Dear Linux Kernel Maintainers, I hope this message finds you well. I am writing to report a potential vulnerability I encountered during testing of the Linux Kernel version v6.15. Git Commit: 0ff41df1cb268fc69e703a08a57ee14ae967d0ca (tag: v6.15) Bug Location: Bug report: https://hastebin.com/share/xafazazeve.yaml Complete log: https://hastebin.com/share/wopivucivi.perl Entire kernel config: https://hastebin.com/share/ajowibazak.ini Root Cause Analysis: The bug originates from bdev_getblk() in fs/buffer.c, where an invalid 1024-byte block size is requested on a device with a 2048-byte logical block size. The function does not enforce block size consistency, leading to downstream allocation failure in ext4_reserve_inode_write(). This failure is not gracefully handled, resulting in a persistent hang of the writeback worker thread, I/O errors, and filesystem instability. At present, I have not yet obtained a minimal reproducer for this issue. However, I am actively working on reproducing it, and I will promptly share any additional findings or a working reproducer as soon as it becomes available. Thank you very much for your time and attention to this matter. I truly appreciate the efforts of the Linux kernel community. Best regards, John
