CVE-2021-47080: 
Linux Kernel vulnerability analysis and mitigation

CVE-2021-47080 affects the Linux kernel's RDMA/core component. The vulnerability was discovered in the handling of user-supplied entry sizes in the GID table query functionality. When a user supplies a zero value for user_entry_size, it can trigger a divide-by-zero error in the ib_uverbs_handler_UVERBS_METHOD_QUERY_GID_TABLE function (NVD, Kernel Patch).

The vulnerability exists in the RDMA/core subsystem where the user_entry_size parameter, supplied by the user, is used as a denominator to calculate the number of entries. When a zero value is provided, it leads to a divide-by-zero error in the kernel. The issue affects Linux kernel versions from 5.10 up to (excluding) 5.10.40, from 5.11 up to (excluding) 5.12.7, and versions 5.13-rc1 and 5.13-rc2. 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 successfully exploited, this vulnerability can cause a kernel crash through a divide-by-zero error, resulting in a denial of service condition. The impact is limited to availability, with no direct impact on confidentiality or integrity of the system (NVD).

The vulnerability requires local access and can be triggered through the ioctl system call when interacting with the RDMA/uverbs interface. An attacker needs local access to the system and sufficient privileges to interact with the RDMA subsystem (NVD).

The vulnerability has been fixed by adding a check for zero value of user_entry_size before using it as a denominator. The fix returns -EINVAL when a zero value is detected. Users should upgrade to Linux kernel versions 5.10.40, 5.12.7 or later that include the security fix (Kernel Patch).