ghsa-96wx-hqjc-pv4q
Vulnerability from github
In the Linux kernel, the following vulnerability has been resolved:
btrfs: fix qgroup reserve overflow the qgroup limit
We use extent_changeset->bytes_changed in qgroup_reserve_data() to record how many bytes we set for EXTENT_QGROUP_RESERVED state. Currently the bytes_changed is set as "unsigned int", and it will overflow if we try to fallocate a range larger than 4GiB. The result is we reserve less bytes and eventually break the qgroup limit.
Unlike regular buffered/direct write, which we use one changeset for each ordered extent, which can never be larger than 256M. For fallocate, we use one changeset for the whole range, thus it no longer respects the 256M per extent limit, and caused the problem.
The following example test script reproduces the problem:
$ cat qgroup-overflow.sh #!/bin/bash
DEV=/dev/sdj MNT=/mnt/sdj
mkfs.btrfs -f $DEV mount $DEV $MNT
# Set qgroup limit to 2GiB. btrfs quota enable $MNT btrfs qgroup limit 2G $MNT
# Try to fallocate a 3GiB file. This should fail. echo echo "Try to fallocate a 3GiB file..." fallocate -l 3G $MNT/3G.file
# Try to fallocate a 5GiB file. echo echo "Try to fallocate a 5GiB file..." fallocate -l 5G $MNT/5G.file
# See we break the qgroup limit. echo sync btrfs qgroup show -r $MNT
umount $MNT
When running the test:
$ ./qgroup-overflow.sh (...)
Try to fallocate a 3GiB file... fallocate: fallocate failed: Disk quota exceeded
Try to fallocate a 5GiB file...
qgroupid rfer excl max_rfer -------- ---- ---- -------- 0/5 5.00GiB 5.00GiB 2.00GiB
Since we have no control of how bytes_changed is used, it's better to set it to u64.
{
"affected": [],
"aliases": [
"CVE-2022-49075"
],
"database_specific": {
"cwe_ids": [
"CWE-190"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2025-02-26T07:00:44Z",
"severity": "MODERATE"
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\nbtrfs: fix qgroup reserve overflow the qgroup limit\n\nWe use extent_changeset-\u003ebytes_changed in qgroup_reserve_data() to record\nhow many bytes we set for EXTENT_QGROUP_RESERVED state. Currently the\nbytes_changed is set as \"unsigned int\", and it will overflow if we try to\nfallocate a range larger than 4GiB. The result is we reserve less bytes\nand eventually break the qgroup limit.\n\nUnlike regular buffered/direct write, which we use one changeset for\neach ordered extent, which can never be larger than 256M. For\nfallocate, we use one changeset for the whole range, thus it no longer\nrespects the 256M per extent limit, and caused the problem.\n\nThe following example test script reproduces the problem:\n\n $ cat qgroup-overflow.sh\n #!/bin/bash\n\n DEV=/dev/sdj\n MNT=/mnt/sdj\n\n mkfs.btrfs -f $DEV\n mount $DEV $MNT\n\n # Set qgroup limit to 2GiB.\n btrfs quota enable $MNT\n btrfs qgroup limit 2G $MNT\n\n # Try to fallocate a 3GiB file. This should fail.\n echo\n echo \"Try to fallocate a 3GiB file...\"\n fallocate -l 3G $MNT/3G.file\n\n # Try to fallocate a 5GiB file.\n echo\n echo \"Try to fallocate a 5GiB file...\"\n fallocate -l 5G $MNT/5G.file\n\n # See we break the qgroup limit.\n echo\n sync\n btrfs qgroup show -r $MNT\n\n umount $MNT\n\nWhen running the test:\n\n $ ./qgroup-overflow.sh\n (...)\n\n Try to fallocate a 3GiB file...\n fallocate: fallocate failed: Disk quota exceeded\n\n Try to fallocate a 5GiB file...\n\n qgroupid\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 rfer\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 excl\u00a0\u00a0\u00a0\u00a0 max_rfer\n --------\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 ----\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 ----\u00a0\u00a0\u00a0\u00a0 --------\n 0/5\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 5.00GiB\u00a0\u00a0\u00a0\u00a0\u00a0 5.00GiB\u00a0\u00a0\u00a0\u00a0\u00a0 2.00GiB\n\nSince we have no control of how bytes_changed is used, it\u0027s better to\nset it to u64.",
"id": "GHSA-96wx-hqjc-pv4q",
"modified": "2025-09-23T21:30:54Z",
"published": "2025-09-23T21:30:54Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2022-49075"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/0355387ea5b02d353c9415613fab908fac5c52a6"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/44277c50fdba5019ca25bfad1b71e2561b0de11b"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/4b98799e181b4326a613108cf37acc1f55d21b45"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/6bfff81286d4491f02dad7814bae5c77c9ad2320"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/7941b74ed49b6db25efbef2256ebef843c11a010"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/82ae73ac963cee877ce34f7c31b2b456b516e96c"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/b642b52d0b50f4d398cb4293f64992d0eed2e2ce"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/f3d97b22a708bf9e3f3ac2ba232bcefd0b0c136b"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H",
"type": "CVSS_V3"
}
]
}
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