In the Linux kernel, the following vulnerability has been resolved:
ext4: fix off-by-one errors in fast-commit block filling
Due to several different off-by-one errors, or perhaps due to a late
change in design that wasn't fully reflected in the code that was
actually merged, there are several very strange constraints on how
fast-commit blocks are filled with tlv entries:
- tlvs must start at least 10 bytes before the end of the block, even
though the minimum tlv length is 8. Otherwise, the replay code will
ignore them. (BUG: ext4_fc_reserve_space() could violate this
requirement if called with a len of blocksize - 9 or blocksize - 8.
Fortunately, this doesn't seem to happen currently.)
- tlvs must end at least 1 byte before the end of the block. Otherwise
the replay code will consider them to be invalid. This quirk
contributed to a bug (fixed by an earlier commit) where uninitialized
memory was being leaked to disk in the last byte of blocks.
Also, strangely these constraints don't apply to the replay code in
e2fsprogs, which will accept any tlvs in the blocks (with no bounds
checks at all, but that is a separate issue...).
Given that this all seems to be a bug, let's fix it by just filling
blocks with tlv entries in the natural way.
Note that old kernels will be unable to replay fast-commit journals
created by kernels that have this commit.
ext4: fix off-by-one errors in fast-commit block filling
Due to several different off-by-one errors, or perhaps due to a late
change in design that wasn't fully reflected in the code that was
actually merged, there are several very strange constraints on how
fast-commit blocks are filled with tlv entries:
- tlvs must start at least 10 bytes before the end of the block, even
though the minimum tlv length is 8. Otherwise, the replay code will
ignore them. (BUG: ext4_fc_reserve_space() could violate this
requirement if called with a len of blocksize - 9 or blocksize - 8.
Fortunately, this doesn't seem to happen currently.)
- tlvs must end at least 1 byte before the end of the block. Otherwise
the replay code will consider them to be invalid. This quirk
contributed to a bug (fixed by an earlier commit) where uninitialized
memory was being leaked to disk in the last byte of blocks.
Also, strangely these constraints don't apply to the replay code in
e2fsprogs, which will accept any tlvs in the blocks (with no bounds
checks at all, but that is a separate issue...).
Given that this all seems to be a bug, let's fix it by just filling
blocks with tlv entries in the natural way.
Note that old kernels will be unable to replay fast-commit journals
created by kernels that have this commit.
Metrics
Affected Vendors & Products
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Fixes
Solution
No solution given by the vendor.
Workaround
No workaround given by the vendor.
References
History
Thu, 02 Oct 2025 00:15:00 +0000
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| Metrics |
threat_severity
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cvssV3_1
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Wed, 01 Oct 2025 12:00:00 +0000
| Type | Values Removed | Values Added |
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| Description | In the Linux kernel, the following vulnerability has been resolved: ext4: fix off-by-one errors in fast-commit block filling Due to several different off-by-one errors, or perhaps due to a late change in design that wasn't fully reflected in the code that was actually merged, there are several very strange constraints on how fast-commit blocks are filled with tlv entries: - tlvs must start at least 10 bytes before the end of the block, even though the minimum tlv length is 8. Otherwise, the replay code will ignore them. (BUG: ext4_fc_reserve_space() could violate this requirement if called with a len of blocksize - 9 or blocksize - 8. Fortunately, this doesn't seem to happen currently.) - tlvs must end at least 1 byte before the end of the block. Otherwise the replay code will consider them to be invalid. This quirk contributed to a bug (fixed by an earlier commit) where uninitialized memory was being leaked to disk in the last byte of blocks. Also, strangely these constraints don't apply to the replay code in e2fsprogs, which will accept any tlvs in the blocks (with no bounds checks at all, but that is a separate issue...). Given that this all seems to be a bug, let's fix it by just filling blocks with tlv entries in the natural way. Note that old kernels will be unable to replay fast-commit journals created by kernels that have this commit. | |
| Title | ext4: fix off-by-one errors in fast-commit block filling | |
| References |
|
MITRE
Status: PUBLISHED
Assigner: Linux
Published:
Updated: 2025-10-01T11:42:07.245Z
Reserved: 2025-09-17T14:53:07.008Z
Link: CVE-2022-50428
Vulnrichment
No data.
NVD
Status : Received
Published: 2025-10-01T12:15:34.403
Modified: 2025-10-01T12:15:34.403
Link: CVE-2022-50428
Redhat
OpenCVE Enrichment
No data.