In the Linux kernel, the following vulnerability has been resolved:

nfs: fix UAF in direct writes

In production we have been hitting the following warning consistently

------------[ cut here ]------------
refcount_t: underflow; use-after-free.
WARNING: CPU: 17 PID: 1800359 at lib/refcount.c:28 refcount_warn_saturate+0x9c/0xe0
Workqueue: nfsiod nfs_direct_write_schedule_work [nfs]
RIP: 0010:refcount_warn_saturate+0x9c/0xe0
PKRU: 55555554
Call Trace:
<TASK>
? __warn+0x9f/0x130
? refcount_warn_saturate+0x9c/0xe0
? report_bug+0xcc/0x150
? handle_bug+0x3d/0x70
? exc_invalid_op+0x16/0x40
? asm_exc_invalid_op+0x16/0x20
? refcount_warn_saturate+0x9c/0xe0
nfs_direct_write_schedule_work+0x237/0x250 [nfs]
process_one_work+0x12f/0x4a0
worker_thread+0x14e/0x3b0
? ZSTD_getCParams_internal+0x220/0x220
kthread+0xdc/0x120
? __btf_name_valid+0xa0/0xa0
ret_from_fork+0x1f/0x30

This is because we're completing the nfs_direct_request twice in a row.

The source of this is when we have our commit requests to submit, we
process them and send them off, and then in the completion path for the
commit requests we have

if (nfs_commit_end(cinfo.mds))
nfs_direct_write_complete(dreq);

However since we're submitting asynchronous requests we sometimes have
one that completes before we submit the next one, so we end up calling
complete on the nfs_direct_request twice.

The only other place we use nfs_generic_commit_list() is in
__nfs_commit_inode, which wraps this call in a

nfs_commit_begin();
nfs_commit_end();

Which is a common pattern for this style of completion handling, one
that is also repeated in the direct code with get_dreq()/put_dreq()
calls around where we process events as well as in the completion paths.

Fix this by using the same pattern for the commit requests.

Before with my 200 node rocksdb stress running this warning would pop
every 10ish minutes. With my patch the stress test has been running for
several hours without popping.
History

Thu, 28 Aug 2025 14:45:00 +0000


Mon, 23 Dec 2024 13:45:00 +0000

Type Values Removed Values Added
First Time appeared Debian
Debian debian Linux
Linux
Linux linux Kernel
Weaknesses CWE-416
CPEs cpe:2.3:o:debian:debian_linux:10.0:*:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
Vendors & Products Debian
Debian debian Linux
Linux
Linux linux Kernel
Metrics cvssV3_1

{'score': 5.5, 'vector': 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H'}

cvssV3_1

{'score': 7.8, 'vector': 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H'}


Fri, 22 Nov 2024 12:00:00 +0000

Type Values Removed Values Added
References

Wed, 13 Nov 2024 02:45:00 +0000

Type Values Removed Values Added
CPEs cpe:/a:redhat:enterprise_linux:9
cpe:/o:redhat:enterprise_linux:9

Tue, 05 Nov 2024 10:45:00 +0000

Type Values Removed Values Added
References

Thu, 08 Aug 2024 19:15:00 +0000

Type Values Removed Values Added
First Time appeared Redhat
Redhat enterprise Linux
CPEs cpe:/a:redhat:enterprise_linux:8::nfv
cpe:/o:redhat:enterprise_linux:8
Vendors & Products Redhat
Redhat enterprise Linux

cve-icon MITRE

Status: PUBLISHED

Assigner: Linux

Published:

Updated: 2025-08-28T14:42:40.717Z

Reserved: 2024-02-19T14:20:24.200Z

Link: CVE-2024-26958

cve-icon Vulnrichment

Updated: 2024-08-02T00:21:05.688Z

cve-icon NVD

Status : Modified

Published: 2024-05-01T06:15:12.090

Modified: 2025-08-28T15:15:41.310

Link: CVE-2024-26958

cve-icon Redhat

Severity : Moderate

Publid Date: 2024-05-01T00:00:00Z

Links: CVE-2024-26958 - Bugzilla

cve-icon OpenCVE Enrichment

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