Bug 2492297 (CVE-2026-53029)

Summary: CVE-2026-53029 kernel: fs/ntfs3: prevent uninitialized lcn caused by zero len
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
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Priority: medium    
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` filesystem driver. This vulnerability occurs due to an uninitialized local variable (`lcn`) when handling zero-length data during I/O operations. An attacker could potentially exploit this flaw to cause a denial of service or information disclosure due to unpredictable behavior resulting from the use of uninitialized memory.
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Description OSIDB Bzimport 2026-06-24 18:04:12 UTC 
In the Linux kernel, the following vulnerability has been resolved:

fs/ntfs3: prevent uninitialized lcn caused by zero len

syzbot reported a uninit-value in ntfs_iomap_begin [1].

Since runs was not touched yet, run_lookup_entry() immediately fails
and returns false, which makes the value of "*len" 0.
Simultaneously, the new value and err value are also 0, causing the
logic in attr_data_get_block_locked() to jump directly to ok, ultimately
resulting in *lcn being triggered before it is set [1].

In ntfs_iomap_begin(), the check for a 0 value in clen is moved forward
to before updating lcn to avoid this [1].

[1]
BUG: KMSAN: uninit-value in ntfs_iomap_begin+0x8c0/0x1460 fs/ntfs3/inode.c:825
 ntfs_iomap_begin+0x8c0/0x1460 fs/ntfs3/inode.c:825
 iomap_iter+0x9b7/0x1540 fs/iomap/iter.c:110

Local variable lcn created at:
 ntfs_iomap_begin+0x15d/0x1460 fs/ntfs3/inode.c:786
Comment 1 Keith Grant 2026-06-26 17:24:30 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2026062454-CVE-2026-53029-4cfc@gregkh/T