7.8

CVE-2024-56672

blk-cgroup: Fix UAF in blkcg_unpin_online()

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

blk-cgroup: Fix UAF in blkcg_unpin_online()

blkcg_unpin_online() walks up the blkcg hierarchy putting the online pin. To
walk up, it uses blkcg_parent(blkcg) but it was calling that after
blkcg_destroy_blkgs(blkcg) which could free the blkcg, leading to the
following UAF:

  ==================================================================
  BUG: KASAN: slab-use-after-free in blkcg_unpin_online+0x15a/0x270
  Read of size 8 at addr ffff8881057678c0 by task kworker/9:1/117

  CPU: 9 UID: 0 PID: 117 Comm: kworker/9:1 Not tainted 6.13.0-rc1-work-00182-gb8f52214c61a-dirty #48
  Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS unknown 02/02/2022
  Workqueue: cgwb_release cgwb_release_workfn
  Call Trace:
   <TASK>
   dump_stack_lvl+0x27/0x80
   print_report+0x151/0x710
   kasan_report+0xc0/0x100
   blkcg_unpin_online+0x15a/0x270
   cgwb_release_workfn+0x194/0x480
   process_scheduled_works+0x71b/0xe20
   worker_thread+0x82a/0xbd0
   kthread+0x242/0x2c0
   ret_from_fork+0x33/0x70
   ret_from_fork_asm+0x1a/0x30
   </TASK>
  ...
  Freed by task 1944:
   kasan_save_track+0x2b/0x70
   kasan_save_free_info+0x3c/0x50
   __kasan_slab_free+0x33/0x50
   kfree+0x10c/0x330
   css_free_rwork_fn+0xe6/0xb30
   process_scheduled_works+0x71b/0xe20
   worker_thread+0x82a/0xbd0
   kthread+0x242/0x2c0
   ret_from_fork+0x33/0x70
   ret_from_fork_asm+0x1a/0x30

Note that the UAF is not easy to trigger as the free path is indirected
behind a couple RCU grace periods and a work item execution. I could only
trigger it with artifical msleep() injected in blkcg_unpin_online().

Fix it by reading the parent pointer before destroying the blkcg's blkg's.
Daten sind bereitgestellt durch National Vulnerability Database (NVD)
Linux ≫ Linux Kernel Version >= 5.7 < 6.1.121
Linux ≫ Linux Kernel Version >= 6.2 < 6.6.67
Linux ≫ Linux Kernel Version >= 6.7 < 6.12.6
Linux ≫ Linux Kernel Version6.13 Updaterc1
Linux ≫ Linux Kernel Version6.13 Updaterc2
VulnDex Vulnerability Enrichment
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Zu dieser CVE wurde keine Warnung gefunden.
EPSS Metriken
Typ Quelle Score Percentile
EPSS FIRST.org 0.27% 0.186
CVSS Metriken
Quelle Base Score Exploit Score Impact Score Vector String
nvd@nist.gov 7 1 5.9
CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
134c704f-9b21-4f2e-91b3-4a467353bcc0 7.8 1.8 5.9
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
CWE-416 Use After Free

The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory "belongs" to the code that operates on the new pointer.

https://git.kernel.org/stable/c/29d1e06560f0f6179062ac638b4064deb637d1ad
Patch
https://git.kernel.org/stable/c/5baa28569c924d9a90d036c2aaab79f791fedaf8
Patch
https://git.kernel.org/stable/c/64afc6fe24c9896c0153e5a199bcea241ecb0d5c
Patch
https://git.kernel.org/stable/c/83f5a87ee8caa76a917f59912a74d6811f773c67
https://git.kernel.org/stable/c/86e6ca55b83c575ab0f2e105cf08f98e58d3d7af
Patch
https://git.kernel.org/stable/c/8a07350fe070017a887433f4d6909433955be5f1
https://lists.debian.org/debian-lts-announce/2025/03/msg00001.html
https://lists.debian.org/debian-lts-announce/2025/03/msg00002.html
https://cert-portal.siemens.com/productcert/html/ssa-265688.html