CVE-2021-46924: 
Linux Kernel vulnerability analysis and mitigation

A memory leak vulnerability was discovered in the Linux kernel's NFC subsystem, specifically in the st21nfca driver (CVE-2021-46924). The issue occurs when 'phy->pending_skb' is allocated during device probe but not properly freed in the error handling and remove paths (Kernel Commit).

The vulnerability exists in the st21nfca_hci_i2c_probe function where memory is allocated for 'phy->pending_skb' but not properly freed in error conditions. The memory leak manifests as an unreferenced object of size 512 bytes, as demonstrated by the backtrace showing the allocation path through __kmalloc_node_track_caller, kmalloc_reserve, __alloc_skb, and st21nfca_hci_i2c_probe functions (Ubuntu Security, Red Hat Security).

The vulnerability results in a memory leak of 512 bytes per occurrence, which over time could lead to resource exhaustion in the system. This primarily affects systems using the ST21NFCA NFC chip driver (Ubuntu Security).

The issue has been fixed in various Linux kernel versions through patches that properly free 'pending_skb' in error and remove paths. Ubuntu has released fixes for affected versions: 5.4.0-105.119 for focal, 4.15.0-173.182 for bionic, and 4.4.0-258.292 for xenial (Ubuntu Security).