In the Linux kernel, the following vulnerability has been resolved:
smb/client: invalidate fscache for fallocate range operations
smb3_zero_range(), smb3_punch_hole(), smb3_insert_range(), and
smb3_collapse_range() modify file contents through server-side range
operations. These operations discard the affected page cache, but leave
the FS-Cache cookie valid, so a later read may return data cached before
the range operation.
Fix this by invalidating FS-Cache after outstanding I/O has completed
and before modifying the file on the server.
Run the following as root on a CIFS mount with fsc enabled and an active
CacheFiles backend:
bash -c '
MNT=/mnt/cifs
FILE="$MNT/repro"
# Generate four 1 MiB random blocks: [A][B][C][D].
dd if=/dev/urandom of=/tmp/src bs=1M count=4 status=none
# Expected contents after zeroing B: [A][zero][C][D].
cp /tmp/src /tmp/expected
dd if=/dev/zero of=/tmp/expected bs=1M seek=1 count=1 \
conv=notrunc status=none
cp /tmp/src "$FILE"
# Populate FS-Cache, then discard the page cache.
sync
echo 1 > /proc/sys/vm/drop_caches
cat "$FILE" > /dev/null
sync
echo 1 > /proc/sys/vm/drop_caches
fallocate --zero-range -o 1M -l 1M "$FILE"
if cmp -s /tmp/expected "$FILE"; then
echo "readback: OK"
else
echo "readback: STALE DATA"
fi
'
Before this change, the readback differs from /tmp/expected:
readback: STALE DATA
After this change, it matches:
readback: OK
smb/client: invalidate fscache for fallocate range operations
smb3_zero_range(), smb3_punch_hole(), smb3_insert_range(), and
smb3_collapse_range() modify file contents through server-side range
operations. These operations discard the affected page cache, but leave
the FS-Cache cookie valid, so a later read may return data cached before
the range operation.
Fix this by invalidating FS-Cache after outstanding I/O has completed
and before modifying the file on the server.
Run the following as root on a CIFS mount with fsc enabled and an active
CacheFiles backend:
bash -c '
MNT=/mnt/cifs
FILE="$MNT/repro"
# Generate four 1 MiB random blocks: [A][B][C][D].
dd if=/dev/urandom of=/tmp/src bs=1M count=4 status=none
# Expected contents after zeroing B: [A][zero][C][D].
cp /tmp/src /tmp/expected
dd if=/dev/zero of=/tmp/expected bs=1M seek=1 count=1 \
conv=notrunc status=none
cp /tmp/src "$FILE"
# Populate FS-Cache, then discard the page cache.
sync
echo 1 > /proc/sys/vm/drop_caches
cat "$FILE" > /dev/null
sync
echo 1 > /proc/sys/vm/drop_caches
fallocate --zero-range -o 1M -l 1M "$FILE"
if cmp -s /tmp/expected "$FILE"; then
echo "readback: OK"
else
echo "readback: STALE DATA"
fi
'
Before this change, the readback differs from /tmp/expected:
readback: STALE DATA
After this change, it matches:
readback: OK
Metrics
Affected Vendors & Products
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| Vendors | Products |
|---|---|
|
Linux
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Linux Kernel
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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
Fri, 25 Sep 2026 12:45:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Weaknesses | CWE-203 |
Fri, 25 Sep 2026 10:45:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Description | In the Linux kernel, the following vulnerability has been resolved: smb/client: invalidate fscache for fallocate range operations smb3_zero_range(), smb3_punch_hole(), smb3_insert_range(), and smb3_collapse_range() modify file contents through server-side range operations. These operations discard the affected page cache, but leave the FS-Cache cookie valid, so a later read may return data cached before the range operation. Fix this by invalidating FS-Cache after outstanding I/O has completed and before modifying the file on the server. Run the following as root on a CIFS mount with fsc enabled and an active CacheFiles backend: bash -c ' MNT=/mnt/cifs FILE="$MNT/repro" # Generate four 1 MiB random blocks: [A][B][C][D]. dd if=/dev/urandom of=/tmp/src bs=1M count=4 status=none # Expected contents after zeroing B: [A][zero][C][D]. cp /tmp/src /tmp/expected dd if=/dev/zero of=/tmp/expected bs=1M seek=1 count=1 \ conv=notrunc status=none cp /tmp/src "$FILE" # Populate FS-Cache, then discard the page cache. sync echo 1 > /proc/sys/vm/drop_caches cat "$FILE" > /dev/null sync echo 1 > /proc/sys/vm/drop_caches fallocate --zero-range -o 1M -l 1M "$FILE" if cmp -s /tmp/expected "$FILE"; then echo "readback: OK" else echo "readback: STALE DATA" fi ' Before this change, the readback differs from /tmp/expected: readback: STALE DATA After this change, it matches: readback: OK | |
| Title | smb/client: invalidate fscache for fallocate range operations | |
| 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: 2026-09-25T10:36:06.581Z
Reserved: 2026-09-25T10:25:14.318Z
Link: CVE-2026-98124
Vulnrichment
No data.
NVD
Status : Received
Published: 2026-09-25T11:17:43.720
Modified: 2026-09-25T11:17:43.720
Link: CVE-2026-98124
Redhat
No data.
OpenCVE Enrichment
Updated: 2026-09-25T12:45:16Z
Weaknesses