ghsa-qgw7-mg2m-3x6f
Vulnerability from github
Published
2024-12-27 15:31
Modified
2025-02-02 12:30
Severity ?
7.0 (High) - CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
Details

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: 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 ... 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.

Show details on source website

To clipboard 

{
   affected: [],
   aliases: [
      "CVE-2024-56672",
   ],
   database_specific: {
      cwe_ids: [
         "CWE-416",
      ],
      github_reviewed: false,
      github_reviewed_at: null,
      nvd_published_at: "2024-12-27T15:15:27Z",
      severity: "HIGH",
   },
   details: "In the Linux kernel, the following vulnerability has been resolved:\n\nblk-cgroup: Fix UAF in blkcg_unpin_online()\n\nblkcg_unpin_online() walks up the blkcg hierarchy putting the online pin. To\nwalk up, it uses blkcg_parent(blkcg) but it was calling that after\nblkcg_destroy_blkgs(blkcg) which could free the blkcg, leading to the\nfollowing UAF:\n\n  ==================================================================\n  BUG: KASAN: slab-use-after-free in blkcg_unpin_online+0x15a/0x270\n  Read of size 8 at addr ffff8881057678c0 by task kworker/9:1/117\n\n  CPU: 9 UID: 0 PID: 117 Comm: kworker/9:1 Not tainted 6.13.0-rc1-work-00182-gb8f52214c61a-dirty #48\n  Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS unknown 02/02/2022\n  Workqueue: cgwb_release cgwb_release_workfn\n  Call Trace:\n   <TASK>\n   dump_stack_lvl+0x27/0x80\n   print_report+0x151/0x710\n   kasan_report+0xc0/0x100\n   blkcg_unpin_online+0x15a/0x270\n   cgwb_release_workfn+0x194/0x480\n   process_scheduled_works+0x71b/0xe20\n   worker_thread+0x82a/0xbd0\n   kthread+0x242/0x2c0\n   ret_from_fork+0x33/0x70\n   ret_from_fork_asm+0x1a/0x30\n   </TASK>\n  ...\n  Freed by task 1944:\n   kasan_save_track+0x2b/0x70\n   kasan_save_free_info+0x3c/0x50\n   __kasan_slab_free+0x33/0x50\n   kfree+0x10c/0x330\n   css_free_rwork_fn+0xe6/0xb30\n   process_scheduled_works+0x71b/0xe20\n   worker_thread+0x82a/0xbd0\n   kthread+0x242/0x2c0\n   ret_from_fork+0x33/0x70\n   ret_from_fork_asm+0x1a/0x30\n\nNote that the UAF is not easy to trigger as the free path is indirected\nbehind a couple RCU grace periods and a work item execution. I could only\ntrigger it with artifical msleep() injected in blkcg_unpin_online().\n\nFix it by reading the parent pointer before destroying the blkcg's blkg's.",
   id: "GHSA-qgw7-mg2m-3x6f",
   modified: "2025-02-02T12:30:24Z",
   published: "2024-12-27T15:31:56Z",
   references: [
      {
         type: "ADVISORY",
         url: "https://nvd.nist.gov/vuln/detail/CVE-2024-56672",
      },
      {
         type: "WEB",
         url: "https://git.kernel.org/stable/c/29d1e06560f0f6179062ac638b4064deb637d1ad",
      },
      {
         type: "WEB",
         url: "https://git.kernel.org/stable/c/5baa28569c924d9a90d036c2aaab79f791fedaf8",
      },
      {
         type: "WEB",
         url: "https://git.kernel.org/stable/c/64afc6fe24c9896c0153e5a199bcea241ecb0d5c",
      },
      {
         type: "WEB",
         url: "https://git.kernel.org/stable/c/83f5a87ee8caa76a917f59912a74d6811f773c67",
      },
      {
         type: "WEB",
         url: "https://git.kernel.org/stable/c/86e6ca55b83c575ab0f2e105cf08f98e58d3d7af",
      },
      {
         type: "WEB",
         url: "https://git.kernel.org/stable/c/8a07350fe070017a887433f4d6909433955be5f1",
      },
   ],
   schema_version: "1.4.0",
   severity: [
      {
         score: "CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H",
         type: "CVSS_V3",
      },
   ],
}


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