/*
* Pointer dereferencing. We don't trust the shm_ref, so we validate
* both the index and offset with known boundaries.
+ *
+ * "shmp" and "shmp_index" guarantee that it's safe to use the pointer
+ * target type, even in the occurrence of shm_ref modification by an
+ * untrusted process having write access to the shm_ref. We return a
+ * NULL pointer if the ranges are invalid.
*/
static inline
char *_shmp_offset(struct shm_object_table *table, struct shm_ref *ref,
- size_t offset)
+ size_t idx, size_t elem_size)
{
struct shm_object *obj;
- size_t index, ref_offset;
+ size_t objindex, ref_offset;
- index = (size_t) ref->index;
- if (unlikely(index >= table->allocated_len))
+ objindex = (size_t) ref->index;
+ if (unlikely(objindex >= table->allocated_len))
return NULL;
- obj = &table->objects[index];
+ obj = &table->objects[objindex];
ref_offset = (size_t) ref->offset;
- ref_offset += offset;
- if (unlikely(ref_offset >= obj->memory_map_size))
+ ref_offset += idx * elem_size;
+ /* Check if part of the element returned would exceed the limits. */
+ if (unlikely(ref_offset + elem_size > obj->memory_map_size))
return NULL;
return &obj->memory_map[ref_offset];
}
-#define shmp_index(handle, ref, offset) \
+#define shmp_index(handle, ref, index) \
({ \
__typeof__((ref)._type) ____ptr_ret; \
- ____ptr_ret = (__typeof__(____ptr_ret)) _shmp_offset((handle)->table, &(ref)._ref, ((offset) * sizeof(*____ptr_ret))); \
+ ____ptr_ret = (__typeof__(____ptr_ret)) _shmp_offset((handle)->table, &(ref)._ref, index, sizeof(*____ptr_ret)); \
____ptr_ret; \
})
return obj->wait_fd[0];
}
+static inline
+int shm_get_object_data(struct shm_handle *handle, struct shm_ref *ref,
+ int *shm_fd, int *wait_fd, uint64_t *memory_map_size)
+{
+ struct shm_object_table *table = handle->table;
+ struct shm_object *obj;
+ size_t index;
+
+ index = (size_t) ref->index;
+ if (unlikely(index >= table->allocated_len))
+ return -EPERM;
+ obj = &table->objects[index];
+ *shm_fd = obj->shm_fd;
+ *wait_fd = obj->wait_fd[0];
+ *memory_map_size = obj->memory_map_size;
+ return 0;
+}
+
#endif /* _LIBRINGBUFFER_SHM_H */