UBUNTU-CVE-2024-56672
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.
02 / AFFECTED SOFTWARE
Affected packages
6 explicit affected versions
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35 explicit affected versions
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19 explicit affected versions
42 explicit affected versions
20 explicit affected versions
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1 explicit affected versions
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51 explicit affected versions
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10 explicit affected versions
37 explicit affected versions
1 explicit affected versions
35 explicit affected versions
26 explicit affected versions
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65 explicit affected versions
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7 explicit affected versions
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51 explicit affected versions
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10 explicit affected versions
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10 explicit affected versions
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13 explicit affected versions
20 explicit affected versions
16 explicit affected versions
63 explicit affected versions
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3 explicit affected versions
1 explicit affected versions
2 explicit affected versions
51 explicit affected versions
27 explicit affected versions
8 explicit affected versions
20 explicit affected versions
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48 explicit affected versions
13 explicit affected versions
7 explicit affected versions
2 explicit affected versions
53 explicit affected versions
10 explicit affected versions
12 explicit affected versions
15 explicit affected versions
44 explicit affected versions
16 explicit affected versions
11 explicit affected versions
13 explicit affected versions
26 explicit affected versions
45 explicit affected versions
37 explicit affected versions
14 explicit affected versions
38 explicit affected versions
52 explicit affected versions
9 explicit affected versions
51 explicit affected versions
14 explicit affected versions
7 explicit affected versions
61 explicit affected versions
7 explicit affected versions
33 explicit affected versions
1 explicit affected versions
1 explicit affected versions
1 explicit affected versions
59 explicit affected versions
13 explicit affected versions
14 explicit affected versions
43 explicit affected versions
10 explicit affected versions
8 explicit affected versions
18 explicit affected versions
14 explicit affected versions
4 explicit affected versions
78 explicit affected versions
11 explicit affected versions
1 explicit affected versions
03 / CONNECTIONS
Connected vulnerabilities
04 / EVIDENCE
Source records
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.
05 / REFERENCES
Further evidence
- https://git.kernel.org/linus/86e6ca55b83c575ab0f2e105cf08f98e58d3d7af
- https://git.kernel.org/stable/c/29d1e06560f0f6179062ac638b4064deb637d1ad
- https://git.kernel.org/stable/c/5baa28569c924d9a90d036c2aaab79f791fedaf8
- https://git.kernel.org/stable/c/64afc6fe24c9896c0153e5a199bcea241ecb0d5c
- https://git.kernel.org/stable/c/86e6ca55b83c575ab0f2e105cf08f98e58d3d7af
- https://ubuntu.com/security/CVE-2024-56672
- https://ubuntu.com/security/notices/USN-7322-1
- https://ubuntu.com/security/notices/USN-7323-1
- https://ubuntu.com/security/notices/USN-7323-2
- https://ubuntu.com/security/notices/USN-7327-1
- https://ubuntu.com/security/notices/USN-7328-1
- https://ubuntu.com/security/notices/USN-7328-2
- https://ubuntu.com/security/notices/USN-7328-3
- https://ubuntu.com/security/notices/USN-7329-1
- https://ubuntu.com/security/notices/USN-7331-1
- https://ubuntu.com/security/notices/USN-7380-1
- https://ubuntu.com/security/notices/USN-7381-1
- https://ubuntu.com/security/notices/USN-7388-1
- https://ubuntu.com/security/notices/USN-7389-1
- https://ubuntu.com/security/notices/USN-7390-1
- https://ubuntu.com/security/notices/USN-7402-1
- https://ubuntu.com/security/notices/USN-7402-2
- https://ubuntu.com/security/notices/USN-7402-3
- https://ubuntu.com/security/notices/USN-7402-4
- https://ubuntu.com/security/notices/USN-7402-5
- https://ubuntu.com/security/notices/USN-7403-1
- https://ubuntu.com/security/notices/USN-7451-1
- https://ubuntu.com/security/notices/USN-7458-1
- https://ubuntu.com/security/notices/USN-7468-1
- https://ubuntu.com/security/notices/USN-7523-1
- https://ubuntu.com/security/notices/USN-7524-1
- https://www.cve.org/CVERecord?id=CVE-2024-56672