On Sun, Jul 19, 2020 at 12:04:14PM +0200, Adrian Reber wrote:
> Opening files in /proc/pid/map_files when the current user is
> CAP_CHECKPOINT_RESTORE capable in the root namespace is useful for
> checkpointing and restoring to recover files that are unreachable via
> the file system such as deleted files, or memfd files.
>
> Signed-off-by: Adrian Reber <areber@xxxxxxxxxx>
Reviewed-by: Serge Hallyn <serge@xxxxxxxxxx>
> Signed-off-by: Nicolas Viennot <Nicolas.Viennot@xxxxxxxxxxxx>
> Reviewed-by: Cyrill Gorcunov <gorcunov@xxxxxxxxx>
> ---
> fs/proc/base.c | 8 ++++----
> 1 file changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/fs/proc/base.c b/fs/proc/base.c
> index 65893686d1f1..b824a8c89011 100644
> --- a/fs/proc/base.c
> +++ b/fs/proc/base.c
> @@ -2194,16 +2194,16 @@ struct map_files_info {
> };
>
> /*
> - * Only allow CAP_SYS_ADMIN to follow the links, due to concerns about how the
> - * symlinks may be used to bypass permissions on ancestor directories in the
> - * path to the file in question.
> + * Only allow CAP_SYS_ADMIN and CAP_CHECKPOINT_RESTORE to follow the links, due
> + * to concerns about how the symlinks may be used to bypass permissions on
> + * ancestor directories in the path to the file in question.
> */
> static const char *
> proc_map_files_get_link(struct dentry *dentry,
> struct inode *inode,
> struct delayed_call *done)
> {
> - if (!capable(CAP_SYS_ADMIN))
> + if (!checkpoint_restore_ns_capable(&init_user_ns))
> return ERR_PTR(-EPERM);
>
> return proc_pid_get_link(dentry, inode, done);
> --
> 2.26.2
