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>
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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