Re: [PATCH 18/19] New mount API: Filter out "user="

["Darrick J. Wong" <djwong@kernel.org>]

On Mon, Mar 23, 2026 at 06:45:13PM +0100, Bernd Schubert wrote:
> From: Bernd Schubert <bschubert@ddn.com>
> 
> This gets added in the fusermount process and kernel then fails
> the mount.
> 
> Signed-off-by: Bernd Schubert <bschubert@ddn.com>
> ---
>  lib/mount_fsmount.c | 13 ++++++++++++-
>  1 file changed, 12 insertions(+), 1 deletion(-)
> 
> diff --git a/lib/mount_fsmount.c b/lib/mount_fsmount.c
> index f1fec790bb80f8815d485a068dc7efdff1746309..76c14cf9a22465160fc6b206ca9b6c9e7300adba 100644
> --- a/lib/mount_fsmount.c
> +++ b/lib/mount_fsmount.c
> @@ -218,6 +218,16 @@ static int is_mount_attr_opt(const char *opt)
>  	       strcmp(opt, "symfollow") == 0;
>  }
>  
> +/**
> + * Check if an option is a mount table option (not passed to fsconfig)
> + */
> +static int is_mtab_only_opt(const char *opt)
> +{
> +	/* These options are for /run/mount/utab only, not for the kernel */
> +	return strncmp(opt, "user=", 5) == 0 ||
> +	       strcmp(opt, "rw") == 0;

Oh, so these are added to the mount options string by get_mnt_opts
and now they need to be pulled out so they aren't passed to fsconfig?
How'd they get into the argument list in the first place?

--D

> +}
> +
>  /*
>   * Parse kernel options string and apply via fsconfig
>   * Options are comma-separated key=value pairs
> @@ -241,7 +251,8 @@ static int apply_mount_opts(int fsfd, const char *opts)
>  	opt = strtok_r(opts_copy, ",", &saveptr);
>  	while (opt) {
>  		/* Skip mount attributes - they're handled by fsmount(), not fsconfig() */
> -		if (!is_mount_attr_opt(opt)) {
> +		/* Skip mtab-only options - they're for /run/mount/utab, not kernel */
> +		if (!is_mount_attr_opt(opt) && !is_mtab_only_opt(opt)) {
>  			res = apply_opt_key_value(fsfd, opt);
>  			if (res < 0) {
>  				free(opts_copy);
> 
> -- 
> 2.43.0
> 
>