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18 lines
2.2 KiB
Markdown
18 lines
2.2 KiB
Markdown
### [CVE-2024-56672](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2024-56672)
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### Description
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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. Towalk up, it uses blkcg_parent(blkcg) but it was calling that afterblkcg_destroy_blkgs(blkcg) which could free the blkcg, leading to thefollowing 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/0x30Note that the UAF is not easy to trigger as the free path is indirectedbehind a couple RCU grace periods and a work item execution. I could onlytrigger it with artifical msleep() injected in blkcg_unpin_online().Fix it by reading the parent pointer before destroying the blkcg's blkg's.
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### POC
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#### Reference
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No PoCs from references.
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#### Github
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- https://github.com/cku-heise/euvd-api-doc
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