linux-stable.git/drivers/base/core.c, branch linux-6.11.y

cxl/port: Fix use-after-free, permit out-of-order decoder shutdown

2024-11-08T15:30:56+00:00

commit 101c268bd2f37e965a5468353e62d154db38838e upstream.

In support of investigating an initialization failure report [1],
cxl_test was updated to register mock memory-devices after the mock
root-port/bus device had been registered. That led to cxl_test crashing
with a use-after-free bug with the following signature:

    cxl_port_attach_region: cxl region3: cxl_host_bridge.0:port3 decoder3.0 add: mem0:decoder7.0 @ 0 next: cxl_switch_uport.0 nr_eps: 1 nr_targets: 1
    cxl_port_attach_region: cxl region3: cxl_host_bridge.0:port3 decoder3.0 add: mem4:decoder14.0 @ 1 next: cxl_switch_uport.0 nr_eps: 2 nr_targets: 1
    cxl_port_setup_targets: cxl region3: cxl_switch_uport.0:port6 target[0] = cxl_switch_dport.0 for mem0:decoder7.0 @ 0
1)  cxl_port_setup_targets: cxl region3: cxl_switch_uport.0:port6 target[1] = cxl_switch_dport.4 for mem4:decoder14.0 @ 1
    [..]
    cxld_unregister: cxl decoder14.0:
    cxl_region_decode_reset: cxl_region region3:
    mock_decoder_reset: cxl_port port3: decoder3.0 reset
2)  mock_decoder_reset: cxl_port port3: decoder3.0: out of order reset, expected decoder3.1
    cxl_endpoint_decoder_release: cxl decoder14.0:
    [..]
    cxld_unregister: cxl decoder7.0:
3)  cxl_region_decode_reset: cxl_region region3:
    Oops: general protection fault, probably for non-canonical address 0x6b6b6b6b6b6b6bc3: 0000 [#1] PREEMPT SMP PTI
    [..]
    RIP: 0010:to_cxl_port+0x8/0x60 [cxl_core]
    [..]
    Call Trace:
     
     cxl_region_decode_reset+0x69/0x190 [cxl_core]
     cxl_region_detach+0xe8/0x210 [cxl_core]
     cxl_decoder_kill_region+0x27/0x40 [cxl_core]
     cxld_unregister+0x5d/0x60 [cxl_core]

At 1) a region has been established with 2 endpoint decoders (7.0 and
14.0). Those endpoints share a common switch-decoder in the topology
(3.0). At teardown, 2), decoder14.0 is the first to be removed and hits
the "out of order reset case" in the switch decoder. The effect though
is that region3 cleanup is aborted leaving it in-tact and
referencing decoder14.0. At 3) the second attempt to teardown region3
trips over the stale decoder14.0 object which has long since been
deleted.

The fix here is to recognize that the CXL specification places no
mandate on in-order shutdown of switch-decoders, the driver enforces
in-order allocation, and hardware enforces in-order commit. So, rather
than fail and leave objects dangling, always remove them.

In support of making cxl_region_decode_reset() always succeed,
cxl_region_invalidate_memregion() failures are turned into warnings.
Crashing the kernel is ok there since system integrity is at risk if
caches cannot be managed around physical address mutation events like
CXL region destruction.

A new device_for_each_child_reverse_from() is added to cleanup
port->commit_end after all dependent decoders have been disabled. In
other words if decoders are allocated 0->1->2 and disabled 1->2->0 then
port->commit_end only decrements from 2 after 2 has been disabled, and
it decrements all the way to zero since 1 was disabled previously.

Link: http://lore.kernel.org/20241004212504.1246-1-gourry@gourry.net [1]
Cc: stable@vger.kernel.org
Fixes: 176baefb2eb5 ("cxl/hdm: Commit decoder state to hardware")
Reviewed-by: Jonathan Cameron 
Cc: Greg Kroah-Hartman 
Cc: Davidlohr Bueso 
Cc: Dave Jiang 
Cc: Alison Schofield 
Cc: Ira Weiny 
Cc: Zijun Hu 
Signed-off-by: Dan Williams 
Reviewed-by: Ira Weiny 
Link: https://patch.msgid.link/172964782781.81806.17902885593105284330.stgit@dwillia2-xfh.jf.intel.com
Signed-off-by: Ira Weiny 
Signed-off-by: Greg Kroah-Hartman

Revert "driver core: Fix uevent_show() vs driver detach race"

2024-11-08T15:30:54+00:00

commit 9a71892cbcdb9d1459c84f5a4c722b14354158a5 upstream.

This reverts commit 15fffc6a5624b13b428bb1c6e9088e32a55eb82c.

This commit causes a regression, so revert it for now until it can come
back in a way that works for everyone.

Link: https://lore.kernel.org/all/172790598832.1168608.4519484276671503678.stgit@dwillia2-xfh.jf.intel.com/
Fixes: 15fffc6a5624 ("driver core: Fix uevent_show() vs driver detach race")
Cc: stable 
Cc: Ashish Sangwan 
Cc: Namjae Jeon 
Cc: Dirk Behme 
Cc: Greg Kroah-Hartman 
Cc: Rafael J. Wysocki 
Cc: Dan Williams 
Signed-off-by: Greg Kroah-Hartman

driver core: Fix error handling in driver API device_rename()

2024-10-04T14:38:21+00:00

[ Upstream commit 6d8249ac29bc23260dfa9747eb398ce76012d73c ]

For class-device, device_rename() failure maybe cause unexpected link name
within its class folder as explained below:

/sys/class/.../old_name -> /sys/devices/.../old_name
device_rename(..., new_name) and failed
/sys/class/.../new_name -> /sys/devices/.../old_name

Fixed by undoing renaming link if renaming kobject failed.

Fixes: f349cf34731c ("driver core: Implement ns directory support for device classes.")
Signed-off-by: Zijun Hu 
Link: https://lore.kernel.org/r/20240722-device_rename_fix-v2-1-77de1a6c6495@quicinc.com
Signed-off-by: Greg Kroah-Hartman 
Signed-off-by: Sasha Levin

driver core: Fix uevent_show() vs driver detach race

2024-07-31T12:41:44+00:00

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 
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 
Cc: Namjae Jeon 
Cc: Dirk Behme 
Cc: Greg Kroah-Hartman 
Cc: Rafael J. Wysocki 
Signed-off-by: Dan Williams 
Link: https://lore.kernel.org/r/172081332794.577428.9738802016494057132.stgit@dwillia2-xfh.jf.intel.com
Signed-off-by: Greg Kroah-Hartman

driver core: Make dev_err_probe() silent for -ENOMEM

2024-06-20T10:48:09+00:00

For an out-of-memory error there should be no additional output. Adapt
dev_err_probe() to not emit the error message when err is -ENOMEM.
This simplifies handling errors that might among others be -ENOMEM.

Signed-off-by: Uwe Kleine-König 
Reviewed-by: Geert Uytterhoeven 
Link: https://lore.kernel.org/r/3d1e308d45cddf67749522ca42d83f5b4f0b9634.1718311756.git.u.kleine-koenig@baylibre.com
Signed-off-by: Greg Kroah-Hartman

drivers: core: synchronize really_probe() and dev_uevent()

2024-06-04T16:14:51+00:00

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 
Cc: syzbot+ffa8143439596313a85a@syzkaller.appspotmail.com
Cc: Ashish Sangwan 
Cc: Namjae Jeon 
Signed-off-by: Dirk Behme 
Link: https://lore.kernel.org/r/20240513050634.3964461-1-dirk.behme@de.bosch.com
Signed-off-by: Greg Kroah-Hartman

driver core: remove devm_device_add_groups()

2024-06-04T13:53:36+00:00

There is no more in-kernel users of this function, and no driver should
ever be using it, so remove it from the kernel.

Acked-by: Dmitry Torokhov 
Acked-by: "Rafael J. Wysocki" 
Link: https://lore.kernel.org/r/20230704131715.44454-8-gregkh@linuxfoundation.org
Signed-off-by: Greg Kroah-Hartman

driver core: Add device_show_string() helper for sysfs attributes

2024-05-04T15:37:03+00:00

For drivers wishing to expose an unsigned long, int or bool at a static
memory location in sysfs, the driver core provides ready-made helpers
such as device_show_ulong() to be used as ->show() callback.

Some drivers need to expose a string and so far they all provide their
own ->show() implementation.  arch/powerpc/perf/hv-24x7.c went so far
as to create a device_show_string() helper but kept it private.

Make it public for reuse by other drivers.  The pattern seems to be
sufficiently frequent to merit a public helper.

Add a DEVICE_STRING_ATTR_RO() macro in line with the existing
DEVICE_ULONG_ATTR() and similar macros to ease declaration of string
attributes.

Signed-off-by: Lukas Wunner 
Acked-by: Michael Ellerman 
Link: https://lore.kernel.org/r/2e3eaaf2600bb55c0415c23ba301e809403a7aa2.1713608122.git.lukas@wunner.de
Signed-off-by: Greg Kroah-Hartman

Merge 6.9-rc5 into driver-core-next

2024-04-23T11:27:43+00:00

We want the kernfs fixes in here as well.

Signed-off-by: Greg Kroah-Hartman

driver core: Remove unused platform_notify, platform_notify_remove

2024-03-27T07:01:12+00:00

The "platform_notify" and "platform_notify_remove" hooks have been unused
since 00ba9357d189 ("ARM: ixp4xx: Drop custom DMA coherency and bouncing").

Remove "platform_notify" and "platform_notify_remove".  No functional
change intended.

Signed-off-by: Bjorn Helgaas 
Cc: Heikki Krogerus 
Cc: Linus Walleij 
Reviewed-by: Andy Shevchenko 
Acked-by: Rafael J. Wysocki 
Link: https://lore.kernel.org/r/20240325221409.1457036-1-helgaas@kernel.org
Signed-off-by: Greg Kroah-Hartman