Quoting Aristeu Rozanski (a...@redhat.com):
> Initial implementation of the uid/gid maps will enforce that the
> maps should be in order and would prevent a use case like this from
> being used:
> 0 1000 1
> 48 500 1
>
> since the second entry both values should be bigger than the previous.
> This patch implements a more elaborate collision detection allowing any
> order to be used.
>
> Cc: "Eric W. Biederman" <ebied...@xmission.com>
> Cc: "Serge E. Hallyn" <se...@hallyn.com>
I *think* that looks just right :)
Acked-by: Serge Hallyn <serge.hal...@canonical.com>
> Signed-off-by: Aristeu Rozanski <a...@redhat.com>
>
> diff --git a/kernel/user_namespace.c b/kernel/user_namespace.c
> index 2b042c4..fb0e492 100644
> --- a/kernel/user_namespace.c
> +++ b/kernel/user_namespace.c
> @@ -521,6 +521,28 @@ struct seq_operations proc_projid_seq_operations = {
>
> static DEFINE_MUTEX(id_map_mutex);
>
> +#define in_range(b,first,len) ((b)>=(first)&&(b)<(first)+(len))
> +static inline int extent_collision(struct uid_gid_map *new_map,
> + struct uid_gid_extent *extent)
> +{
> + int i;
> + struct uid_gid_extent *cur;
> +
> + for (i = 0; i < new_map->nr_extents; i++) {
> + cur = &new_map->extent[i];
> + if (in_range(extent->first, cur->first, cur->count) ||
> + in_range(extent->first + extent->count, cur->first,
> + cur->count))
> + return 1;
> + if (in_range(extent->lower_first, cur->lower_first,
> + cur->count) ||
> + in_range(extent->lower_first + extent->count,
> + cur->lower_first, cur->count))
> + return 1;
> + }
> + return 0;
> +}
> +
> static ssize_t map_write(struct file *file, const char __user *buf,
> size_t count, loff_t *ppos,
> int cap_setid,
> @@ -634,10 +656,7 @@ static ssize_t map_write(struct file *file, const char
> __user *buf,
> if ((extent->lower_first + extent->count) <=
> extent->lower_first)
> goto out;
>
> - /* For now only accept extents that are strictly in order */
> - if (last &&
> - (((last->first + last->count) > extent->first) ||
> - ((last->lower_first + last->count) > extent->lower_first)))
> + if (extent_collision(&new_map, extent))
> goto out;
>
> new_map.nr_extents++;
--
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