CVE-2026-80856

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CVE-2026-80856

Summary: fuse: fix invalidate lock leak on setattr writeback failure

Details: 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.

References: https://git.kernel.org/stable/c/03cfeeb135428fa83f0791d3f8f94d9298cae695, https://git.kernel.org/stable/c/1758730d9eaa3c06cf415c3446d9f6eed9ed3eed, https://git.kernel.org/stable/c/8f14906ce9103ab8f2f1ebda45935a0d61b9d763, https://git.kernel.org/stable/c/92588d187ba4697a322e7aefe5d9e538a87d1cd2, https://git.kernel.org/stable/c/9afeca0d569c9fc89d758fe7a9339d1e8afb1546, https://git.kernel.org/stable/c/dd278d954c0e96a9cbd3cc491e07b8267d25f8d5, https://git.kernel.org/stable/c/e8457ebfd77a46e8d1210e8888ea914ad064558e, https://git.kernel.org/stable/c/ea9fea370b8de4ffd72e0ef89550415c15637787, https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/80xxx/CVE-2026-80856.json, https://nvd.nist.gov/vuln/detail/CVE-2026-80856, https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git