CVE-2021-47095: 
Linux Kernel vulnerability analysis and mitigation

CVE-2021-47095 affects the Linux kernel's IPMI SSIF (System Interface) driver. The vulnerability was discovered when ssif_info->client is dereferenced in an error path during probe, but it is set only after some error checking has already been done. This issue was disclosed on March 4, 2024, affecting Linux kernel versions from 5.4 up to 5.16-rc6 (NVD).

The vulnerability occurs in the IPMI SSIF driver where a NULL pointer dereference can happen at virtual address 0x88 during the probe function. The issue manifests when an error path is taken before ssif_info->client is properly initialized. This results in a kernel crash with a call trace showing the error occurring in __dev_printk and _dev_err functions. The vulnerability has been assigned a CVSS v3.1 Base Score of 5.5 (MEDIUM) with vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H (NVD).

When exploited, this vulnerability can cause a kernel crash due to the NULL pointer dereference, resulting in a denial of service condition. The impact is limited to local attacks and requires local user privileges to exploit (NVD).

The vulnerability requires local access and low privileges to exploit. It can be triggered during the IPMI SSIF driver probe process when certain error conditions are met. The issue has been confirmed to cause kernel crashes in affected systems (Kernel Patch).

The vulnerability has been fixed by initializing ssif_info->client before any error path can be taken and clearing i2c_client data in the error path to prevent the dangling pointer from leaking. The fix was implemented in kernel patch 34f35f8f14bc406efc06ee4ff73202c6fd245d15 (Kernel Patch).