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From: Thorsten Leemhuis <regressions@leemhuis.info>
Newsgroups: linux.debian.bugs.dist,linux.debian.kernel
Subject: Bug#1128861: Regression: Missing check in nfsd_permission() causes -ENOLCK No locks available
Date: Fri, 27 Feb 2026 11:10:01 +0100
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[CCing a few people and lists]

On 2/24/26 03:09, Tj wrote:
> Upstream commit 4cc9b9f2bf4dfe13fe573 "nfsd: refine and rename 
> NFSD_MAY_LOCK" and
>   stable v6.12.54 commit 18744bc56b0ec

In case anyone just like me is wondering: the latter is a backport of
the former.

>  (re)moves checks from  fs/nfsd/vfs.c::nfsd_permission().>   This causes NFS clients to see
> 
> $ flock -e -w 4 /srv/NAS/test/debian-13.3.0-amd64-netinst.iso sleep 1
> flock: /srv/NAS/test/debian-13.3.0-amd64-netinst.iso: No locks available

Does this happen on mainline (e.g. 7.0-rc1) as well?

Ciao, Thorsten

> Keeping the check in nfsd_permission() whilst also copying it to 
> fs/nfsd/nfsfh.c::__fh_verify() resolves the issue.
> 
> This was discovered on the Debian openQA infrastructure server when 
> upgrading kernel from v6.12.48 to later v6.12.y where worker hosts (with 
> any earlier or later kernel version) pass NFSv3 mounted ISO images to 
> qemu-system-x86_64 and it reports:
> 
> !!! : qemu-system-x86_64: -device 
> scsi-cd,id=cd0-device,drive=cd0-overlay0,serial=cd0: Failed to get 
> "consistent read" lock: No locks available
> QEMU: Is another process using the image 
> [/var/lib/openqa/pool/2/20260223-1-debian-testing-amd64-netinst.iso]?
> 
> A simple reproducer with the server using:
> 
> # cat /etc/exports.d/test.exports
> /srv/NAS/test 
> fdff::/64(fsid=0,rw,no_root_squash,sync,no_subtree_check,auth_nlm)
> 
> and clients using:
> 
> # mount -t nfs [fdff::2]:/srv/NAS/test /srv/NAS/test -o 
> proto=tcp6,ro,fsc,soft
> 
> will trigger the error as shown above:
> 
> $ flock -e -w 4 /srv/NAS/test/debian-13.3.0-amd64-netinst.iso sleep 1
> flock: /srv/NAS/test/debian-13.3.0-amd64-netinst.iso: No locks available
> 
> A simple test program calling fcntl() with the same arguments QEMU uses 
> also fails in the same way.
> 
> $ ./nfs3_range_lock_test 
> /srv/NAS/test/debian-13.3.0-amd64-netinst.{iso,overlay}
> Opened base file: /srv/NAS/test/debian-13.3.0-amd64-netinst.iso
> Opened overlay file: /srv/NAS/test/debian-13.3.0-amd64-netinst.overlay
> Attempting lock at 4 on /srv/NAS/test/debian-13.3.0-amd64-netinst.iso
> fcntl(fd, F_GETLK, &fl) failed on base: No locks available
> Attempting lock at 8 on /srv/NAS/test/debian-13.3.0-amd64-netinst.overlay
> fcntl(fd, F_GETLK, &fl) failed on overlay: No locks available
> 
>