commit 15fffc6a5624b13b428bb1c6e9088e32a55eb82c upstream.
uevent_show() wants to de-reference dev->driver->name. There is no clean
way for a device attribute to de-reference dev->driver unless that
attribute is defined via (struct device_driver).dev_groups. Instead, the
anti-pattern of taking the device_lock() in the attribute handler risks
deadlocks with code paths that remove device attributes while holding
the lock.
This deadlock is typically invisible to lockdep given the device_lock()
is marked lockdep_set_novalidate_class(), but some subsystems allocate a
local lockdep key for @dev->mutex to reveal reports of the form:
======================================================
WARNING: possible circular locking dependency detected
6.10.0-rc7+ #275 Tainted: G OE N
------------------------------------------------------
modprobe/2374 is trying to acquire lock:
ffff8c2270070de0 (kn->active#6){++++}-{0:0}, at: __kernfs_remove+0xde/0x220
but task is already holding lock:
ffff8c22016e88f8 (&cxl_root_key){+.+.}-{3:3}, at: device_release_driver_internal+0x39/0x210
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
-> #1 (&cxl_root_key){+.+.}-{3:3}:
__mutex_lock+0x99/0xc30
uevent_show+0xac/0x130
dev_attr_show+0x18/0x40
sysfs_kf_seq_show+0xac/0xf0
seq_read_iter+0x110/0x450
vfs_read+0x25b/0x340
ksys_read+0x67/0xf0
do_syscall_64+0x75/0x190
entry_SYSCALL_64_after_hwframe+0x76/0x7e
-> #0 (kn->active#6){++++}-{0:0}:
__lock_acquire+0x121a/0x1fa0
lock_acquire+0xd6/0x2e0
kernfs_drain+0x1e9/0x200
__kernfs_remove+0xde/0x220
kernfs_remove_by_name_ns+0x5e/0xa0
device_del+0x168/0x410
device_unregister+0x13/0x60
devres_release_all+0xb8/0x110
device_unbind_cleanup+0xe/0x70
device_release_driver_internal+0x1c7/0x210
driver_detach+0x47/0x90
bus_remove_driver+0x6c/0xf0
cxl_acpi_exit+0xc/0x11 [cxl_acpi]
__do_sys_delete_module.isra.0+0x181/0x260
do_syscall_64+0x75/0x190
entry_SYSCALL_64_after_hwframe+0x76/0x7e
The observation though is that driver objects are typically much longer
lived than device objects. It is reasonable to perform lockless
de-reference of a @driver pointer even if it is racing detach from a
device. Given the infrequency of driver unregistration, use
synchronize_rcu() in module_remove_driver() to close any potential
races. It is potentially overkill to suffer synchronize_rcu() just to
handle the rare module removal racing uevent_show() event.
Thanks to Tetsuo Handa for the debug analysis of the syzbot report [1].
Fixes: c0a40097f0bc ("drivers: core: synchronize really_probe() and dev_uevent()")
Reported-by: syzbot+4762dd74e32532cda5ff@syzkaller.appspotmail.com
Reported-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Closes: http://lore.kernel.org/5aa5558f-90a4-4864-b1b1-5d6784c5607d@I-love.SAKURA.ne.jp [1]
Link: http://lore.kernel.org/669073b8ea479_5fffa294c1@dwillia2-xfh.jf.intel.com.notmuch
Cc: stable@vger.kernel.org
Cc: Ashish Sangwan <a.sangwan@samsung.com>
Cc: Namjae Jeon <namjae.jeon@samsung.com>
Cc: Dirk Behme <dirk.behme@de.bosch.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Rafael J. Wysocki <rafael@kernel.org>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Link: https://lore.kernel.org/r/172081332794.577428.9738802016494057132.stgit@dwillia2-xfh.jf.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
commit c0a40097f0bc81deafc15f9195d1fb54595cd6d0 upstream.
Synchronize the dev->driver usage in really_probe() and dev_uevent().
These can run in different threads, what can result in the following
race condition for dev->driver uninitialization:
Thread #1:
==========
really_probe() {
...
probe_failed:
...
device_unbind_cleanup(dev) {
...
dev->driver = NULL; // <= Failed probe sets dev->driver to NULL
...
}
...
}
Thread #2:
==========
dev_uevent() {
...
if (dev->driver)
// If dev->driver is NULLed from really_probe() from here on,
// after above check, the system crashes
add_uevent_var(env, "DRIVER=%s", dev->driver->name);
...
}
really_probe() holds the lock, already. So nothing needs to be done
there. dev_uevent() is called with lock held, often, too. But not
always. What implies that we can't add any locking in dev_uevent()
itself. So fix this race by adding the lock to the non-protected
path. This is the path where above race is observed:
dev_uevent+0x235/0x380
uevent_show+0x10c/0x1f0 <= Add lock here
dev_attr_show+0x3a/0xa0
sysfs_kf_seq_show+0x17c/0x250
kernfs_seq_show+0x7c/0x90
seq_read_iter+0x2d7/0x940
kernfs_fop_read_iter+0xc6/0x310
vfs_read+0x5bc/0x6b0
ksys_read+0xeb/0x1b0
__x64_sys_read+0x42/0x50
x64_sys_call+0x27ad/0x2d30
do_syscall_64+0xcd/0x1d0
entry_SYSCALL_64_after_hwframe+0x77/0x7f
Similar cases are reported by syzkaller in
https://syzkaller.appspot.com/bug?extid=ffa8143439596313a85a
But these are regarding the *initialization* of dev->driver
dev->driver = drv;
As this switches dev->driver to non-NULL these reports can be considered
to be false-positives (which should be "fixed" by this commit, as well,
though).
The same issue was reported and tried to be fixed back in 2015 in
https://lore.kernel.org/lkml/1421259054-2574-1-git-send-email-a.sangwan@samsung.com/
already.
Fixes: 239378f16aa1 ("Driver core: add uevent vars for devices of a class")
Cc: stable <stable@kernel.org>
Cc: syzbot+ffa8143439596313a85a@syzkaller.appspotmail.com
Cc: Ashish Sangwan <a.sangwan@samsung.com>
Cc: Namjae Jeon <namjae.jeon@samsung.com>
Signed-off-by: Dirk Behme <dirk.behme@de.bosch.com>
Link: https://lore.kernel.org/r/20240513050634.3964461-1-dirk.behme@de.bosch.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
[ Upstream commit 70f400d4d957c2453c8689552ff212bc59f88938 ]
Move the "removable" attribute from USB to core in order to allow it to be
supported by other subsystem / buses. Individual buses that want to support
this attribute can populate the removable property of the device while
enumerating it with the 3 possible values -
- "unknown"
- "fixed"
- "removable"
Leaving the field unchanged (i.e. "not supported") would mean that the
attribute would not show up in sysfs for that device. The UAPI (location,
symantics etc) for the attribute remains unchanged.
Move the "removable" attribute from USB to the device core so it can be
used by other subsystems / buses.
By default, devices do not have a "removable" attribute in sysfs.
If a subsystem or bus driver wants to support a "removable" attribute, it
should call device_set_removable() before calling device_register() or
device_add(), e.g.:
device_set_removable(dev, DEVICE_REMOVABLE);
device_register(dev);
The possible values and the resulting sysfs attribute contents are:
DEVICE_REMOVABLE_UNKNOWN -> "unknown"
DEVICE_REMOVABLE -> "removable"
DEVICE_FIXED -> "fixed"
Convert the USB "removable" attribute to use this new device core
functionality. There should be no user-visible change in the location or
semantics of attribute for USB devices.
Reviewed-by: Bjorn Helgaas <bhelgaas@google.com>
Signed-off-by: Rajat Jain <rajatja@google.com>
Link: https://lore.kernel.org/r/20210524171812.18095-1-rajatja@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Stable-dep-of: 432e664e7c98 ("drm/amdgpu: don't use ATRM for external devices")
Signed-off-by: Sasha Levin <sashal@kernel.org>
