# CVE-2022-49771: linux: In the Linux kernel, the following vulnerability has been resolved:  dm ioctl: fix misbehavior if list_versions races...

CVE-2022-49771 is fixed in linux on 1 platform, first by DEBIAN-CVE-2022-49771, released May 1, 2025. It is not reported as exploited. Patch Radar priority: Routine.

- Web page: https://patchblox.com/security/cve/CVE-2022-49771
- Priority: Routine
- CVSS: 4.7 (medium)
- EPSS: 0.0016
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: May 1, 2025

## Description

In the Linux kernel, the following vulnerability has been resolved:  dm ioctl: fix misbehavior if list_versions races with module loading  __list_versions will first estimate the required space using the "dm_target_iterate(list_version_get_needed, &needed)" call and then will fill the space using the "dm_target_iterate(list_version_get_info, &iter_info)" call. Each of these calls locks the targets using the "down_read(&_lock)" and "up_read(&_lock)" calls, however between the first and second "dm_target_iterate" there is no lock held and the target modules can be loaded at this point, so the second "dm_target_iterate" call may need more space than what was the first "dm_target_iterate" returned.  The code tries to handle this overflow (see the beginning of list_version_get_info), however this handling is incorrect.  The code sets "param->data_size = param->data_start + needed" and "iter_info.end = (char *)vers+len" - "needed" is the size returned by the first dm_target_iterate call; "len" is the size of the buffer allocated by userspace.  "len" may be greater than "needed"; in this case, the code will write up to "len" bytes into the buffer, however param->data_size is set to "needed", so it may write data past the param->data_size value. The ioctl interface copies only up to param->data_size into userspace, thus part of the result will be truncated.  Fix this bug by setting "iter_info.end = (char *)vers + needed;" - this guarantees that the second "dm_target_iterate" call will write only up to the "needed" buffer and it will exit with "DM_BUFFER_FULL_FLAG" if it overflows the "needed" space - in this case, userspace will allocate a larger buffer and retry.  Note that there is also a bug in list_version_get_needed - we need to add "strlen(tt->name) + 1" to the needed size, not "strlen(tt->name)".

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | linux Debian 12.15 (bookworm) | 6.0.10-1 | [DEBIAN-CVE-2022-49771](https://patchblox.com/security/data/fix/linux/debian-cve-2022-49771.md) | May 1, 2025 |
| Linux | linux Debian 13.5 (trixie) | 6.0.10-1 | [DEBIAN-CVE-2022-49771](https://patchblox.com/security/data/fix/linux/debian-cve-2022-49771.md) | May 1, 2025 |
| Linux | linux Debian 14 | 6.0.10-1 | [DEBIAN-CVE-2022-49771](https://patchblox.com/security/data/fix/linux/debian-cve-2022-49771.md) | May 1, 2025 |

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