{"id":"DEBIAN-CVE-2024-56672","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:    \u003cTASK\u003e    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    \u003c/TASK\u003e   ...   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.","modified":"2026-09-15T09:03:17.216862802Z","published":"2024-12-27T15:15:27.107Z","upstream":["CVE-2024-56672"],"references":[{"type":"ADVISORY","url":"https://security-tracker.debian.org/tracker/CVE-2024-56672"}],"affected":[{"package":{"name":"linux","ecosystem":"Debian:12","purl":"pkg:deb/debian/linux?arch=source&distro=bookworm"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"6.1.123-1"}]}],"versions":["6.1.106-1","6.1.106-2","6.1.106-3","6.1.112-1","6.1.115-1","6.1.119-1","6.1.27-1","6.1.37-1","6.1.38-1","6.1.38-2","6.1.38-2~bpo11+1","6.1.38-3","6.1.38-4","6.1.38-4~bpo11+1","6.1.52-1","6.1.55-1","6.1.55-1~bpo11+1","6.1.64-1","6.1.66-1","6.1.67-1","6.1.69-1","6.1.69-1~bpo11+1","6.1.76-1","6.1.76-1~bpo11+1","6.1.82-1","6.1.85-1","6.1.90-1","6.1.90-1~bpo11+1","6.1.94-1","6.1.94-1~bpo11+1","6.1.98-1","6.1.99-1"],"ecosystem_specific":{"urgency":"not yet assigned"},"database_specific":{"source":"https://storage.googleapis.com/osv-test-debian-osv/debian-cve-osv/DEBIAN-CVE-2024-56672.json"}},{"package":{"name":"linux","ecosystem":"Debian:13","purl":"pkg:deb/debian/linux?arch=source&distro=trixie"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"6.12.6-1"}]}],"ecosystem_specific":{"urgency":"not yet assigned"},"database_specific":{"source":"https://storage.googleapis.com/osv-test-debian-osv/debian-cve-osv/DEBIAN-CVE-2024-56672.json"}},{"package":{"name":"linux","ecosystem":"Debian:14","purl":"pkg:deb/debian/linux?arch=source&distro=forky"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"6.12.6-1"}]}],"ecosystem_specific":{"urgency":"not yet assigned"},"database_specific":{"source":"https://storage.googleapis.com/osv-test-debian-osv/debian-cve-osv/DEBIAN-CVE-2024-56672.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H"}]}