CVE-2025-38709

In the Linux kernel, the following vulnerability has been resolved:<br /> <br /> loop: Avoid updating block size under exclusive owner<br /> <br /> Syzbot came up with a reproducer where a loop device block size is<br /> changed underneath a mounted filesystem. This causes a mismatch between<br /> the block device block size and the block size stored in the superblock<br /> causing confusion in various places such as fs/buffer.c. The particular<br /> issue triggered by syzbot was a warning in __getblk_slow() due to<br /> requested buffer size not matching block device block size.<br /> <br /> Fix the problem by getting exclusive hold of the loop device to change<br /> its block size. This fails if somebody (such as filesystem) has already<br /> an exclusive ownership of the block device and thus prevents modifying<br /> the loop device under some exclusive owner which doesn&amp;#39;t expect it.