/0x240 [12301.898950] #4: 000000003218fbdf (register_count_mutex){+.+.}, at: acpi_video_unregister+0xe/0x40 [12301.898960] stack backtrace: [12301.898968] CPU: 1 PID: 5297 Comm: bash Not tainted 4.20.0-rc7+ #84 [12301.898974] Hardware name: Hewlett-Packard HP EliteBook 8460p/161C, BIOS 68SCF Ver. F.01 03/11/2011 [12301.898982] Call Trace: [12301.898989] dump_stack+0x67/0x9b [12301.898997] __lock_acquire+0x6ad/0x1410 [12301.899003] ? kernfs_remove_by_name_ns+0x3b/0x80 [12301.899010] ? find_held_lock+0x2d/0x90 [12301.899017] ? mutex_spin_on_owner+0xe4/0x150 [12301.899023] ? find_held_lock+0x2d/0x90 [12301.899030] ? lock_acquire+0x90/0x180 [12301.899036] lock_acquire+0x90/0x180 [12301.899042] ? kernfs_remove_by_name_ns+0x3b/0x80 [12301.899049] __kernfs_remove+0x296/0x310 [12301.899055] ? kernfs_remove_by_name_ns+0x3b/0x80 [12301.899060] ? kernfs_name_hash+0xd/0x80 [12301.899066] ? kernfs_find_ns+0x6c/0x100 [12301.899073] kernfs_remove_by_name_ns+0x3b/0x80 [12301.899080] bus_remove_driver+0x92/0xa0 [12301.899085] acpi_video_unregister+0x24/0x40 [12301.899127] i915_driver_unload+0x42/0x130 [i915] [12301.899160] i915_pci_remove+0x19/0x30 [i915] [12301.899169] pci_device_remove+0x36/0xb0 [12301.899176] device_release_driver_internal+0x185/0x240 [12301.899183] unbind_store+0xaf/0x180 [12301.899189] kernfs_fop_write+0x104/0x190 [12301.899195] __vfs_write+0x31/0x180 [12301.899203] ? rcu_read_lock_sched_held+0x6f/0x80 [12301.899209] ? rcu_sync_lockdep_assert+0x29/0x50 [12301.899216] ? __sb_start_write+0x13c/0x1a0 [12301.899221] ? vfs_write+0x17f/0x1b0 [12301.899227] vfs_write+0xb9/0x1b0 [12301.899233] ksys_write+0x50/0xc0 [12301.899239] do_syscall_64+0x4b/0x180 [12301.899247] entry_SYSCALL_64_after_hwframe+0x49/0xbe [12301.899253] RIP: 0033:0x7f452ac7f7a4 [12301.899259] Code: 00 f7 d8 64 89 02 48 c7 c0 ff ff ff ff eb b7 0f 1f 80 00 00 00 00 8b 05 aa f0 2c 00 48 63 ff 85 c0 75 13 b8 01 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 54 f3 c3 66 90 55 53 48 89 d5 48 89 f3 48 83 [12301.899273] RSP: 002b:00007ffceafa6918 EFLAGS: 00000246 ORIG_RAX: 0000000000000001 [12301.899282] RAX: ffffffffffffffda RBX: 000000000000000d RCX: 00007f452ac7f7a4 [12301.899288] RDX: 000000000000000d RSI: 00005612a1abf7c0 RDI: 0000000000000001 [12301.899295] RBP: 00005612a1abf7c0 R08: 000000000000000a R09: 00005612a1c46730 [12301.899301] R10: 000000000000000a R11: 0000000000000246 R12: 000000000000000d [12301.899308] R13: 0000000000000001 R14: 00007f452af4a740 R15: 000000000000000d Looking around I've noticed that usb and i2c already handle similar recursion problems, where a sysfs file can unbind the same type of sysfs somewhere else in the hierarchy. Relevant commits are: commit 356c05d58af05d582e634b54b40050c73609617b Author: Alan Stern <stern@rowland.harvard.edu> Date: Mon May 14 13:30:03 2012 -0400 sysfs: get rid of some lockdep false positives commit e9b526fe704812364bca07edd15eadeba163ebfb Author: Alexander Sverdlin <alexander.sverdlin@nsn.com> Date: Fri May 17 14:56:35 2013 +0200 i2c: suppress lockdep warning on delete_device Implement the same trick for driver bind/unbind. v2: Put the macro into bus.c (Greg). Reviewed-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> Cc: Ramalingam C <ramalingam.c@intel.com> Cc: Arend van Spriel <aspriel@gmail.com> Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com> Cc: Geert Uytterhoeven <geert+renesas@glider.be> Cc: Bartosz Golaszewski <brgl@bgdev.pl> Cc: Heikki Krogerus <heikki.krogerus@linux.intel.com> Cc: Vivek Gautam <vivek.gautam@codeaurora.org> Cc: Joe Perches <joe@perches.com> Signed-off-by: Daniel Vetter <daniel.vetter@intel.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Sasha Levin <sashal@kernel.org> 
[ Upstream commit 4f4b374332ec0ae9c738ff8ec9bed5cd97ff9adc ]

This is the much more correct fix for my earlier attempt at:

https://lkml.org/lkml/2018/12/10/118

Short recap:

- There's not actually a locking issue, it's just lockdep being a bit
  too eager to complain about a possible deadlock.

- Contrary to what I claimed the real problem is recursion on
  kn->count. Greg pointed me at sysfs_break_active_protection(), used
  by the scsi subsystem to allow a sysfs file to unbind itself. That
  would be a real deadlock, which isn't what's happening here. Also,
  breaking the active protection means we'd need to manually handle
  all the lifetime fun.

- With Rafael we discussed the task_work approach, which kinda works,
  but has two downsides: It's a functional change for a lockdep
  annotation issue, and it won't work for the bind file (which needs
  to get the errno from the driver load function back to userspace).

- Greg also asked why this never showed up: To hit this you need to
  unregister a 2nd driver from the unload code of your first driver. I
  guess only gpus do that. The bug has always been there, but only
  with a recent patch series did we add more locks so that lockdep
  built a chain from unbinding the snd-hda driver to the
  acpi_video_unregister call.

Full lockdep splat:

[12301.898799] ============================================
[12301.898805] WARNING: possible recursive locking detected
[12301.898811] 4.20.0-rc7+ #84 Not tainted
[12301.898815] --------------------------------------------
[12301.898821] bash/5297 is trying to acquire lock:
[12301.898826] 00000000f61c6093 (kn->count#39){++++}, at: kernfs_remove_by_name_ns+0x3b/0x80
[12301.898841] but task is already holding lock:
[12301.898847] 000000005f634021 (kn->count#39){++++}, at: kernfs_fop_write+0xdc/0x190
[12301.898856] other info that might help us debug this:
[12301.898862]  Possible unsafe locking scenario:
[12301.898867]        CPU0
[12301.898870]        ----
[12301.898874]   lock(kn->count#39);
[12301.898879]   lock(kn->count#39);
[12301.898883] *** DEADLOCK ***
[12301.898891]  May be due to missing lock nesting notation
[12301.898899] 5 locks held by bash/5297:
[12301.898903]  #0: 00000000cd800e54 (sb_writers#4){.+.+}, at: vfs_write+0x17f/0x1b0
[12301.898915]  #1: 000000000465e7c2 (&of->mutex){+.+.}, at: kernfs_fop_write+0xd3/0x190
[12301.898925]  #2: 000000005f634021 (kn->count#39){++++}, at: kernfs_fop_write+0xdc/0x190
[12301.898936]  #3: 00000000414ef7ac (&dev->mutex){....}, at: device_release_driver_internal+0x34/0x240
[12301.898950]  #4: 000000003218fbdf (register_count_mutex){+.+.}, at: acpi_video_unregister+0xe/0x40
[12301.898960] stack backtrace:
[12301.898968] CPU: 1 PID: 5297 Comm: bash Not tainted 4.20.0-rc7+ #84
[12301.898974] Hardware name: Hewlett-Packard HP EliteBook 8460p/161C, BIOS 68SCF Ver. F.01 03/11/2011
[12301.898982] Call Trace:
[12301.898989]  dump_stack+0x67/0x9b
[12301.898997]  __lock_acquire+0x6ad/0x1410
[12301.899003]  ? kernfs_remove_by_name_ns+0x3b/0x80
[12301.899010]  ? find_held_lock+0x2d/0x90
[12301.899017]  ? mutex_spin_on_owner+0xe4/0x150
[12301.899023]  ? find_held_lock+0x2d/0x90
[12301.899030]  ? lock_acquire+0x90/0x180
[12301.899036]  lock_acquire+0x90/0x180
[12301.899042]  ? kernfs_remove_by_name_ns+0x3b/0x80
[12301.899049]  __kernfs_remove+0x296/0x310
[12301.899055]  ? kernfs_remove_by_name_ns+0x3b/0x80
[12301.899060]  ? kernfs_name_hash+0xd/0x80
[12301.899066]  ? kernfs_find_ns+0x6c/0x100
[12301.899073]  kernfs_remove_by_name_ns+0x3b/0x80
[12301.899080]  bus_remove_driver+0x92/0xa0
[12301.899085]  acpi_video_unregister+0x24/0x40
[12301.899127]  i915_driver_unload+0x42/0x130 [i915]
[12301.899160]  i915_pci_remove+0x19/0x30 [i915]
[12301.899169]  pci_device_remove+0x36/0xb0
[12301.899176]  device_release_driver_internal+0x185/0x240
[12301.899183]  unbind_store+0xaf/0x180
[12301.899189]  kernfs_fop_write+0x104/0x190
[12301.899195]  __vfs_write+0x31/0x180
[12301.899203]  ? rcu_read_lock_sched_held+0x6f/0x80
[12301.899209]  ? rcu_sync_lockdep_assert+0x29/0x50
[12301.899216]  ? __sb_start_write+0x13c/0x1a0
[12301.899221]  ? vfs_write+0x17f/0x1b0
[12301.899227]  vfs_write+0xb9/0x1b0
[12301.899233]  ksys_write+0x50/0xc0
[12301.899239]  do_syscall_64+0x4b/0x180
[12301.899247]  entry_SYSCALL_64_after_hwframe+0x49/0xbe
[12301.899253] RIP: 0033:0x7f452ac7f7a4
[12301.899259] Code: 00 f7 d8 64 89 02 48 c7 c0 ff ff ff ff eb b7 0f 1f 80 00 00 00 00 8b 05 aa f0 2c 00 48 63 ff 85 c0 75 13 b8 01 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 54 f3 c3 66 90 55 53 48 89 d5 48 89 f3 48 83
[12301.899273] RSP: 002b:00007ffceafa6918 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
[12301.899282] RAX: ffffffffffffffda RBX: 000000000000000d RCX: 00007f452ac7f7a4
[12301.899288] RDX: 000000000000000d RSI: 00005612a1abf7c0 RDI: 0000000000000001
[12301.899295] RBP: 00005612a1abf7c0 R08: 000000000000000a R09: 00005612a1c46730
[12301.899301] R10: 000000000000000a R11: 0000000000000246 R12: 000000000000000d
[12301.899308] R13: 0000000000000001 R14: 00007f452af4a740 R15: 000000000000000d

Looking around I've noticed that usb and i2c already handle similar
recursion problems, where a sysfs file can unbind the same type of
sysfs somewhere else in the hierarchy. Relevant commits are:

commit 356c05d58af05d582e634b54b40050c73609617b
Author: Alan Stern <stern@rowland.harvard.edu>
Date:   Mon May 14 13:30:03 2012 -0400

    sysfs: get rid of some lockdep false positives

commit e9b526fe704812364bca07edd15eadeba163ebfb
Author: Alexander Sverdlin <alexander.sverdlin@nsn.com>
Date:   Fri May 17 14:56:35 2013 +0200

    i2c: suppress lockdep warning on delete_device

Implement the same trick for driver bind/unbind.

v2: Put the macro into bus.c (Greg).

Reviewed-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Cc: Ramalingam C <ramalingam.c@intel.com>
Cc: Arend van Spriel <aspriel@gmail.com>
Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Geert Uytterhoeven <geert+renesas@glider.be>
Cc: Bartosz Golaszewski <brgl@bgdev.pl>
Cc: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Cc: Vivek Gautam <vivek.gautam@codeaurora.org>
Cc: Joe Perches <joe@perches.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
driver core: bus: Fix a potential double free 2017-09-09T15:39:38+00:00 Christophe JAILLET christophe.jaillet@wanadoo.fr 2017-08-29T19:23:49+00:00 5555eb956edc3c89f59ed7636b29a3a4d0dd8063 commit 0f9b011d3321ca1079c7a46c18cb1956fbdb7bcb upstream. The .release function of driver_ktype is 'driver_release()'. This function frees the container_of this kobject. So, this memory must not be freed explicitly in the error handling path of 'bus_add_driver()'. Otherwise a double free will occur. Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
commit 0f9b011d3321ca1079c7a46c18cb1956fbdb7bcb upstream.

The .release function of driver_ktype is 'driver_release()'.
This function frees the container_of this kobject.

So, this memory must not be freed explicitly in the error handling path of
'bus_add_driver()'. Otherwise a double free will occur.

Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
driver core: bus: use to_subsys_private and to_device_private_bus 2016-02-10T01:25:27+00:00 Geliang Tang geliangtang@163.com 2016-01-05T15:03:38+00:00 371fd7a2c438a56e00c18a83178555a7918329a2 Use to_subsys_private() and to_device_private_bus() instead of open-coding. Signed-off-by: Geliang Tang <geliangtang@163.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
Use to_subsys_private() and to_device_private_bus() instead of open-coding.

Signed-off-by: Geliang Tang <geliangtang@163.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
driver core: bus: use list_for_each_entry* 2016-02-10T01:25:27+00:00 Geliang Tang geliangtang@163.com 2016-01-05T15:03:37+00:00 4c62785e670e978294222a42200346f0538e19e7 Use list_for_each_entry*() instead of list_for_each*() to simplify the code. Signed-off-by: Geliang Tang <geliangtang@163.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
Use list_for_each_entry*() instead of list_for_each*() to simplify
the code.

Signed-off-by: Geliang Tang <geliangtang@163.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
driver-core: add asynchronous probing support for drivers 2015-05-20T07:25:24+00:00 Dmitry Torokhov dmitry.torokhov@gmail.com 2015-03-30T23:20:04+00:00 765230b5f084863183aa8adb3405ab3f32c0b16e Some devices take a long time when initializing, and not all drivers are suited to initialize their devices when they are open. For example, input drivers need to interrogate their devices in order to publish device's capabilities before userspace will open them. When such drivers are compiled into kernel they may stall entire kernel initialization. This change allows drivers request for their probe functions to be called asynchronously during driver and device registration (manual binding is still synchronous). Because async_schedule is used to perform asynchronous calls module loading will still wait for the probing to complete. Note that the end goal is to make the probing asynchronous by default, so annotating drivers with PROBE_PREFER_ASYNCHRONOUS is a temporary measure that allows us to speed up boot process while we validating and fixing the rest of the drivers and preparing userspace. This change is based on earlier patch by "Luis R. Rodriguez" <mcgrof@suse.com> Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
Some devices take a long time when initializing, and not all drivers are
suited to initialize their devices when they are open. For example,
input drivers need to interrogate their devices in order to publish
device's capabilities before userspace will open them. When such drivers
are compiled into kernel they may stall entire kernel initialization.

This change allows drivers request for their probe functions to be
called asynchronously during driver and device registration (manual
binding is still synchronous). Because async_schedule is used to perform
asynchronous calls module loading will still wait for the probing to
complete.

Note that the end goal is to make the probing asynchronous by default,
so annotating drivers with PROBE_PREFER_ASYNCHRONOUS is a temporary
measure that allows us to speed up boot process while we validating and
fixing the rest of the drivers and preparing userspace.

This change is based on earlier patch by "Luis R. Rodriguez"
<mcgrof@suse.com>

Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
driver core: bus: Goto appropriate labels on failure in bus_add_device 2015-03-25T12:40:31+00:00 Junjie Mao junjie_mao@yeah.net 2015-01-28T02:02:44+00:00 1c34203a1496d1849ba978021b878b3447d433c8 It is not necessary to call device_remove_groups() when device_add_groups() fails. The group added by device_add_groups() should be removed if sysfs_create_link() fails. Fixes: fa6fdb33b486 ("driver core: bus_type: add dev_groups") Signed-off-by: Junjie Mao <junjie_mao@yeah.net> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
It is not necessary to call device_remove_groups() when device_add_groups()
fails.

The group added by device_add_groups() should be removed if sysfs_create_link()
fails.

Fixes: fa6fdb33b486 ("driver core: bus_type: add dev_groups")
Signed-off-by: Junjie Mao <junjie_mao@yeah.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
driver core: Fix unbalanced device reference in drivers_probe 2014-11-07T19:17:27+00:00 Alex Williamson alex.williamson@redhat.com 2014-10-31T17:13:07+00:00 0372ffb35d00288802265586a29c117911d02fb8 bus_find_device_by_name() acquires a device reference which is never released. This results in an object leak, which on older kernels results in failure to release all resources of PCI devices. libvirt uses drivers_probe to re-attach devices to the host after assignment and is therefore a common trigger for this leak. Example: # cd /sys/bus/pci/ # dmesg -C # echo 1 > devices/0000\:01\:00.0/sriov_numvfs # echo 0 > devices/0000\:01\:00.0/sriov_numvfs # dmesg | grep 01:10 pci 0000:01:10.0: [8086:10ca] type 00 class 0x020000 kobject: '0000:01:10.0' (ffff8801d79cd0a8): kobject_add_internal: parent: '0000:00:01.0', set: 'devices' kobject: '0000:01:10.0' (ffff8801d79cd0a8): kobject_uevent_env kobject: '0000:01:10.0' (ffff8801d79cd0a8): fill_kobj_path: path = '/devices/pci0000:00/0000:00:01.0/0000:01:10.0' kobject: '0000:01:10.0' (ffff8801d79cd0a8): kobject_uevent_env kobject: '0000:01:10.0' (ffff8801d79cd0a8): fill_kobj_path: path = '/devices/pci0000:00/0000:00:01.0/0000:01:10.0' kobject: '0000:01:10.0' (ffff8801d79cd0a8): kobject_uevent_env kobject: '0000:01:10.0' (ffff8801d79cd0a8): fill_kobj_path: path = '/devices/pci0000:00/0000:00:01.0/0000:01:10.0' kobject: '0000:01:10.0' (ffff8801d79cd0a8): kobject_cleanup, parent (null) kobject: '0000:01:10.0' (ffff8801d79cd0a8): calling ktype release kobject: '0000:01:10.0': free name [kobject freed as expected] # dmesg -C # echo 1 > devices/0000\:01\:00.0/sriov_numvfs # echo 0000:01:10.0 > drivers_probe # echo 0 > devices/0000\:01\:00.0/sriov_numvfs # dmesg | grep 01:10 pci 0000:01:10.0: [8086:10ca] type 00 class 0x020000 kobject: '0000:01:10.0' (ffff8801d79ce0a8): kobject_add_internal: parent: '0000:00:01.0', set: 'devices' kobject: '0000:01:10.0' (ffff8801d79ce0a8): kobject_uevent_env kobject: '0000:01:10.0' (ffff8801d79ce0a8): fill_kobj_path: path = '/devices/pci0000:00/0000:00:01.0/0000:01:10.0' kobject: '0000:01:10.0' (ffff8801d79ce0a8): kobject_uevent_env kobject: '0000:01:10.0' (ffff8801d79ce0a8): fill_kobj_path: path = '/devices/pci0000:00/0000:00:01.0/0000:01:10.0' kobject: '0000:01:10.0' (ffff8801d79ce0a8): kobject_uevent_env kobject: '0000:01:10.0' (ffff8801d79ce0a8): fill_kobj_path: path = '/devices/pci0000:00/0000:00:01.0/0000:01:10.0' [no free] Signed-off-by: Alex Williamson <alex.williamson@redhat.com> Cc: stable@vger.kernel.org Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
bus_find_device_by_name() acquires a device reference which is never
released.  This results in an object leak, which on older kernels
results in failure to release all resources of PCI devices.  libvirt
uses drivers_probe to re-attach devices to the host after assignment
and is therefore a common trigger for this leak.

Example:

# cd /sys/bus/pci/
# dmesg -C
# echo 1 > devices/0000\:01\:00.0/sriov_numvfs
# echo 0 > devices/0000\:01\:00.0/sriov_numvfs
# dmesg | grep 01:10
 pci 0000:01:10.0: [8086:10ca] type 00 class 0x020000
 kobject: '0000:01:10.0' (ffff8801d79cd0a8): kobject_add_internal: parent: '0000:00:01.0', set: 'devices'
 kobject: '0000:01:10.0' (ffff8801d79cd0a8): kobject_uevent_env
 kobject: '0000:01:10.0' (ffff8801d79cd0a8): fill_kobj_path: path = '/devices/pci0000:00/0000:00:01.0/0000:01:10.0'
 kobject: '0000:01:10.0' (ffff8801d79cd0a8): kobject_uevent_env
 kobject: '0000:01:10.0' (ffff8801d79cd0a8): fill_kobj_path: path = '/devices/pci0000:00/0000:00:01.0/0000:01:10.0'
 kobject: '0000:01:10.0' (ffff8801d79cd0a8): kobject_uevent_env
 kobject: '0000:01:10.0' (ffff8801d79cd0a8): fill_kobj_path: path = '/devices/pci0000:00/0000:00:01.0/0000:01:10.0'
 kobject: '0000:01:10.0' (ffff8801d79cd0a8): kobject_cleanup, parent           (null)
 kobject: '0000:01:10.0' (ffff8801d79cd0a8): calling ktype release
 kobject: '0000:01:10.0': free name

[kobject freed as expected]

# dmesg -C
# echo 1 > devices/0000\:01\:00.0/sriov_numvfs
# echo 0000:01:10.0 > drivers_probe
# echo 0 > devices/0000\:01\:00.0/sriov_numvfs
# dmesg | grep 01:10
 pci 0000:01:10.0: [8086:10ca] type 00 class 0x020000
 kobject: '0000:01:10.0' (ffff8801d79ce0a8): kobject_add_internal: parent: '0000:00:01.0', set: 'devices'
 kobject: '0000:01:10.0' (ffff8801d79ce0a8): kobject_uevent_env
 kobject: '0000:01:10.0' (ffff8801d79ce0a8): fill_kobj_path: path = '/devices/pci0000:00/0000:00:01.0/0000:01:10.0'
 kobject: '0000:01:10.0' (ffff8801d79ce0a8): kobject_uevent_env
 kobject: '0000:01:10.0' (ffff8801d79ce0a8): fill_kobj_path: path = '/devices/pci0000:00/0000:00:01.0/0000:01:10.0'
 kobject: '0000:01:10.0' (ffff8801d79ce0a8): kobject_uevent_env
 kobject: '0000:01:10.0' (ffff8801d79ce0a8): fill_kobj_path: path = '/devices/pci0000:00/0000:00:01.0/0000:01:10.0'

[no free]

Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Cc: stable@vger.kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Merge branch 'master' into for-next 2014-02-20T13:54:28+00:00 Jiri Kosina jkosina@suse.cz 2014-02-20T13:54:28+00:00 d4263348f796f29546f90802177865dd4379dd0a 






treewide: Fix typo in Documentation/DocBook
2014-02-19T13:58:17+00:00

Masanari Iida
standby24x7@gmail.com

2014-02-18T13:54:36+00:00

e227867f12302633737bd2a48a10a9a72c0630cb

This patch fix spelling typo in Documentation/DocBook.
It is because .html and .xml files are generated by make htmldocs,
I have to fix a typo within the source files.

Signed-off-by: Masanari Iida <standby24x7@gmail.com>
Acked-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>





This patch fix spelling typo in Documentation/DocBook.
It is because .html and .xml files are generated by make htmldocs,
I have to fix a typo within the source files.

Signed-off-by: Masanari Iida <standby24x7@gmail.com>
Acked-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>







driver-core: Fix use-after-free triggered by bus_unregister()
2014-01-08T23:36:18+00:00

Bart Van Assche
bvanassche@acm.org

2014-01-04T13:21:42+00:00

174be70b638ceb1038f466b5ca014f6b1d9c8a59

Avoid that bus_unregister() triggers a use-after-free with
CONFIG_DEBUG_KOBJECT_RELEASE=y. This patch avoids that the
following sequence triggers a kernel crash with memory poisoning
enabled:
* bus_register()
* driver_register()
* driver_unregister()
* bus_unregister()

The above sequence causes the bus private data to be freed from
inside the bus_unregister() call although it is not guaranteed in
that function that the reference count on the bus private data has
dropped to zero. As an example, with CONFIG_DEBUG_KOBJECT_RELEASE=y
the ${bus}/drivers kobject is still holding a reference on
bus->p->subsys.kobj via its parent pointer at the time the bus
private data is freed. Fix this by deferring freeing the bus private
data until the last kobject_put() call on bus->p->subsys.kobj.

The kernel oops triggered by the above sequence and with memory
poisoning enabled and that is fixed by this patch is as follows:

general protection fault: 0000 [#1] PREEMPT SMP
CPU: 3 PID: 2711 Comm: kworker/3:32 Tainted: G        W  O 3.13.0-rc4-debug+ #1
Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
Workqueue: events kobject_delayed_cleanup
task: ffff880037f866d0 ti: ffff88003b638000 task.ti: ffff88003b638000
Call Trace:
 [<ffffffff81263105>] ? kobject_get_path+0x25/0x100
 [<ffffffff81264354>] kobject_uevent_env+0x134/0x600
 [<ffffffff8126482b>] kobject_uevent+0xb/0x10
 [<ffffffff81262fa2>] kobject_delayed_cleanup+0xc2/0x1b0
 [<ffffffff8106c047>] process_one_work+0x217/0x700
 [<ffffffff8106bfdb>] ? process_one_work+0x1ab/0x700
 [<ffffffff8106c64b>] worker_thread+0x11b/0x3a0
 [<ffffffff8106c530>] ? process_one_work+0x700/0x700
 [<ffffffff81074b70>] kthread+0xf0/0x110
 [<ffffffff81074a80>] ? insert_kthread_work+0x80/0x80
 [<ffffffff815673bc>] ret_from_fork+0x7c/0xb0
 [<ffffffff81074a80>] ? insert_kthread_work+0x80/0x80
Code: 89 f8 48 89 e5 f6 82 c0 27 63 81 20 74 15 0f 1f 44 00 00 48 83 c0 01 0f b6 10 f6 82 c0 27 63 81 20 75 f0 5d c3 66 0f 1f 44 00 00 <80> 3f 00 55 48 89 e5 74 15 48 89 f8 0f 1f 40 00 48 83 c0 01 80
RIP  [<ffffffff81267ed0>] strlen+0x0/0x30
 RSP <ffff88003b639c70>
---[ end trace 210f883ef80376aa ]---

Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Acked-by: Ming Lei <ming.lei@canonical.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>





Avoid that bus_unregister() triggers a use-after-free with
CONFIG_DEBUG_KOBJECT_RELEASE=y. This patch avoids that the
following sequence triggers a kernel crash with memory poisoning
enabled:
* bus_register()
* driver_register()
* driver_unregister()
* bus_unregister()

The above sequence causes the bus private data to be freed from
inside the bus_unregister() call although it is not guaranteed in
that function that the reference count on the bus private data has
dropped to zero. As an example, with CONFIG_DEBUG_KOBJECT_RELEASE=y
the ${bus}/drivers kobject is still holding a reference on
bus->p->subsys.kobj via its parent pointer at the time the bus
private data is freed. Fix this by deferring freeing the bus private
data until the last kobject_put() call on bus->p->subsys.kobj.

The kernel oops triggered by the above sequence and with memory
poisoning enabled and that is fixed by this patch is as follows:

general protection fault: 0000 [#1] PREEMPT SMP
CPU: 3 PID: 2711 Comm: kworker/3:32 Tainted: G        W  O 3.13.0-rc4-debug+ #1
Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
Workqueue: events kobject_delayed_cleanup
task: ffff880037f866d0 ti: ffff88003b638000 task.ti: ffff88003b638000
Call Trace:
 [<ffffffff81263105>] ? kobject_get_path+0x25/0x100
 [<ffffffff81264354>] kobject_uevent_env+0x134/0x600
 [<ffffffff8126482b>] kobject_uevent+0xb/0x10
 [<ffffffff81262fa2>] kobject_delayed_cleanup+0xc2/0x1b0
 [<ffffffff8106c047>] process_one_work+0x217/0x700
 [<ffffffff8106bfdb>] ? process_one_work+0x1ab/0x700
 [<ffffffff8106c64b>] worker_thread+0x11b/0x3a0
 [<ffffffff8106c530>] ? process_one_work+0x700/0x700
 [<ffffffff81074b70>] kthread+0xf0/0x110
 [<ffffffff81074a80>] ? insert_kthread_work+0x80/0x80
 [<ffffffff815673bc>] ret_from_fork+0x7c/0xb0
 [<ffffffff81074a80>] ? insert_kthread_work+0x80/0x80
Code: 89 f8 48 89 e5 f6 82 c0 27 63 81 20 74 15 0f 1f 44 00 00 48 83 c0 01 0f b6 10 f6 82 c0 27 63 81 20 75 f0 5d c3 66 0f 1f 44 00 00 <80> 3f 00 55 48 89 e5 74 15 48 89 f8 0f 1f 40 00 48 83 c0 01 80
RIP  [<ffffffff81267ed0>] strlen+0x0/0x30
 RSP <ffff88003b639c70>
---[ end trace 210f883ef80376aa ]---

Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Acked-by: Ming Lei <ming.lei@canonical.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>