Bug 2467158 (CVE-2026-43127)

Summary: CVE-2026-43127 kernel: ntfs3: fix circular locking dependency in run_unpack_ex
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security <prodsec-ir-bot>
Status: NEW --- QA Contact:
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Version: unspecifiedCC: rhel-process-autobot, watson-tool-maintainers
Target Milestone: ---Keywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in the Linux kernel's ntfs3 component. This vulnerability involves a circular locking dependency, also known as an AB-BA deadlock, which can occur when the system attempts to acquire two specific locks in a conflicting order. This issue can cause the system to become unresponsive, leading to a Denial of Service (DoS).
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Description OSIDB Bzimport 2026-05-06 13:07:38 UTC 
In the Linux kernel, the following vulnerability has been resolved:

ntfs3: fix circular locking dependency in run_unpack_ex

Syzbot reported a circular locking dependency between wnd->rw_lock
(sbi->used.bitmap) and ni->file.run_lock.

The deadlock scenario:
1. ntfs_extend_mft() takes ni->file.run_lock then wnd->rw_lock.
2. run_unpack_ex() takes wnd->rw_lock then tries to acquire
   ni->file.run_lock inside ntfs_refresh_zone().

This creates an AB-BA deadlock.

Fix this by using down_read_trylock() instead of down_read() when
acquiring run_lock in run_unpack_ex(). If the lock is contended,
skip ntfs_refresh_zone() - the MFT zone will be refreshed on the
next MFT operation. This breaks the circular dependency since we
never block waiting for run_lock while holding wnd->rw_lock.
Comment 1 Keith Grant 2026-05-06 17:50:55 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2026050620-CVE-2026-43127-aa44@gregkh/T