CVE-2026-80856: fuse: fix invalidate lock leak on setattr writeback failure

CVE-2026-80856: fuse: fix invalidate lock leak on setattr writeback failure

[Greg Kroah-Hartman]

From: Greg Kroah-Hartman <gregkh@kernel.org>

Description
===========

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.

The Linux kernel CVE team has assigned CVE-2026-80856 to this issue.


Affected and fixed versions
===========================

	Issue introduced in 5.10 with commit 6ae330cad6ef22ab8347ea9e0707dc56a7c7363f and fixed in 5.15.220 with commit 8f14906ce9103ab8f2f1ebda45935a0d61b9d763
	Issue introduced in 5.10 with commit 6ae330cad6ef22ab8347ea9e0707dc56a7c7363f and fixed in 6.1.187 with commit 03cfeeb135428fa83f0791d3f8f94d9298cae695
	Issue introduced in 5.10 with commit 6ae330cad6ef22ab8347ea9e0707dc56a7c7363f and fixed in 6.6.156 with commit 92588d187ba4697a322e7aefe5d9e538a87d1cd2
	Issue introduced in 5.10 with commit 6ae330cad6ef22ab8347ea9e0707dc56a7c7363f and fixed in 6.12.108 with commit ea9fea370b8de4ffd72e0ef89550415c15637787
	Issue introduced in 5.10 with commit 6ae330cad6ef22ab8347ea9e0707dc56a7c7363f and fixed in 6.18.49 with commit 1758730d9eaa3c06cf415c3446d9f6eed9ed3eed
	Issue introduced in 5.10 with commit 6ae330cad6ef22ab8347ea9e0707dc56a7c7363f and fixed in 7.1.13 with commit dd278d954c0e96a9cbd3cc491e07b8267d25f8d5
	Issue introduced in 5.10 with commit 6ae330cad6ef22ab8347ea9e0707dc56a7c7363f and fixed in 7.2.3 with commit e8457ebfd77a46e8d1210e8888ea914ad064558e
	Issue introduced in 5.10 with commit 6ae330cad6ef22ab8347ea9e0707dc56a7c7363f and fixed in 7.3-rc1 with commit 9afeca0d569c9fc89d758fe7a9339d1e8afb1546

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2026-80856
will be updated if fixes are backported, please check that for the most
up to date information about this issue.


Affected files
==============

The file(s) affected by this issue are:
	fs/fuse/dir.c


Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/8f14906ce9103ab8f2f1ebda45935a0d61b9d763
	https://git.kernel.org/stable/c/03cfeeb135428fa83f0791d3f8f94d9298cae695
	https://git.kernel.org/stable/c/92588d187ba4697a322e7aefe5d9e538a87d1cd2
	https://git.kernel.org/stable/c/ea9fea370b8de4ffd72e0ef89550415c15637787
	https://git.kernel.org/stable/c/1758730d9eaa3c06cf415c3446d9f6eed9ed3eed
	https://git.kernel.org/stable/c/dd278d954c0e96a9cbd3cc491e07b8267d25f8d5
	https://git.kernel.org/stable/c/e8457ebfd77a46e8d1210e8888ea914ad064558e
	https://git.kernel.org/stable/c/9afeca0d569c9fc89d758fe7a9339d1e8afb1546