CVE-2026-80855: fuse: fix invalidate lock leak on open O_TRUNC DAX failure

CVE-2026-80855: fuse: fix invalidate lock leak on open O_TRUNC DAX 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 open O_TRUNC DAX failure

fuse_open() takes filemap_invalidate_lock() for a DAX truncate
(dax_truncate = true) and releases it before the out_inode_unlock
label.  But when fuse_dax_break_layouts() fails, the goto
out_inode_unlock skips the unlock and leaks the rwsem, so any later
fault or truncate on the file stalls on the stale lock.

fuse_dax_break_layouts() can fail with -ERESTARTSYS when a signal
interrupts the wait for busy DAX pages to drain:

  open("file", O_RDWR | O_TRUNC)
  └─ fuse_open()
     ├─ filemap_invalidate_lock()        # dax_truncate
     └─ fuse_dax_break_layouts()
        └─ dax_break_layout()
           └─ wait_page_idle()           # TASK_INTERRUPTIBLE
              └─ fuse_wait_dax_page()    # unlock, schedule, re-lock
                 └─ signal → -ERESTARTSYS
     goto out_inode_unlock               # <- lock leaked

Fix this by moving filemap_invalidate_unlock() below the label so
that all error paths release the lock, and rename the label to
out_unlock as it now covers more than just the inode lock.

The Linux kernel CVE team has assigned CVE-2026-80855 to this issue.


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

	Issue introduced in 5.15.109 with commit d58366aab86854217b81679d1a9dcd54a2edfc2a and fixed in 5.15.220 with commit 1b04d80a27d317064cce2307472f5bef9975bc50
	Issue introduced in 6.0 with commit 2fdbb8dd01556e1501132b5ad3826e8f71e24a8b and fixed in 6.1.187 with commit a61524da59a2f5ac9c8de23ff98b30da769ab144
	Issue introduced in 6.0 with commit 2fdbb8dd01556e1501132b5ad3826e8f71e24a8b and fixed in 6.6.156 with commit dcf30a56624c2a0cfab1bada5b1ca8cc0c02f010
	Issue introduced in 6.0 with commit 2fdbb8dd01556e1501132b5ad3826e8f71e24a8b and fixed in 6.12.108 with commit 7288c279ddbd654a06c82118c1a3f5570c1807f0
	Issue introduced in 6.0 with commit 2fdbb8dd01556e1501132b5ad3826e8f71e24a8b and fixed in 6.18.49 with commit 776e85fda752f9a15e0f82dec42ecacd12a9bd94
	Issue introduced in 6.0 with commit 2fdbb8dd01556e1501132b5ad3826e8f71e24a8b and fixed in 7.1.13 with commit 1d3e701cda2f41d48aa721b3ebefbe0fbf8d74da
	Issue introduced in 6.0 with commit 2fdbb8dd01556e1501132b5ad3826e8f71e24a8b and fixed in 7.2.3 with commit e981474d7bf1457da12404e169ea147d2c8ecea7
	Issue introduced in 6.0 with commit 2fdbb8dd01556e1501132b5ad3826e8f71e24a8b and fixed in 7.3-rc1 with commit a927f1867e61b78f39f9da0bbba3c98c2ca151fe
	Issue introduced in 5.10.179 with commit 81775ab858b4236c52c5da7e25cec6e49dd91b46
	Issue introduced in 5.18.18 with commit b57e150ac2eac791d5d187923b73dc2dafaf67fa
	Issue introduced in 5.19.2 with commit 1fdbbe246daf348adaa0739463384b16ceba1fc0

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-2026-80855
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/file.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/1b04d80a27d317064cce2307472f5bef9975bc50
	https://git.kernel.org/stable/c/a61524da59a2f5ac9c8de23ff98b30da769ab144
	https://git.kernel.org/stable/c/dcf30a56624c2a0cfab1bada5b1ca8cc0c02f010
	https://git.kernel.org/stable/c/7288c279ddbd654a06c82118c1a3f5570c1807f0
	https://git.kernel.org/stable/c/776e85fda752f9a15e0f82dec42ecacd12a9bd94
	https://git.kernel.org/stable/c/1d3e701cda2f41d48aa721b3ebefbe0fbf8d74da
	https://git.kernel.org/stable/c/e981474d7bf1457da12404e169ea147d2c8ecea7
	https://git.kernel.org/stable/c/a927f1867e61b78f39f9da0bbba3c98c2ca151fe