Key Information Summary Vulnerability Type: refcount underflow in ext4 filesystem Affected Code: - - Specific function: Issue Description: syzkaller discovered that reads an EA inode refcount that is already ≤ 0, then applies (typically -1). This causes a refcount underflow, and the process continues with an incorrect value, triggering errors such as: Fix: - Explicitly enforce an invariant: if the current refcount is non-positive, treat it as disk data corruption, call , and return instead of updating the refcount. - Remove since negative refcounts are now impossible; retain error reporting within . Impact: Prevents refcount underflow and subsequent orphan cleanup operations. Fix Commit Details: - Commit ID: - Author: Ahmet Eray Karadag - Committer: Greg Kroah-Hartman - Date: 2025-09-20 Bug Report: - Reporter: syzbot+0be4f339a8218d2a5bb1@syzkaller.appspotmail.com - Related Link: https://syzbot.org/bug?extid=0be4f339a8218d2a5bb1