CVE-2021-3493

In the Linux kernel, the batman-adv module's dat handling updated MAC addresses using a simple copy, which could be partially observed by parallel readers. A reader might transport a half-updated MAC address over the network or use it in ARP responses, poisoning the ARP cache. The fix uses atomic64_t to store the 48-bit MAC address, ensuring readers see either the old or new address, never a mixture.

A bug in the Linux kernel's I3C subsystem causes recursive locking during registration of new I3C devices. The function i3c_master_register_new_i3c_devs() registers devices while holding i3c_bus_normaluse_lock(), and device_register() can immediately trigger a probe callback that tries to acquire the same lock again, leading to a deadlock. The fix separates device creation from registration and uses the maintenance lock.

In the Linux kernel, the dm-pcache module did not validate cache segment IDs from persistent memory before indexing into cache->segments[]. With only CRC protection using a public seed, an attacker with CAP_SYS_ADMIN supplying the cache device could cause out-of-bounds reads and writes via crafted metadata. The fix adds validation and rejects invalid segment IDs with -EIO.

The Linux kernel's i3c master subsystem had a use-after-free vulnerability in the master->this pointer. Sysfs attribute callbacks dereferenced master->this, which was freed in i3c_master_detach_free_devs() before the master device was released. The fix keeps master->this alive until i3c_masterdev_release() and resets it on error paths.

In the Linux kernel, the i3c_master_search_i3c_dev_duplicate() function that searches for duplicate I3C devices can incorrectly match the master device itself (master->this), returning the controller as a duplicate. Since the controller is not a target device, it cannot be a duplicate of one. The fix excludes master->this from matching.

In the Linux kernel, the dm-pcache module does not validate the persisted dirty_tail chain at load. A crafted image, whose on-media fields are authenticated only by a crc32c with a fixed seed, can aim dirty_tail at a chain of last ksets that never terminates, causing cache_writeback_fn() to re-arm itself forever. The fix adds validation of the dirty_tail chain at load with a hop cap.

A bug in the Linux kernel's memcg subsystem causes LRU size accounting to be copied to the parent instead of moved when a memory cgroup is offlined, leaving stale counters on the child. This makes the LRU (or MGLRU) scanner read phantom sizes and grind through empty lists on dying cgroups, over-budgeting limits and wasting CPU. On one host, counters described 476 GiB of pages—1.89x the machine's RAM.

A use-after-free vulnerability was found in the Linux kernel's virtio_pmem driver for NVDIMM persistent memory. The issue occurs when a request has already been freed by the submitter but is still reachable via the virtqueue, leading to waking up freed memory during interrupt handling.

In the Linux kernel, the drm/bridge synopsys dw-dp driver initializes and registers the DisplayPort AUX channel during dw_dp_bind(), but never unregisters it. This may lead to resource leaks and/or use-after-free. The fix adds the missing dw_dp_unbind() function to allow cleanup.

In the Linux kernel, the drm/rockchip dw_dp driver initializes and registers core resources such as the DisplayPort AUX channel during dw_dp_bind(), but never unregisters them. This leads to memory leaks and/or use-after-free, as shown in a KASAN report. The issue is fixed by using the exported dw_dp_unbind() function in the component's unbind() callback and in its bind() error path.