[Cluster-devel] [PATCH RHEL6] libgfs2: Use a matching context mount option in mount_gfs2_meta

[Bob Peterson <rpeterso@redhat.com>]

----- Original Message -----
> On a system with SELinux enabled, if a gfs2 file system is mounted with
> a context= option, the tools gfs2_quota, gfs2_tool, gfs2_grow and
> gfs2_jadd will fail with "Device or resource busy". This is due to
> SELinux failing the mount due to a mismatched context ("SELinux: mount
> invalid.  Same superblock, different security settings").
> 
> In order to work around this, parse the context option of the gfs2 mount
> point in is_pathname_mounted() and use it in mount_gfs2_meta().
> 
> Resolves: rhbz#1121693
> 
> Signed-off-by: Andrew Price <anprice@redhat.com>
> ---
>  gfs2/libgfs2/libgfs2.h |  1 +
>  gfs2/libgfs2/misc.c    | 21 ++++++++++++++++++++-
>  2 files changed, 21 insertions(+), 1 deletion(-)
> 
> diff --git a/gfs2/libgfs2/libgfs2.h b/gfs2/libgfs2/libgfs2.h
> index 9c20f11..25286d1 100644
> --- a/gfs2/libgfs2/libgfs2.h
> +++ b/gfs2/libgfs2/libgfs2.h
> @@ -217,6 +217,7 @@ struct gfs2_sbd {
>  
>  	int device_fd;
>  	int path_fd;
> +	char *secontext;
>  
>  	uint64_t sb_addr;
>  
> diff --git a/gfs2/libgfs2/misc.c b/gfs2/libgfs2/misc.c
> index 8e0ca6f..5ef4a2a 100644
> --- a/gfs2/libgfs2/misc.c
> +++ b/gfs2/libgfs2/misc.c
> @@ -100,6 +100,24 @@ int compute_constants(struct gfs2_sbd *sdp)
>  	return 0;
>  }
>  
> +/**
> + * Returns a duplicate of the 'context' mount option, or NULL if not found.
> + */
> +static char *copy_context_opt(struct mntent *mnt)
> +{
> +	char *ctx, *end;
> +
> +	ctx = hasmntopt(mnt, "context");
> +	if (ctx == NULL)
> +		return NULL;
> +
> +	end = strchr(ctx, ',');
> +	if (end == NULL)
> +		return NULL;
> +
> +	return strndup(ctx, end - ctx);
> +}
> +
>  int is_pathname_mounted(struct gfs2_sbd *sdp, int *ro_mount)
>  {
>  	FILE *fp;
> @@ -161,6 +179,7 @@ int is_pathname_mounted(struct gfs2_sbd *sdp, int
> *ro_mount)
>  		return 0;
>  	if (hasmntopt(mnt, MNTOPT_RO))
>                 *ro_mount = 1;
> +	sdp->secontext = copy_context_opt(mnt);
>  	return 1; /* mounted */
>  }
>  
> @@ -319,7 +338,7 @@ int mount_gfs2_meta(struct gfs2_sbd *sdp)
>  	sigaction(SIGCONT, &sa, NULL);
>  	sigaction(SIGUSR1, &sa, NULL);
>  	sigaction(SIGUSR2, &sa, NULL);
> -	ret = mount(sdp->path_name, sdp->metafs_path, "gfs2meta", 0, NULL);
> +	ret = mount(sdp->path_name, sdp->metafs_path, "gfs2meta", 0,
> sdp->secontext);
>  	if (ret) {
>  		rmdir(sdp->metafs_path);
>  		return -1;
> --
> 1.9.3
> 
> 
Hi,

Is this a memory leak (albeit a small one) or did I miss something?
I don't see where the memory allocate by strndup is ever freed.

Regards,

Bob Peterson
Red Hat File Systems