In the Linux kernel, the following vulnerability has been resolved:
smb: client: flush and commit data before querying allocated ranges
The mode 0 / FALLOC_FL_KEEP_SIZE fallocate emulation for small interior
ranges in smb3_simple_fallocate_range() issues
FSCTL_QUERY_ALLOCATED_RANGES and zero-fills any sub-range the server
reports as an unallocated hole, to force block allocation without
changing file contents.
This is unsafe against Windows servers. Per the Win32 documentation,
FSCTL_QUERY_ALLOCATED_RANGES only reports ranges that *may* contain
nonzero data and is explicitly not coherent with recently written data:
"a call to FSCTL_QUERY_ALLOCATED_RANGES [after writing to a network
file] would not necessarily return a correct list of allocated
regions. To ensure coherency [...] flush the data to the file"
fsx (generic/363) reproduces the resulting corruption against Windows
Server 2022: a range is written, an uncached read returns the data, yet
the next FSCTL_QUERY_ALLOCATED_RANGES on that range reports it as a whole
hole, so the emulation overwrites live data with zeroes. A network trace
confirmed the WRITE, the READ returning data and the query returning an
empty range list within microseconds. Samba does not exhibit this; its
query is coherent with the written data.
Write back the dirty pages, drain any outstanding I/O and issue an SMB2
FLUSH to force the server to commit the data before querying the
allocated ranges, so the query reflects the data actually present.
With this, generic/363 passes against both Windows Server 2022 and Samba
over 100000 fsx operations.
smb: client: flush and commit data before querying allocated ranges
The mode 0 / FALLOC_FL_KEEP_SIZE fallocate emulation for small interior
ranges in smb3_simple_fallocate_range() issues
FSCTL_QUERY_ALLOCATED_RANGES and zero-fills any sub-range the server
reports as an unallocated hole, to force block allocation without
changing file contents.
This is unsafe against Windows servers. Per the Win32 documentation,
FSCTL_QUERY_ALLOCATED_RANGES only reports ranges that *may* contain
nonzero data and is explicitly not coherent with recently written data:
"a call to FSCTL_QUERY_ALLOCATED_RANGES [after writing to a network
file] would not necessarily return a correct list of allocated
regions. To ensure coherency [...] flush the data to the file"
fsx (generic/363) reproduces the resulting corruption against Windows
Server 2022: a range is written, an uncached read returns the data, yet
the next FSCTL_QUERY_ALLOCATED_RANGES on that range reports it as a whole
hole, so the emulation overwrites live data with zeroes. A network trace
confirmed the WRITE, the READ returning data and the query returning an
empty range list within microseconds. Samba does not exhibit this; its
query is coherent with the written data.
Write back the dirty pages, drain any outstanding I/O and issue an SMB2
FLUSH to force the server to commit the data before querying the
allocated ranges, so the query reflects the data actually present.
With this, generic/363 passes against both Windows Server 2022 and Samba
over 100000 fsx operations.
Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).
| Vendor | Product | Default status | Versions | ||||||||||||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Linux | Linux | unaffected |
|
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| Linux | Linux | affected |
|
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Advisories
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Fixes
Solution
No solution given by the vendor.
Workaround
No workaround given by the vendor.
References
History
Sun, 18 Oct 2026 19:15:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Weaknesses | CWE-750 |
Sun, 18 Oct 2026 16:00:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Description | In the Linux kernel, the following vulnerability has been resolved: smb: client: flush and commit data before querying allocated ranges The mode 0 / FALLOC_FL_KEEP_SIZE fallocate emulation for small interior ranges in smb3_simple_fallocate_range() issues FSCTL_QUERY_ALLOCATED_RANGES and zero-fills any sub-range the server reports as an unallocated hole, to force block allocation without changing file contents. This is unsafe against Windows servers. Per the Win32 documentation, FSCTL_QUERY_ALLOCATED_RANGES only reports ranges that *may* contain nonzero data and is explicitly not coherent with recently written data: "a call to FSCTL_QUERY_ALLOCATED_RANGES [after writing to a network file] would not necessarily return a correct list of allocated regions. To ensure coherency [...] flush the data to the file" fsx (generic/363) reproduces the resulting corruption against Windows Server 2022: a range is written, an uncached read returns the data, yet the next FSCTL_QUERY_ALLOCATED_RANGES on that range reports it as a whole hole, so the emulation overwrites live data with zeroes. A network trace confirmed the WRITE, the READ returning data and the query returning an empty range list within microseconds. Samba does not exhibit this; its query is coherent with the written data. Write back the dirty pages, drain any outstanding I/O and issue an SMB2 FLUSH to force the server to commit the data before querying the allocated ranges, so the query reflects the data actually present. With this, generic/363 passes against both Windows Server 2022 and Samba over 100000 fsx operations. | |
| Title | smb: client: flush and commit data before querying allocated ranges | |
| First Time appeared |
Linux
Linux linux Kernel |
|
| CPEs | cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* | |
| Vendors & Products |
Linux
Linux linux Kernel |
|
| References |
|
Projects
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MITRE
Status: PUBLISHED
Assigner: Linux
Published:
Updated: 2026-10-18T15:45:52.828Z
Reserved: 2026-09-25T10:25:14.364Z
Link: CVE-2026-98684
Vulnrichment
No data.
NVD
Status : Received
Published: 2026-10-18T16:17:21.770
Modified: 2026-10-18T16:17:21.770
Link: CVE-2026-98684
Redhat
No data.
OpenCVE Enrichment
Updated: 2026-10-18T19:00:11Z
Weaknesses
No weakness.