CVE-2026-97439: fs/ntfs3: preserve non-DOS attribute bits in system.dos_attrib
In the Linux kernel, the following vulnerability has been resolved:
fs/ntfs3: preserve non-DOS attribute bits in system.dosattrib
[BUG] A corrupted ntfs3 image can hit a NULL function pointer call in genericperformwrite() after toggling system.ntfsattrib and then overwriting system.dosattrib on the same file.
BUG: kernel NULL pointer dereference, address: 0000000000000000 \#PF: supervisor instruction fetch in kernel mode \#PF: errorcode(0x0010) - not-present page PGD bed5067 P4D bed5067 PUD 0 Oops: Oops: 0010 [#1] SMP KASAN NOPTI RIP: 0010:0x0 Code: Unable to access opcode bytes at 0xffffffffffffffd6. RSP: 0018:ffff88801025f988 EFLAGS: 00010246 Call Trace: genericperformwrite+0x409/0x8c0 mm/filemap.c:4255 genericfilewriteiter+0x1bb/0x200 mm/filemap.c:4372 ntfsfilewriteiter+0xcd9/0x1c20 fs/ntfs3/file.c:1253 newsyncwrite fs/readwrite.c:593 [inline] vfswrite+0x63b/0xf70 fs/readwrite.c:686 ksyswrite+0x133/0x250 fs/readwrite.c:738 dosyswrite fs/readwrite.c:749 [inline] sesyswrite fs/readwrite.c:746 [inline] x64syswrite+0x77/0xc0 fs/readwrite.c:746 ...
[CAUSE] system.ntfsattrib updates ATTRDATA flags via ninewattrflags() and switches imapping->aops to ntfsaopscmpr when FILEATTRIBUTECOMPRESSED is set. system.dosattrib then overwrites ni->stdfa from a one-byte DOS attribute value, clearing the compression bit without updating ATTRDATA or the mapping operations.
Old buffered writes use iscompressed(ni) to choose genericfilewriteiter(). That leaves genericperformwrite() calling a NULL writebegin callback from ntfsaopscmpr.
[FIX] Treat system.dosattrib as a low-byte DOS attribute update and preserve the existing non-DOS attribute bits in ni->stdfa. This keeps compressed and sparse state consistent with ATTRDATA and the mapping operations while keeping the existing DOS attribute semantics intact.
Affected Software
Event History
Frequently Asked Questions
What conditions are required to trigger this issue?
A corrupted NTFS3 image is required. The trigger involves toggling the system.ntfs_attrib extended attribute and then overwriting system.dos_attrib on the same file, followed by a write operation.
What is the observed impact when the issue is triggered?
The kernel can make a NULL function-pointer call in generic_perform_write(), resulting in a kernel NULL pointer dereference and Oops during a file write.
How can administrators determine whether they may be affected?
Systems using the Linux kernel NTFS3 filesystem driver may be exposed when handling corrupted NTFS3 images. Kernel logs showing an Oops with an instruction fetch at address 0x0 and a call trace through generic_perform_write(), ntfs_file_write_iter(), and vfs_write() match the reported failure.
Is a fix available?
Yes. The issue is described as resolved, and the provided stable kernel references identify commits containing the fix.