# CVE-2022-48733: linux: In the Linux kernel, the following vulnerability has been resolved:  btrfs: fix use-after-free after failure to creat...

CVE-2022-48733 is fixed in linux on 1 platform, first by DEBIAN-CVE-2022-48733, released June 20, 2024. It is not reported as exploited. Patch Radar priority: High.

- Web page: https://patchblox.com/security/cve/CVE-2022-48733
- Priority: High
- CVSS: 7.8 (high)
- EPSS: 0.0023
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Jun 20, 2024

## Description

In the Linux kernel, the following vulnerability has been resolved:  btrfs: fix use-after-free after failure to create a snapshot  At ioctl.c:create_snapshot(), we allocate a pending snapshot structure and then attach it to the transaction's list of pending snapshots. After that we call btrfs_commit_transaction(), and if that returns an error we jump to 'fail' label, where we kfree() the pending snapshot structure. This can result in a later use-after-free of the pending snapshot:  1) We allocated the pending snapshot and added it to the transaction's    list of pending snapshots;  2) We call btrfs_commit_transaction(), and it fails either at the first    call to btrfs_run_delayed_refs() or btrfs_start_dirty_block_groups().    In both cases, we don't abort the transaction and we release our    transaction handle. We jump to the 'fail' label and free the pending    snapshot structure. We return with the pending snapshot still in the    transaction's list;  3) Another task commits the transaction. This time there's no error at    all, and then during the transaction commit it accesses a pointer    to the pending snapshot structure that the snapshot creation task    has already freed, resulting in a user-after-free.  This issue could actually be detected by smatch, which produced the following warning:    fs/btrfs/ioctl.c:843 create_snapshot() warn: '&pending_snapshot->list' not removed from list  So fix this by not having the snapshot creation ioctl directly add the pending snapshot to the transaction's list. Instead add the pending snapshot to the transaction handle, and then at btrfs_commit_transaction() we add the snapshot to the list only when we can guarantee that any error returned after that point will result in a transaction abort, in which case the ioctl code can safely free the pending snapshot and no one can access it anymore.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | linux Debian 12.15 (bookworm) | 5.16.10-1 | [DEBIAN-CVE-2022-48733](https://patchblox.com/security/data/fix/linux/debian-cve-2022-48733.md) | Jun 20, 2024 |
| Linux | linux Debian 13.5 (trixie) | 5.16.10-1 | [DEBIAN-CVE-2022-48733](https://patchblox.com/security/data/fix/linux/debian-cve-2022-48733.md) | Jun 20, 2024 |
| Linux | linux Debian 14 | 5.16.10-1 | [DEBIAN-CVE-2022-48733](https://patchblox.com/security/data/fix/linux/debian-cve-2022-48733.md) | Jun 20, 2024 |

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