Re: [PATCH] ovl: fix NULL pointer dereference

[Kevin Locke <kevin@kevinlocke.name>]

On Wed, 2022-01-12 at 22:06 +0100, Christoph Fritz wrote:
>>> These have been -ENOIOCTLCMD errors but got (falsely?) converted to
>>> -ENOTTY by the recently introduced commit 5b0a414d06c3 ("ovl: fix
>>> filattr copy-up failure"):
>> 
>> Which filesystem are you using for upper (and lower) in your mount?
> 
> 
> It's tmpfs.
> 
>> Presumably the upper doesn't support file attributes, if it returns
>> -ENOIOCTLCMD?
> 
> 
> Tmpfs does support file attributes.

Although tmpfs can support extended attributes (attr(1)/xattr(7)) with
CONFIG_TMPFS_XATTR, I'm not aware of support for traditional
attributes (chattr(1)).  I'm also not able to reproduce the error
message you mentioned with extended attributes.  With your patch[^1]
applied to 5.16, I ran the following:

    mkdir lower upwork overlay
    mount -t tmpfs - lower
    mount -t tmpfs - upwork
    mkdir upwork/upper upwork/work
    touch lower/file.txt
    setfacl -m 'u:0:rwx' lower/file.txt
    mount -t overlay -o "lowerdir=$PWD/lower,upperdir=$PWD/upwork/upper,workdir=$PWD/upwork/work" - overlay
    mv overlay/file.txt overlay/file2.txt
    getfattr -d -m '.*' overlay/file2.txt

This copied file.txt from lower to upper with the
system.posix_acl_access extended attribute and did not print any
messages from overlayfs to the kernel log.

Could you provide a minimal, reproducible example for the log messages
you mentioned observing?

Thanks,
Kevin

[^1]: https://lore.kernel.org/linux-unionfs/10d8ed194b934c298713ad7f0958329b46573dd1.camel@googlemail.com/