Linux CVE-2026-80856

In the Linux kernel, the following vulnerability has been resolved:

fuse: fix invalidate lock leak on setattr writeback failure

fuse_do_setattr() takes filemap_invalidate_lock() for a DAX truncate (fault_blocked = true) and releases it at the out:/error: labels. But when a writeback flush is also needed, a write_inode_now() failure returns directly and leaks the lock, so any later fault or truncate on the file stalls on the stale rwsem.

For example, truncate(2) on a setuid file reaches fuse_do_setattr() with both ATTR_SIZE and ATTR_MODE set:

truncate(2) └─ do_truncate() ├─ dentry_needs_remove_privs()

S_ISUID

└─ notify_change()

KILL_SUID -> ATTR_MODE

└─ fuse_setattr()

no killpriv:

│

ia_valid |= ATTR_MODE

└─ fuse_do_setattr() ├─ filemap_invalidate_lock()

IS_DAX && is_truncate

└─ write_inode_now()

is_wb && ATTR_MODE

└─ if (err)

e.g. daemon -> -EIO

return err

<- lock leaked

Fix this by adding an unlock label that releases the lock before returning the error, and use it for the fuse_dax_break_layouts() failure path as well.