{"id":"CVE-2024-56672","summary":"blk-cgroup: Fix UAF in blkcg_unpin_online()","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   \u003cTASK\u003e\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   \u003c/TASK\u003e\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.","modified":"2026-04-02T12:25:06.264879Z","published":"2024-12-27T15:06:33.358Z","related":["ALSA-2025:20518","MGASA-2025-0030","MGASA-2025-0032","SUSE-SU-2025:0289-1","SUSE-SU-2025:0428-1","SUSE-SU-2025:0499-1","SUSE-SU-2025:0557-1","SUSE-SU-2025:20165-1","SUSE-SU-2025:20166-1","SUSE-SU-2025:20248-1","SUSE-SU-2025:20249-1","USN-7323-2","USN-7380-1"],"database_specific":{"cna_assigner":"Linux","osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2024/56xxx/CVE-2024-56672.json"},"references":[{"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"},{"type":"WEB","url":"https://lists.debian.org/debian-lts-announce/2025/03/msg00001.html"},{"type":"WEB","url":"https://lists.debian.org/debian-lts-announce/2025/03/msg00002.html"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2024/56xxx/CVE-2024-56672.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2024-56672"},{"type":"PACKAGE","url":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"4308a434e5e08c78676aa66bc626ef78cbef0883"},{"fixed":"83f5a87ee8caa76a917f59912a74d6811f773c67"},{"fixed":"8a07350fe070017a887433f4d6909433955be5f1"},{"fixed":"64afc6fe24c9896c0153e5a199bcea241ecb0d5c"},{"fixed":"5baa28569c924d9a90d036c2aaab79f791fedaf8"},{"fixed":"29d1e06560f0f6179062ac638b4064deb637d1ad"},{"fixed":"86e6ca55b83c575ab0f2e105cf08f98e58d3d7af"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2024-56672.json"}}],"schema_version":"1.7.5","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H"}]}