# CVE-2023-52909: linux: In the Linux kernel, the following vulnerability has been resolved:  nfsd: fix handling of cached open files in nfsd4...

CVE-2023-52909 is fixed in linux on 1 platform, first by DEBIAN-CVE-2023-52909, released August 21, 2024. It is not reported as exploited. Patch Radar priority: Routine.

- Web page: https://patchblox.com/security/cve/CVE-2023-52909
- Priority: Routine
- CVSS: 4.7 (medium)
- EPSS: 0.0064
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Aug 21, 2024

## Description

In the Linux kernel, the following vulnerability has been resolved:  nfsd: fix handling of cached open files in nfsd4_open codepath  Commit fb70bf124b05 ("NFSD: Instantiate a struct file when creating a regular NFSv4 file") added the ability to cache an open fd over a compound. There are a couple of problems with the way this currently works:  It's racy, as a newly-created nfsd_file can end up with its PENDING bit cleared while the nf is hashed, and the nf_file pointer is still zeroed out. Other tasks can find it in this state and they expect to see a valid nf_file, and can oops if nf_file is NULL.  Also, there is no guarantee that we'll end up creating a new nfsd_file if one is already in the hash. If an extant entry is in the hash with a valid nf_file, nfs4_get_vfs_file will clobber its nf_file pointer with the value of op_file and the old nf_file will leak.  Fix both issues by making a new nfsd_file_acquirei_opened variant that takes an optional file pointer. If one is present when this is called, we'll take a new reference to it instead of trying to open the file. If the nfsd_file already has a valid nf_file, we'll just ignore the optional file and pass the nfsd_file back as-is.  Also rework the tracepoints a bit to allow for an "opened" variant and don't try to avoid counting acquisitions in the case where we already have a cached open file.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | linux Debian 12.15 (bookworm) | 6.1.7-1 | [DEBIAN-CVE-2023-52909](https://patchblox.com/security/data/fix/linux/debian-cve-2023-52909.md) | Aug 21, 2024 |
| Linux | linux Debian 13.5 (trixie) | 6.1.7-1 | [DEBIAN-CVE-2023-52909](https://patchblox.com/security/data/fix/linux/debian-cve-2023-52909.md) | Aug 21, 2024 |
| Linux | linux Debian 14 | 6.1.7-1 | [DEBIAN-CVE-2023-52909](https://patchblox.com/security/data/fix/linux/debian-cve-2023-52909.md) | Aug 21, 2024 |

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