Re: [PATCH v2 2/4] ceph: validate cluster FSID for new device syntax

[Luis Henriques <lhenriques@suse.de>]

On Fri, Jul 02, 2021 at 12:18:19PM +0530, Venky Shankar wrote:
> The new device syntax requires the cluster FSID as part
> of the device string. Use this FSID to verify if it matches
> the cluster FSID we get back from the monitor, failing the
> mount on mismatch.
> 
> Also, rename parse_fsid() to ceph_parse_fsid() as it is too
> generic.
> 
> Signed-off-by: Venky Shankar <vshankar@redhat.com>
> ---
>  fs/ceph/super.c              | 9 +++++++++
>  fs/ceph/super.h              | 1 +
>  include/linux/ceph/libceph.h | 1 +
>  net/ceph/ceph_common.c       | 5 +++--
>  4 files changed, 14 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/ceph/super.c b/fs/ceph/super.c
> index 0b324e43c9f4..03e5f4bb2b6f 100644
> --- a/fs/ceph/super.c
> +++ b/fs/ceph/super.c
> @@ -268,6 +268,9 @@ static int ceph_parse_new_source(const char *dev_name, const char *dev_name_end,
>  	if (!fs_name_start)
>  		return invalfc(fc, "missing file system name");
>  
> +	if (ceph_parse_fsid(fsid_start, &fsopt->fsid))
> +		return invalfc(fc, "invalid fsid format");
> +
>  	++fs_name_start; /* start of file system name */
>  	fsopt->mds_namespace = kstrndup(fs_name_start,
>  					dev_name_end - fs_name_start, GFP_KERNEL);
> @@ -750,6 +753,12 @@ static struct ceph_fs_client *create_fs_client(struct ceph_mount_options *fsopt,
>  	}
>  	opt = NULL; /* fsc->client now owns this */
>  
> +	/* help learn fsid */
> +	if (fsopt->new_dev_syntax) {
> +		ceph_check_fsid(fsc->client, &fsopt->fsid);

This call to ceph_check_fsid() made me wonder what would happen if I use
the wrong fsid with the new syntax.  And the result is:

[   41.882334] libceph: mon0 (1)192.168.155.1:40594 session established
[   41.884537] libceph: bad fsid, had d52783e6-efc2-4dce-ad01-aa3272fa5f66 got 90bdb539-9d95-402e-8f23-b0e26cba8b1b
[   41.885955] libceph: bad fsid, had d52783e6-efc2-4dce-ad01-aa3272fa5f66 got 90bdb539-9d95-402e-8f23-b0e26cba8b1b
[   41.889313] libceph: bad fsid, had d52783e6-efc2-4dce-ad01-aa3272fa5f66 got 90bdb539-9d95-402e-8f23-b0e26cba8b1b
[   41.892578] libceph: osdc handle_map corrupt msg

... followed by a msg dump.

I guess this means that manually setting the fsid requires changes to the
messenger (I've only tested with v1) so that it gracefully handles this
scenario.

Cheers,
--
Luís

> +		fsc->client->have_fsid = true;
> +	}
> +
>  	fsc->client->extra_mon_dispatch = extra_mon_dispatch;
>  	ceph_set_opt(fsc->client, ABORT_ON_FULL);
>  
> diff --git a/fs/ceph/super.h b/fs/ceph/super.h
> index 8f71184b7c85..ce5fb90a01a4 100644
> --- a/fs/ceph/super.h
> +++ b/fs/ceph/super.h
> @@ -99,6 +99,7 @@ struct ceph_mount_options {
>  	char *server_path;    /* default NULL (means "/") */
>  	char *fscache_uniq;   /* default NULL */
>  	char *mon_addr;
> +	struct ceph_fsid fsid;
>  };
>  
>  struct ceph_fs_client {
> diff --git a/include/linux/ceph/libceph.h b/include/linux/ceph/libceph.h
> index 409d8c29bc4f..75d059b79d90 100644
> --- a/include/linux/ceph/libceph.h
> +++ b/include/linux/ceph/libceph.h
> @@ -296,6 +296,7 @@ extern bool libceph_compatible(void *data);
>  extern const char *ceph_msg_type_name(int type);
>  extern int ceph_check_fsid(struct ceph_client *client, struct ceph_fsid *fsid);
>  extern void *ceph_kvmalloc(size_t size, gfp_t flags);
> +extern int ceph_parse_fsid(const char *str, struct ceph_fsid *fsid);
>  
>  struct fs_parameter;
>  struct fc_log;
> diff --git a/net/ceph/ceph_common.c b/net/ceph/ceph_common.c
> index 97d6ea763e32..da480757fcca 100644
> --- a/net/ceph/ceph_common.c
> +++ b/net/ceph/ceph_common.c
> @@ -217,7 +217,7 @@ void *ceph_kvmalloc(size_t size, gfp_t flags)
>  	return p;
>  }
>  
> -static int parse_fsid(const char *str, struct ceph_fsid *fsid)
> +int ceph_parse_fsid(const char *str, struct ceph_fsid *fsid)
>  {
>  	int i = 0;
>  	char tmp[3];
> @@ -247,6 +247,7 @@ static int parse_fsid(const char *str, struct ceph_fsid *fsid)
>  	dout("parse_fsid ret %d got fsid %pU\n", err, fsid);
>  	return err;
>  }
> +EXPORT_SYMBOL(ceph_parse_fsid);
>  
>  /*
>   * ceph options
> @@ -465,7 +466,7 @@ int ceph_parse_param(struct fs_parameter *param, struct ceph_options *opt,
>  		break;
>  
>  	case Opt_fsid:
> -		err = parse_fsid(param->string, &opt->fsid);
> +		err = ceph_parse_fsid(param->string, &opt->fsid);
>  		if (err) {
>  			error_plog(&log, "Failed to parse fsid: %d", err);
>  			return err;
> -- 
> 2.27.0
>