CVE-2026-64064: In the Linux kernel, the following vulnerability has been resolved: netfs: Fix netfs_invalidate_folio() to clear dirty bit if all changes gone If a ...

Description

In the Linux kernel, the following vulnerability has been resolved: netfs: Fix netfs_invalidate_folio() to clear dirty bit if all changes gone If a streaming write is made, this will leave the relevant modified folio in a not-uptodate, but dirty state with a netfs_folio struct hung off of folio->private indicating the dirty range. Subsequently truncating the file such that the dirty data in the folio is removed, but the first part of the folio theoretically remains will cause the netfs_folio struct to be discarded... but will leave the dirty flag set. If the folio is then read via mmap(), netfs_read_folio() will see that the page is dirty and jump to netfs_read_gaps() to fill in the missing bits. netfs_read_gaps(), however, expects there to be a netfs_folio struct present and can oops because truncate removed it. Fix this by calling folio_cancel_dirty() in netfs_invalidate_folio() in the event that all the dirty data in the folio is erased (as nfs does). Also add some tracepoints to log modifications to a dirty page. This can be reproduced with something like: dd if=/dev/zero of=/xfstest.test/foo bs=1M count=1 umount /xfstest.test mount /xfstest.test xfs_io -c "w 0xbbbf 0xf96c" \ -c "truncate 0xbbbf" \ -c "mmap -r 0xb000 0x11000" \ -c "mr 0xb000 0x11000" \ /xfstest.test/foo with fscaching disabled (otherwise streaming writes are suppressed) and a change to netfs_perform_write() to disallow streaming writes if the fd is open O_RDWR: if (//(file->f_mode & FMODE_READ) || <--- comment this out netfs_is_cache_enabled(ctx)) { It should be reproducible even without this change, but if prevents the above trivial xfs_io command from reproducing it. Note that the initial dd is important: the file must start out sufficiently large that the zero-point logic doesn't just clear the gaps because it knows there's nothing in the file to read yet. Unmounting and mounting is needed to clear the pagecache (there are other ways to do that that may also work). This was initially reproduced with the generic/522 xfstest on some patches that remove the FMODE_READ restriction.

Metrics

EPSS Probability

0.17%

6.4th percentile

Probability of exploitation in the next 30 days. Learn more

Affected Software

Source: CNA advisory (CVE.org). NVD analysis pending.

Vendor	Product	Versions
Linux	Linux	>= 9ebff83e648148b9ece97d4e4890dd84ca54d6ce, < 31ba145faceb378fa01afcb8349e15ea7d95e542; >= 9ebff83e648148b9ece97d4e4890dd84ca54d6ce, < fb6ec883b48b8789e5e690dcd440d2db941e840c; >= 9ebff83e648148b9ece97d4e4890dd84ca54d6ce, < 65ae8717abf36202fef02260b64b781d2d44a9bf; >= 9ebff83e648148b9ece97d4e4890dd84ca54d6ce, < 156ac2ec2ee77c44c4eb7439d6d165247ba12247
Linux	Linux	6.8

References

Timeline

Published: Jul 19, 2026
Last Modified: Jul 30, 2026
Status: Awaiting Analysis

Frequently Asked Questions

What is CVE-2026-64064?

In the Linux kernel, the following vulnerability has been resolved: netfs: Fix netfs_invalidate_folio() to clear dirty bit if all changes gone If a streaming write is made, this will leave the relevant modified folio in a not-uptodate, but dirty state with a netfs_folio struct hung off of folio->private indicating the dirty range. Subsequently truncating the file such that the dirty data in the folio is removed, but the first part of the folio theoretically remains will cause the netfs_folio struct to be discarded... but will leave the dirty flag set. If the folio is then read via mmap(), netfs_read_folio() will see that the page is dirty and jump to netfs_read_gaps() to fill in the missing bits. netfs_read_gaps(), however, expects there to be a netfs_folio struct present and can oops because truncate removed it. Fix this by calling folio_cancel_dirty() in netfs_invalidate_folio() in the event that all the dirty data in the folio is erased (as nfs does). Also add some tracepoints to log modifications to a dirty page. This can be reproduced with something like: dd if=/dev/zero of=/xfstest.test/foo bs=1M count=1 umount /xfstest.test mount /xfstest.test xfs_io -c "w 0xbbbf 0xf96c" \ -c "truncate 0xbbbf" \ -c "mmap -r 0xb000 0x11000" \ -c "mr 0xb000 0x11000" \ /xfstest.test/foo with fscaching disabled (otherwise streaming writes are suppressed) and a change to netfs_perform_write() to disallow streaming writes if the fd is open O_RDWR: if (//(file->f_mode & FMODE_READ) || <--- comment this out netfs_is_cache_enabled(ctx)) { It should be reproducible even without this change, but if prevents the above trivial xfs_io command from reproducing it. Note that the initial dd is important: the file must start out sufficiently large that the zero-point logic doesn't just clear the gaps because it knows there's nothing in the file to read yet. Unmounting and mounting is needed to clear the pagecache (there are other ways to do that that may also work). This was initially reproduced with the generic/522 xfstest on some patches that remove the FMODE_READ restriction.

How severe is CVE-2026-64064?

Severity scoring for CVE-2026-64064 is pending analysis. The EPSS model estimates a 0.17% probability of exploitation in the next 30 days.

How do I fix CVE-2026-64064?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

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