CVE-2021-47592: 
Linux Kernel vulnerability analysis and mitigation

CVE-2021-47592 affects the Linux kernel's traffic control (tc) flower deletion functionality for VLAN priority Rx steering in the STMMAC driver. The vulnerability was discovered in June 2024 and affects Linux kernel versions from 5.13 up to (excluding) 5.15.11, as well as 5.16-rc1 through 5.16-rc5 (NVD).

The vulnerability stems from an incorrect implementation of tc_del_vlan_flow() that uses flow_cls_offload_flow_rule() to get struct flow_rule *rule which becomes invalid during tc filter delete operations. This leads to a NULL pointer dereference when attempting to delete VLAN priority-based frame steering rules (Kernel Patch).

When triggered, this vulnerability causes a kernel NULL pointer dereference, resulting in a kernel panic. This can lead to system crashes and potential denial of service conditions (NVD).

The vulnerability can be triggered by attempting to delete a tc flower filter for VLAN priority-based frame steering. A specific sequence of operations involving adding and then deleting VLAN priority-based traffic control rules can trigger the NULL pointer dereference (Kernel Patch).

The issue has been fixed by introducing stmmac_rfs_entry as a driver-side flow_cls_offload record for 'RX frame steering' tc flower. The fix ensures proper tracking and cleanup of VLAN priority-based frame steering rules. Users should update to Linux kernel version 5.15.11 or later to receive the fix (Kernel Patch).