`davfs2 1.7.1` fails silently on kernel `6.18.29+rpt-rpi-2712` (Raspberry Pi 5) — fixed by upgrading to `1.7.2`

[jpasquier]

Describe the bug

After a routine kernel update from 6.12.75 to 6.18.29, davfs2 stopped working silently. The mount command returns no error, but accessing the mount point fails with:

/mnt/kDrive: Invalid argument (os error 22)

The issue was reproduced with two different WebDAV servers, ruling out a server-specific problem.

Workaround

Either:

• Boot the previous kernel (6.12.75+rpt-rpi-2712) via config.txt
• Or upgrade davfs2 to 1.7.2 from Debian 14:

wget http://ftp.debian.org/debian/pool/main/d/davfs2/davfs2_1.7.2-3_arm64.deb
sudo dpkg -i davfs2_1.7.2-1_arm64.deb

Conclusion

The combination of kernel 6.18.29 + davfs2 1.7.1 is broken. It is unclear whether the kernel introduced a regression or exposed a pre-existing bug fixed in davfs2 1.7.2.

Steps to reproduce the behaviour

1. Run Raspberry Pi OS with kernel 6.18.29+rpt-rpi-2712
2. Install davfs2 1.7.1 (default in current RPi OS repos)
3. Run sudo mount -t davfs <webdav-url> /mnt/<mountpoint>
4. Try to access the mount point → Invalid argument (os error 22)

Device (s)

Raspberry Pi 5

System

Environment

• Hardware: Raspberry Pi 5
• OS: Raspberry Pi OS (64-bit)
• Kernel (broken): 6.18.29+rpt-rpi-2712
• Kernel (working): 6.12.75+rpt-rpi-2712
• davfs2 (broken): 1.7.1
• davfs2 (working): 1.7.2 (from Debian 14/forky)

cat /etc/rpi-issue
Raspberry Pi reference 2025-10-01
Generated using pi-gen, https://github.com/RPi-Distro/pi-gen, 7dadcf1fc5ce1648ab09409ab978831690c9a955, stage4

vcgencmd version
2025/05/08 15:13:17 
Copyright (c) 2012 Broadcom
version 69471177 (release) (embedded)

uname -a
Linux pi5 6.18.29+rpt-rpi-2712 #1 SMP PREEMPT Debian 1:6.18.29-1+rpt1 (2026-05-12) aarch64 GNU/Linux

Logs

No response

Additional context

No response

[popcornmix]

I found this bug report

1.7.2 fixes this. It's likely because of this item in the changelog:
Increase buf read size to 64 (fixes read issue on linux 6.16)
Try increasing the buf size to 64 in your davfs2.conf file.

Can you test that workaround of 1.7.1 with increased buf size?
If it fixes it we can likely update the package in trixie.

[jpasquier]

I downgraded to 1.7.1, and increased the buf size to 64. It fixes the issue.

[popcornmix]

@XECDesign might be worth considering one of:
adjust bufsize to 64 in davfs2.conf
cherry-pick the commit "increase buf read size to 64"
bump to 1.7.2

[XECDesign]

cherry-pick the commit "increase buf read size to 64"

Done