CVE-2024-44952 driver core: Fix uevent_show() vs driver detach race

2024-09-0418:35:52

Linux

www.cve.org

linux kernel

driver core

uevent_show

driver detach race

deadlock

synchronize_rcu

module removal

EPSS

Percentile

5.1%

JSON

In the Linux kernel, the following vulnerability has been resolved:

driver core: Fix uevent_show() vs driver detach race

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].

CNA Affected

[
  {
    "product": "Linux",
    "vendor": "Linux",
    "defaultStatus": "unaffected",
    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
    "programFiles": [
      "drivers/base/core.c",
      "drivers/base/module.c"
    ],
    "versions": [
      {
        "version": "bb3641a58317",
        "lessThan": "49ea4e0d8626",
        "status": "affected",
        "versionType": "git"
      },
      {
        "version": "13d25e82b6d0",
        "lessThan": "dd98c9630b7e",
        "status": "affected",
        "versionType": "git"
      },
      {
        "version": "760603e30bf1",
        "lessThan": "f098e8fc7227",
        "status": "affected",
        "versionType": "git"
      },
      {
        "version": "ec772ed7cb21",
        "lessThan": "9c23fc327d6e",
        "status": "affected",
        "versionType": "git"
      },
      {
        "version": "08891eeaa97c",
        "lessThan": "4a7c2a838752",
        "status": "affected",
        "versionType": "git"
      },
      {
        "version": "a42b0060d6ff",
        "lessThan": "4d035c743c3e",
        "status": "affected",
        "versionType": "git"
      },
      {
        "version": "c0a40097f0bc",
        "lessThan": "cd490a247ddf",
        "status": "affected",
        "versionType": "git"
      },
      {
        "version": "c0a40097f0bc",
        "lessThan": "15fffc6a5624",
        "status": "affected",
        "versionType": "git"
      }
    ]
  },
  {
    "product": "Linux",
    "vendor": "Linux",
    "defaultStatus": "affected",
    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
    "programFiles": [
      "drivers/base/core.c",
      "drivers/base/module.c"
    ],
    "versions": [
      {
        "version": "6.10",
        "status": "affected"
      },
      {
        "version": "0",
        "lessThan": "6.10",
        "status": "unaffected",
        "versionType": "custom"
      },
      {
        "version": "4.19.320",
        "lessThanOrEqual": "4.19.*",
        "status": "unaffected",
        "versionType": "custom"
      },
      {
        "version": "5.4.282",
        "lessThanOrEqual": "5.4.*",
        "status": "unaffected",
        "versionType": "custom"
      },
      {
        "version": "5.10.224",
        "lessThanOrEqual": "5.10.*",
        "status": "unaffected",
        "versionType": "custom"
      },
      {
        "version": "5.15.165",
        "lessThanOrEqual": "5.15.*",
        "status": "unaffected",
        "versionType": "custom"
      },
      {
        "version": "6.1.105",
        "lessThanOrEqual": "6.1.*",
        "status": "unaffected",
        "versionType": "custom"
      },
      {
        "version": "6.6.46",
        "lessThanOrEqual": "6.6.*",
        "status": "unaffected",
        "versionType": "custom"
      },
      {
        "version": "6.10.5",
        "lessThanOrEqual": "6.10.*",
        "status": "unaffected",
        "versionType": "custom"
      },
      {
        "version": "6.11",
        "lessThanOrEqual": "*",
        "status": "unaffected",
        "versionType": "original_commit_for_fix"
      }
    ]
  }
]