Re: [PATCH] fs/ceph/mds_client: fix memory leaks in ceph_mdsc_build_path()

[Viacheslav Dubeyko]

On Tue, 2026-02-24 at 14:26 +0100, Max Kellermann wrote:
> Add __putname() calls to error code paths that did not free the "path"
> pointer obtained by __getname().  If ownership of this pointer is not
> passed to the caller via path_info.path, the function must free it
> before returning.
> 
> Fixes: 3fd945a79e14 ("ceph: encode encrypted name in ceph_mdsc_build_path and dentry release")
> Fixes: 550f7ca98ee0 ("ceph: give up on paths longer than PATH_MAX")
> Cc: stable@xxxxxxxxxxxxxxx
> Signed-off-by: Max Kellermann <max.kellermann@xxxxxxxxx>
> ---
>  fs/ceph/mds_client.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/fs/ceph/mds_client.c b/fs/ceph/mds_client.c
> index 23b6d00643c9..b1746273f186 100644
> --- a/fs/ceph/mds_client.c
> +++ b/fs/ceph/mds_client.c
> @@ -2768,6 +2768,7 @@ char *ceph_mdsc_build_path(struct ceph_mds_client *mdsc, struct dentry *dentry,
>  			if (ret < 0) {
>  				dput(parent);
>  				dput(cur);
> +				__putname(path);
>  				return ERR_PTR(ret);
>  			}
>  
> @@ -2777,6 +2778,7 @@ char *ceph_mdsc_build_path(struct ceph_mds_client *mdsc, struct dentry *dentry,
>  				if (len < 0) {
>  					dput(parent);
>  					dput(cur);
> +					__putname(path);
>  					return ERR_PTR(len);
>  				}
>  			}
> @@ -2813,6 +2815,7 @@ char *ceph_mdsc_build_path(struct ceph_mds_client *mdsc, struct dentry *dentry,
>  		 * cannot ever succeed.  Creating paths that long is
>  		 * possible with Ceph, but Linux cannot use them.
>  		 */
> +		__putname(path);
>  		return ERR_PTR(-ENAMETOOLONG);
>  	}

Makes sense. I think it could look better to have one place of processing error
case and calling __putname():

char *ceph_mdsc_build_path(struct ceph_mds_client *mdsc, struct dentry *dentry,
			   struct ceph_path_info *path_info, int for_wire)
{
    <main execution flow>

    return path + pos;

fail_build_path:
    __putname(path);
    return ERR_PTR(<error code>);
}

Reviewed-by: Viacheslav Dubeyko <Slava.Dubeyko@xxxxxxx>

Thanks,
Slava.