CVE-2024-49880: 
Linux Kernel vulnerability analysis and mitigation

CVE-2024-49880 addresses an off-by-one issue in the allocflexgd() function of the Linux kernel's ext4 filesystem implementation. The vulnerability was discovered when resizing an ext4 filesystem, triggering a kernel BUG at fs/ext4/resize.c:324. The issue affects Linux kernel versions from 6.8 up to (excluding) 6.10.14 and from 6.11 up to (excluding) 6.11.3 (NVD).

The vulnerability occurs in the allocflexgd() function when adjusting resizebg, where it was possible for flexgd->resizebg to be bigger than flexbgsize. The issue manifests when specific conditions are met during filesystem resizing operations, particularly when ogroup = flexbgsize 2 n and osize = (ogroup + 1) * group_size. The vulnerability has been assigned a CVSS v3.1 base score of 7.8 (HIGH) with vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H (Kernel Patch).

The vulnerability can lead to a kernel bug condition when attempting to resize an ext4 filesystem, potentially causing system crashes and denial of service. The high CVSS score indicates that successful exploitation could result in significant impacts to system confidentiality, integrity, and availability (NVD).

The issue has been fixed by removing the problematic plus 1 calculation and adding a WARNONONCE() check to prevent the issue from recurring. Users should update to Linux kernel versions 6.10.14, 6.11.3, or later that contain the fix. The patch has been backported to affected stable kernel versions (Kernel Patch).