# CVE-2023-52609: linux: In the Linux kernel, the following vulnerability has been resolved:  binder: fix race between mmput() and do_exit()...

CVE-2023-52609 is fixed in linux on 1 platform, first by DEBIAN-CVE-2023-52609, released March 18, 2024. It is not reported as exploited. Patch Radar priority: Routine.

- Web page: https://patchblox.com/security/cve/CVE-2023-52609
- Priority: Routine
- CVSS: 4.7 (medium)
- EPSS: 0.0019
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Mar 18, 2024

## Description

In the Linux kernel, the following vulnerability has been resolved:  binder: fix race between mmput() and do_exit()  Task A calls binder_update_page_range() to allocate and insert pages on a remote address space from Task B. For this, Task A pins the remote mm via mmget_not_zero() first. This can race with Task B do_exit() and the final mmput() refcount decrement will come from Task A.    Task A            | Task B   ------------------+------------------   mmget_not_zero()  |                     |  do_exit()                     |    exit_mm()                     |      mmput()   mmput()           |     exit_mmap()     |       remove_vma()  |         fput()      |  In this case, the work of ____fput() from Task B is queued up in Task A as TWA_RESUME. So in theory, Task A returns to userspace and the cleanup work gets executed. However, Task A instead sleep, waiting for a reply from Task B that never comes (it's dead).  This means the binder_deferred_release() is blocked until an unrelated binder event forces Task A to go back to userspace. All the associated death notifications will also be delayed until then.  In order to fix this use mmput_async() that will schedule the work in the corresponding mm->async_put_work WQ instead of Task A.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | linux Debian 12.15 (bookworm) | 6.1.76-1 | [DEBIAN-CVE-2023-52609](https://patchblox.com/security/data/fix/linux/debian-cve-2023-52609.md) | Mar 18, 2024 |
| Linux | linux Debian 13.5 (trixie) | 6.6.15-1 | [DEBIAN-CVE-2023-52609](https://patchblox.com/security/data/fix/linux/debian-cve-2023-52609.md) | Mar 18, 2024 |
| Linux | linux Debian 14 | 6.6.15-1 | [DEBIAN-CVE-2023-52609](https://patchblox.com/security/data/fix/linux/debian-cve-2023-52609.md) | Mar 18, 2024 |

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