Homepage

Use After Free Affecting kernel-rt-debug-modules-core package, versions *

Severity

 Recommended
medium

Based on Red Hat Enterprise Linux security rating.

Threat Intelligence

EPSS
0.04% (6th percentile)

Do your applications use this vulnerable package?

In a few clicks we can analyze your entire application and see what components are vulnerable in your application, and suggest you quick fixes.

Test your applications

Snyk Learn

Learn about Use After Free vulnerabilities in an interactive lesson.

Start learning
  • Snyk IDSNYK-RHEL9-KERNELRTDEBUGMODULESCORE-7589743
  • published5 Aug 2024
  • disclosed29 Jul 2024
Report a new vulnerability Found a mistake?

Introduced: 29 Jul 2024

CVE-2024-41057  (opens in a new tab)
CWE-416  (opens in a new tab)
First added by Snyk

How to fix?

There is no fixed version for RHEL:9 kernel-rt-debug-modules-core.

NVD Description

Note: Versions mentioned in the description apply only to the upstream kernel-rt-debug-modules-core package and not the kernel-rt-debug-modules-core package as distributed by RHEL. See How to fix? for RHEL:9 relevant fixed versions and status.

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

cachefiles: fix slab-use-after-free in cachefiles_withdraw_cookie()

We got the following issue in our fault injection stress test:

================================================================== BUG: KASAN: slab-use-after-free in cachefiles_withdraw_cookie+0x4d9/0x600 Read of size 8 at addr ffff888118efc000 by task kworker/u78:0/109

CPU: 13 PID: 109 Comm: kworker/u78:0 Not tainted 6.8.0-dirty #566 Call Trace: <TASK> kasan_report+0x93/0xc0 cachefiles_withdraw_cookie+0x4d9/0x600 fscache_cookie_state_machine+0x5c8/0x1230 fscache_cookie_worker+0x91/0x1c0 process_one_work+0x7fa/0x1800 [...]

Allocated by task 117: kmalloc_trace+0x1b3/0x3c0 cachefiles_acquire_volume+0xf3/0x9c0 fscache_create_volume_work+0x97/0x150 process_one_work+0x7fa/0x1800 [...]

Freed by task 120301: kfree+0xf1/0x2c0 cachefiles_withdraw_cache+0x3fa/0x920 cachefiles_put_unbind_pincount+0x1f6/0x250 cachefiles_daemon_release+0x13b/0x290 __fput+0x204/0xa00 task_work_run+0x139/0x230 do_exit+0x87a/0x29b0 [...]

Following is the process that triggers the issue:

       p1                |             p2

                          fscache_begin_lookup
                           fscache_begin_volume_access
                            fscache_cache_is_live(fscache_cache)

cachefiles_daemon_release cachefiles_put_unbind_pincount cachefiles_daemon_unbind cachefiles_withdraw_cache fscache_withdraw_cache fscache_set_cache_state(cache, FSCACHE_CACHE_IS_WITHDRAWN); cachefiles_withdraw_objects(cache) fscache_wait_for_objects(fscache) atomic_read(&fscache_cache->object_count) == 0 fscache_perform_lookup cachefiles_lookup_cookie cachefiles_alloc_object refcount_set(&object->ref, 1); object->volume = volume fscache_count_object(vcookie->cache); atomic_inc(&fscache_cache->object_count) cachefiles_withdraw_volumes cachefiles_withdraw_volume fscache_withdraw_volume __cachefiles_free_volume kfree(cachefiles_volume) fscache_cookie_state_machine cachefiles_withdraw_cookie cache = object->volume->cache; // cachefiles_volume UAF !!!

After setting FSCACHE_CACHE_IS_WITHDRAWN, wait for all the cookie lookups to complete first, and then wait for fscache_cache->object_count == 0 to avoid the cookie exiting after the volume has been freed and triggering the above issue. Therefore call fscache_withdraw_volume() before calling cachefiles_withdraw_objects().

This way, after setting FSCACHE_CACHE_IS_WITHDRAWN, only the following two cases will occur:

  1. fscache_begin_lookup fails in fscache_begin_volume_access().
  2. fscache_withdraw_volume() will ensure that fscache_count_object() has been executed before calling fscache_wait_for_objects().

CVSS Scores

version 3.1