From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: linux-cve-announce@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@kernel.org>
Subject: CVE-2026-89677: nfsd: fix possible fh_compose of wrong dentry in nfsd4_create_file()
Date: Fri, 11 Sep 2026 21:46:06 +0200 [thread overview]
Message-ID: <2026091150-CVE-2026-89677-6379@gregkh> (raw)
From: Greg Kroah-Hartman <gregkh@kernel.org>
Description
===========
In the Linux kernel, the following vulnerability has been resolved:
nfsd: fix possible fh_compose of wrong dentry in nfsd4_create_file()
dentry_create() can hypothetically provide a different dentry than the
one passed in. This could happen, for example, if the exported
filesystem is NFS, and the server returned to OPEN a filehandle which
matched a directory that was already in the dcache. Clearly this would
not be expected!
If this were to happen the dentry (child) that was already stored in
resfhp could be freed and later dereferenced.
We shouldn't call fh_compose() until we are certain that we have the
final dentry, so this patch moved the fh_compose() call to two places:
one for the case where the target already exists, and one after
dentry_create() where it was created.
The Linux kernel CVE team has assigned CVE-2026-89677 to this issue.
Affected and fixed versions
===========================
Issue introduced in 7.0 with commit 64a989dbd144e0622371396461b11335459692d2 and fixed in 7.2.4 with commit 033e783709ce99662cf81f6abcad746a8da9d35f
Issue introduced in 7.0 with commit 64a989dbd144e0622371396461b11335459692d2 and fixed in 7.3-rc1 with commit 3e2c79360c6a89975ec5b5a7d4ef937e4db91a27
Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.
Unaffected versions might change over time as fixes are backported to
older supported kernel versions. The official CVE entry at
https://cve.org/CVERecord/?id=CVE-2026-89677
will be updated if fixes are backported, please check that for the most
up to date information about this issue.
Affected files
==============
The file(s) affected by this issue are:
fs/nfsd/nfs4proc.c
Mitigation
==========
The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes. Individual
changes are never tested alone, but rather are part of a larger kernel
release. Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all. If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
https://git.kernel.org/stable/c/033e783709ce99662cf81f6abcad746a8da9d35f
https://git.kernel.org/stable/c/3e2c79360c6a89975ec5b5a7d4ef937e4db91a27
reply other threads:[~2026-09-11 20:02 UTC|newest]
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