On Fri, Dec 22, 2017 at 03:32:29PM +0100, Dongsu Park wrote: > From: Seth Forshee <seth.forshee@xxxxxxxxxxxxx> > > Superblock level remounts are currently restricted to global > CAP_SYS_ADMIN, as is the path for changing the root mount to > read only on umount. Loosen both of these permission checks to > also allow CAP_SYS_ADMIN in any namespace which is privileged > towards the userns which originally mounted the filesystem. > > Patch v4 is available: https://patchwork.kernel.org/patch/8944631/ > > Cc: linux-fsdevel@xxxxxxxxxxxxxxx > Cc: linux-kernel@xxxxxxxxxxxxxxx > Cc: Alexander Viro <viro@xxxxxxxxxxxxxxxxxx> > Cc: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx> > Cc: Serge Hallyn <serge@xxxxxxxxxx> Acked-by: Serge Hallyn <serge@xxxxxxxxxx> > Signed-off-by: Seth Forshee <seth.forshee@xxxxxxxxxxxxx> > Signed-off-by: Dongsu Park <dongsu@xxxxxxxxxx> > --- > fs/namespace.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/fs/namespace.c b/fs/namespace.c > index e158ec6b..830040d7 100644 > --- a/fs/namespace.c > +++ b/fs/namespace.c > @@ -1589,7 +1589,7 @@ static int do_umount(struct mount *mnt, int flags) > * Special case for "unmounting" root ... > * we just try to remount it readonly. > */ > - if (!capable(CAP_SYS_ADMIN)) > + if (!ns_capable(sb->s_user_ns, CAP_SYS_ADMIN)) > return -EPERM; > down_write(&sb->s_umount); > if (!sb_rdonly(sb)) > @@ -2327,7 +2327,7 @@ static int do_remount(struct path *path, int ms_flags, int sb_flags, > down_write(&sb->s_umount); > if (ms_flags & MS_BIND) > err = change_mount_flags(path->mnt, ms_flags); > - else if (!capable(CAP_SYS_ADMIN)) > + else if (!ns_capable(sb->s_user_ns, CAP_SYS_ADMIN)) > err = -EPERM; > else > err = do_remount_sb(sb, sb_flags, data, 0); > -- > 2.13.6
