[regression 6.1.80+] "CIFS: VFS: directory entry name would overflow frame end of buf" and invisible files under certain conditions and at least with noserverino mount option

From: Salvatore Bonaccorso <carnil@debian.org>
To: regressions@lists.linux.dev, Paulo Alcantara <pc@manguebit.com>,
	Steve French <stfrench@microsoft.com>
Cc: gregkh@linuxfoundation.org, sashal@kernel.org,
	stable@vger.kernel.org, linux-cifs@vger.kernel.org
Subject: [regression 6.1.80+] "CIFS: VFS: directory entry name would overflow frame end of buf" and invisible files under certain conditions and at least with noserverino mount option
Date: Wed, 17 Apr 2024 23:44:18 +0200	[thread overview]
Message-ID: <ZiBCsoc0yf_I8In8@eldamar.lan> (raw)

Hi Paulo, hi all

In Debian we got two reports of cifs mounts not functioning, hiding
certain files. The two reports are:

https://bugs.debian.org/1069102
https://bugs.debian.org/1069092

On those cases kernel logs error

[   23.225952] CIFS: VFS: directory entry name would overflow frame end of buf 00000000a44b272c

I do not have yet a minimal reproducing setup, but I was able to
reproduce the the issue cerating a simple share (done for simplicity
with ksmbd):

[global]
	...
[poc]
        path = /srv/data
        valid users = root
        read only = no

Within /srv/data create an empty file libfoo:

# touch /srv/data/libfoo

The share is mounted with noserverino (the issue is not reproducible
without at least in my case):

mount -t cifs -o noserverino //server/poc /mnt

On each access of /mnt a new error is logged, while not showing the
libfoo file:

[   23.225952] CIFS: VFS: directory entry name would overflow frame end of buf 00000000a44b272c
[  603.494356] CIFS: VFS: directory entry name would overflow frame end of buf 000000001dbf54e1
[  633.217689] CIFS: VFS: directory entry name would overflow frame end of buf 00000000fb4597c4
[  642.791862] CIFS: VFS: directory entry name would overflow frame end of buf 0000000023b48528

I have verified that reverting in 6.1.y the commit 0947d0d463d4 ("smb:
client: set correct d_type for reparse points under DFS mounts") on
top of 6.1.87 fixes the issue.

#regzbot introduced: 0947d0d463d4

I can try to make a clean environment to reproeduce the issue, but I'm
not yet there. But the regression is related to 0947d0d463d4 ("smb:
client: set correct d_type for reparse points under DFS mounts").
The mentioned commit was as well part of 6.7.7 at least, but I'm not
able to reproduce the issue from another client running 6.7,9.

Does that ring some bell?

Regards,
Salvatore