linux-kernel - Re: [PATCH] fs: don't call posix_acl_listxattr in generic

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Date:   Tue, 05 Sep 2023 06:50:49 -0400
From:   Jeff Layton <jlayton@...nel.org>
To:     Ondrej Valousek <ondrej.valousek.xm@...esas.com>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Christian Brauner <brauner@...nel.org>
Cc:     "trondmy@...merspace.com" <trondmy@...merspace.com>,
        "eggert@...ucla.edu" <eggert@...ucla.edu>,
        "bruno@...sp.org" <bruno@...sp.org>,
        "linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] fs: don't call posix_acl_listxattr in generic_listxattr

On Mon, 2023-09-04 at 20:36 +0000, Ondrej Valousek wrote:
> Hi Jeff,
> 
> I can confirm that with rawhide kernel 6.5 the error is gone, i.e.
> 
> Listxattr() shows only "system.nfs4_acl" attribute on NFSv4 filesystem,
> 
> Problem is, that (on the same kernel) getxattr(name,XATTR_NAME_POSIX_ACL_ACCESS, 0,0)
> Sets errno to ENODATA where "name" is file on NFSv4.
> 
> This is different behavior to the previous versions, i.e. on RHEL8 getxattr() sets errno to ENOTSUP in the same scenario - which is what I'd expect more.
> 
> Is the change of the getxattr() behavior expected or not?
> 
> Thanks,
> Ondrej
> 

I'd say not. I've been working through xfstests failures on NFS and
didn't realize that this was a regression, and posted this fstests patch
recently:

    https://lore.kernel.org/fstests/20230830-fixes-v4-1-88d7b8572aa3@kernel.org/

It would be nice if getxattr were also fixed here.

Cheers,
Jeff

> -----Original Message-----
> From: Jeff Layton <jlayton@...nel.org> 
> Sent: Dienstag, 16. Mai 2023 14:47
> To: Alexander Viro <viro@...iv.linux.org.uk>; Christian Brauner <brauner@...nel.org>
> Cc: trondmy@...merspace.com; eggert@...ucla.edu; bruno@...sp.org; Ondrej Valousek <ondrej.valousek.xm@...esas.com>; linux-fsdevel@...r.kernel.org; linux-kernel@...r.kernel.org
> Subject: [PATCH] fs: don't call posix_acl_listxattr in generic_listxattr
> 
> Commit f2620f166e2a caused the kernel to start emitting POSIX ACL xattrs for NFSv4 inodes, which it doesn't support. The only other user of generic_listxattr is HFS (classic) and it doesn't support POSIX ACLs either.
> 
> Fixes: f2620f166e2a xattr: simplify listxattr helpers
> Reported-by: Ondrej Valousek <ondrej.valousek.xm@...esas.com>
> Signed-off-by: Jeff Layton <jlayton@...nel.org>
> ---
>  fs/xattr.c | 15 +++++++++------
>  1 file changed, 9 insertions(+), 6 deletions(-)
> 
> diff --git a/fs/xattr.c b/fs/xattr.c
> index fcf67d80d7f9..e7bbb7f57557 100644
> --- a/fs/xattr.c
> +++ b/fs/xattr.c
> @@ -985,9 +985,16 @@ int xattr_list_one(char **buffer, ssize_t *remaining_size, const char *name)
>  	return 0;
>  }
>  
> -/*
> +/**
> + * generic_listxattr - run through a dentry's xattr list() operations
> + * @dentry: dentry to list the xattrs
> + * @buffer: result buffer
> + * @buffer_size: size of @buffer
> + *
>   * Combine the results of the list() operation from every xattr_handler in the
> - * list.
> + * xattr_handler stack.
> + *
> + * Note that this will not include the entries for POSIX ACLs.
>   */
>  ssize_t
>  generic_listxattr(struct dentry *dentry, char *buffer, size_t buffer_size) @@ -996,10 +1003,6 @@ generic_listxattr(struct dentry *dentry, char *buffer, size_t buffer_size)
>  	ssize_t remaining_size = buffer_size;
>  	int err = 0;
>  
> -	err = posix_acl_listxattr(d_inode(dentry), &buffer, &remaining_size);
> -	if (err)
> -		return err;
> -
>  	for_each_xattr_handler(handlers, handler) {
>  		if (!handler->name || (handler->list && !handler->list(dentry)))
>  			continue;
> --
> 2.40.1
> 

-- 
Jeff Layton <jlayton@...nel.org>