CVE-2024-33847

CVE-2024-33847 is a medium-severity vulnerability rated 5.5/10 on the CVSS scale. In the Linux kernel, the following vulnerability has been resolved: f2fs: compress: don't allow unaligned truncation on released compress inode f2fs image may be corrupted after below testcase: - mkfs.f2fs -O extra_attr,compression -f /dev/vdb - mount /dev/vdb /mnt/f2fs - touch /mnt/f2fs/file - f2fs_io setflags compression /mnt/f2fs/file - dd if=/dev/zero of=/mnt/f2fs/file bs=4k count=4 - f2fs_io release_cblocks /mnt/f2fs/file - truncate -s 8192 /mnt/f2fs/file - umount /mnt/f2fs - fsck.f2fs /dev/vdb [ASSERT] (fsck_chk_inode_blk:1256) --> ino: 0x5 has i_blocks: 0x00000002, but has 0x3 blocks [FSCK] valid_block_count matching with CP [Fail] [0x4, 0x5] [FSCK] other corrupted bugs [Fail] The reason is: partial truncation assume compressed inode has reserved blocks, after partial truncation, valid block count may change w/o .i_blocks and .total_valid_block_count update, result in corruption. This patch only allow cluster size aligned truncation on released compress inode for fixing.. EPSS estimates a 0.23% chance of exploitation in the next 30 days.