CVE-2024-57923: 
Linux Kernel vulnerability analysis and mitigation

CVE-2024-57923 affects the Linux kernel's BTRFS filesystem implementation, specifically related to zlib compression on the s390 hardware compression path. The vulnerability was discovered and disclosed on January 19, 2025. The issue occurs in the zlib compression functionality where improper handling of input data length in zlib_compress_folios() can lead to read-in bytes exceeding the input range (NVD).

The vulnerability stems from incorrect calculation of strm.avail_in bytes in the s390 zlib hardware compression path. When the input data length passed to zlib_compress_folios() is arbitrary, setting strm.avail_in to a multiple of PAGE_SIZE can cause read-in bytes to exceed the input range. This triggers an assertion failure in btrfs_compress_folios() on debug kernels, specifically at fs/btrfs/compression.c:1041. The issue was introduced by commit fd1e75d0105d which made the compression path subpage compatible (Kernel Commit).

The vulnerability can trigger a kernel panic on systems running debug kernels with the affected code path. This results in a denial of service condition when the system encounters the specific compression scenario on s390 hardware (NVD).

The vulnerability requires access to a system using the BTRFS filesystem with zlib compression enabled on s390 hardware. It is triggered during normal filesystem operations when specific compression conditions are met (Debian Tracker).

The issue has been fixed by correcting the strm.avail_in calculation for the S390 hardware acceleration path. The fix involves using min(bytes_left, in_buf_folios << PAGE_SHIFT) instead of always using (in_buf_folios << PAGE_SHIFT) for the calculation (Kernel Commit).