CVE-2021-47301: 
Linux Kernel vulnerability analysis and mitigation

CVE-2021-47301 is a use-after-free vulnerability in the Linux kernel's Intel Gigabit Ethernet (igb) driver. The vulnerability was discovered in May 2024 and affects Linux kernel versions from 4.12 through 5.14-rc1. The issue occurs in the igb driver's TX ring cleaning functionality during controller reset operations (NVD).

The vulnerability stems from a failure to clean the next descriptor to watch (next_to_watch) when cleaning the TX ring. This oversight can lead to invalid memory accesses if igb_poll() runs while the controller is being reset, potentially causing the driver to attempt freeing a skb (socket buffer) that was already freed. The vulnerability has been assigned a CVSS v3.1 base score of 7.8 (HIGH) with the vector string CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H (NVD).

The vulnerability can lead to use-after-free conditions in the Linux kernel's network stack, potentially resulting in system crashes, memory corruption, or privilege escalation. The high CVSS score indicates that successful exploitation could have significant impacts on system confidentiality, integrity, and availability (NVD).

The vulnerability requires local access and low privileges to exploit. While the crash is reported to be harder to reproduce with the igb driver, the same potential problem exists in the igc driver as the code is identical (Kernel Patch).

The vulnerability has been patched in the Linux kernel by adding code to clean the next_to_watch pointer when cleaning the TX ring. The fix involves adding 'tx_buffer->next_to_watch = NULL' in the igb_clean_tx_ring function. Multiple stable kernel branches have received the patch (Kernel Patch).