Re: [PATCH v2 21/25] New mount API: Filter out "user="

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

On Thu, Mar 26, 2026 at 10:34:54PM +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>

Now that I've wrapped my head around the utab-only options I feel more
confident in saying

Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>

--D

> ---
>  lib/mount_fsmount.c | 15 ++++++++++++++-
>  1 file changed, 14 insertions(+), 1 deletion(-)
> 
> diff --git a/lib/mount_fsmount.c b/lib/mount_fsmount.c
> index fbe3647a8923828dba819458b815c21bbd2beaad..f42ae97faedaf2420d97e701a22725d4293e4853 100644
> --- a/lib/mount_fsmount.c
> +++ b/lib/mount_fsmount.c
> @@ -248,6 +248,16 @@ 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;
> +}
> +
>  /*
>   * Parse kernel options string and apply via fsconfig
>   * Options are comma-separated key=value pairs
> @@ -275,6 +285,7 @@ static int apply_mount_opts(int fsfd, const char *opts)
>  		 * not fsconfig().
>  		 *
>  		 * These string options (nosuid, nodev, etc.) are reconstructed
> +		 * Skip mtab-only options - they're for /run/mount/utab, not kernel
>  		 * from MS_* flags by get_mnt_flag_opts() in lib/mount.c and
>  		 * get_mnt_opts() in util/fusermount.c. Both the library path
>  		 * (via fuse_kern_mount_get_base_mnt_opts) and fusermount3 path
> @@ -282,8 +293,10 @@ static int apply_mount_opts(int fsfd, const char *opts)
>  		 * mnt_opts. They must be filtered here because they are mount
>  		 * attributes (passed to fsmount via MOUNT_ATTR_*), not
>  		 * filesystem parameters (which would be passed to fsconfig).
> +		 *
> +		 * Also skip mtab-only options - they're for /run/mount/utab, not kernel
>  		 */
> -		if (!is_mount_attr_opt(opt)) {
> +		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
> 
>