CVE-2026-64567 (GCVE-0-2026-64567)

Vulnerability from cvelistv5 – Published: 2026-08-05 08:08 – Updated: 2026-08-05 08:08
VLAI
Title
btrfs: reject free space cache with more entries than pages
Summary
In the Linux kernel, the following vulnerability has been resolved: btrfs: reject free space cache with more entries than pages When loading a v1 free space cache, __load_free_space_cache() takes num_entries and num_bitmaps straight from the on-disk btrfs_free_space_header. That header is stored in the tree_root under a key with type 0, which the tree-checker has no case for, so neither count is validated before the load trusts it. The load loops num_entries times and maps the next page whenever the current one runs out, going through io_ctl_check_crc() -> io_ctl_map_page(), which does io_ctl->pages[io_ctl->index++]. But pages[] is allocated in io_ctl_init() from the cache inode's i_size, not from num_entries: num_pages = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE); io_ctl->pages = kcalloc(num_pages, sizeof(struct page *), GFP_NOFS); So if num_entries claims more records than the pages can hold, io_ctl->index runs off the end of pages[]. The write side never hits this because io_ctl_add_entry() and io_ctl_add_bitmap() both stop once io_ctl->index >= io_ctl->num_pages; the read side just never had the same check. To trigger it, take a clean cache (num_entries = <N> here), set num_entries in the header to 0x10000, and fix up the leaf checksum so it still passes the tree-checker. The cache inode has i_size = 65536, so num_pages is 16 and pages[] is a 16-pointer (kmalloc-128) array. The load now tries to read 65536 entries, io_ctl->index walks up to 16, and pages[16] is read past the array: BUG: KASAN: slab-out-of-bounds in io_ctl_check_crc (fs/btrfs/free-space-cache.c:420 fs/btrfs/free-space-cache.c:565) Read of size 8 at addr ffff88800c833a80 by task kworker/u8:3/58 io_ctl_check_crc (fs/btrfs/free-space-cache.c:420 fs/btrfs/free-space-cache.c:565) __load_free_space_cache (fs/btrfs/free-space-cache.c:655 fs/btrfs/free-space-cache.c:820) load_free_space_cache (fs/btrfs/free-space-cache.c:1017) caching_thread (fs/btrfs/block-group.c:880) btrfs_work_helper (fs/btrfs/async-thread.c:312) process_one_work worker_thread kthread ret_from_fork free-space-cache.c:420 is io_ctl_map_page(), inlined into io_ctl_check_crc() at line 565, which is why that is the frame KASAN names. The out-of-bounds slot is then treated as a struct page and handed to crc32c(), so the bad read turns into a GP fault. Add the missing check to io_ctl_check_crc(), which is where both the entry loop and the bitmap loop end up. When num_entries is too large the load now fails like any corrupt cache: __load_free_space_cache() drops it and rebuilds the free space from the extent tree, so a valid cache is never rejected.
Severity
No CVSS data available.
Assigner
References
Impacted products
Vendor Product Version
Linux Linux Affected: 5b0e95bf607ddd59b39f52d3d55e6581c817b530 , < 33878ba25e2638bc0c61623d7a05c9ca2b74c039 (git)
Affected: 5b0e95bf607ddd59b39f52d3d55e6581c817b530 , < 404a0b986e0b6e79738fdf1f0ebbbc43b9acd2a2 (git)
Affected: 5b0e95bf607ddd59b39f52d3d55e6581c817b530 , < 5e1b2ca6b34939e70fb0785e8222b53cf060016f (git)
Affected: 5b0e95bf607ddd59b39f52d3d55e6581c817b530 , < f9fef131fa3f59b857217f522fa5ea430d1b707c (git)
Affected: 5b0e95bf607ddd59b39f52d3d55e6581c817b530 , < a2d8d5647ed854e38f941741aea45b9eb15a6350 (git)
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Linux Linux Affected: 3.2
Unaffected: 0 , < 3.2 (semver)
Unaffected: 6.6.148 , ≤ 6.6.* (semver)
Unaffected: 6.12.101 , ≤ 6.12.* (semver)
Unaffected: 6.18.42 , ≤ 6.18.* (semver)
Unaffected: 7.1.6 , ≤ 7.1.* (semver)
Unaffected: 7.2-rc4 , ≤ * (original_commit_for_fix)
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{
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        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nbtrfs: reject free space cache with more entries than pages\n\nWhen loading a v1 free space cache, __load_free_space_cache() takes\nnum_entries and num_bitmaps straight from the on-disk\nbtrfs_free_space_header. That header is stored in the tree_root under a key\nwith type 0, which the tree-checker has no case for, so neither count is\nvalidated before the load trusts it.\n\nThe load loops num_entries times and maps the next page whenever the current\none runs out, going through io_ctl_check_crc() -\u003e io_ctl_map_page(), which\ndoes io_ctl-\u003epages[io_ctl-\u003eindex++]. But pages[] is allocated in\nio_ctl_init() from the cache inode\u0027s i_size, not from num_entries:\n\n\tnum_pages = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE);\n\tio_ctl-\u003epages = kcalloc(num_pages, sizeof(struct page *), GFP_NOFS);\n\nSo if num_entries claims more records than the pages can hold, io_ctl-\u003eindex\nruns off the end of pages[]. The write side never hits this because\nio_ctl_add_entry() and io_ctl_add_bitmap() both stop once\nio_ctl-\u003eindex \u003e= io_ctl-\u003enum_pages; the read side just never had the same\ncheck.\n\nTo trigger it, take a clean cache (num_entries = \u003cN\u003e here), set num_entries\nin the header to 0x10000, and fix up the leaf checksum so it still passes\nthe tree-checker. The cache inode has i_size = 65536, so num_pages is 16 and\npages[] is a 16-pointer (kmalloc-128) array. The load now tries to read\n65536 entries, io_ctl-\u003eindex walks up to 16, and pages[16] is read past the\narray:\n\n  BUG: KASAN: slab-out-of-bounds in io_ctl_check_crc (fs/btrfs/free-space-cache.c:420 fs/btrfs/free-space-cache.c:565)\n  Read of size 8 at addr ffff88800c833a80 by task kworker/u8:3/58\n   io_ctl_check_crc (fs/btrfs/free-space-cache.c:420 fs/btrfs/free-space-cache.c:565)\n   __load_free_space_cache (fs/btrfs/free-space-cache.c:655 fs/btrfs/free-space-cache.c:820)\n   load_free_space_cache (fs/btrfs/free-space-cache.c:1017)\n   caching_thread (fs/btrfs/block-group.c:880)\n   btrfs_work_helper (fs/btrfs/async-thread.c:312)\n   process_one_work\n   worker_thread\n   kthread\n   ret_from_fork\n\nfree-space-cache.c:420 is io_ctl_map_page(), inlined into io_ctl_check_crc()\nat line 565, which is why that is the frame KASAN names. The out-of-bounds\nslot is then treated as a struct page and handed to crc32c(), so the bad\nread turns into a GP fault.\n\nAdd the missing check to io_ctl_check_crc(), which is where both the entry\nloop and the bitmap loop end up. When num_entries is too large the load now\nfails like any corrupt cache: __load_free_space_cache() drops it and rebuilds\nthe free space from the extent tree, so a valid cache is never rejected."
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        "dateUpdated": "2026-08-05T08:08:06.015Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
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    "assignerShortName": "Linux",
    "cveId": "CVE-2026-64567",
    "datePublished": "2026-08-05T08:08:06.015Z",
    "dateReserved": "2026-07-19T15:36:31.797Z",
    "dateUpdated": "2026-08-05T08:08:06.015Z",
    "state": "PUBLISHED"
  },
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      "date": "2026-08-07",
      "epss": "0.00156",
      "percentile": "0.05258"
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But pages[] is allocated in\\nio_ctl_init() from the cache inode\u0027s i_size, not from num_entries:\\n\\n\\tnum_pages = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE);\\n\\tio_ctl-\u003epages = kcalloc(num_pages, sizeof(struct page *), GFP_NOFS);\\n\\nSo if num_entries claims more records than the pages can hold, io_ctl-\u003eindex\\nruns off the end of pages[]. The write side never hits this because\\nio_ctl_add_entry() and io_ctl_add_bitmap() both stop once\\nio_ctl-\u003eindex \u003e= io_ctl-\u003enum_pages; the read side just never had the same\\ncheck.\\n\\nTo trigger it, take a clean cache (num_entries = \u003cN\u003e here), set num_entries\\nin the header to 0x10000, and fix up the leaf checksum so it still passes\\nthe tree-checker. The cache inode has i_size = 65536, so num_pages is 16 and\\npages[] is a 16-pointer (kmalloc-128) array. The load now tries to read\\n65536 entries, io_ctl-\u003eindex walks up to 16, and pages[16] is read past the\\narray:\\n\\n  BUG: KASAN: slab-out-of-bounds in io_ctl_check_crc (fs/btrfs/free-space-cache.c:420 fs/btrfs/free-space-cache.c:565)\\n  Read of size 8 at addr ffff88800c833a80 by task kworker/u8:3/58\\n   io_ctl_check_crc (fs/btrfs/free-space-cache.c:420 fs/btrfs/free-space-cache.c:565)\\n   __load_free_space_cache (fs/btrfs/free-space-cache.c:655 fs/btrfs/free-space-cache.c:820)\\n   load_free_space_cache (fs/btrfs/free-space-cache.c:1017)\\n   caching_thread (fs/btrfs/block-group.c:880)\\n   btrfs_work_helper (fs/btrfs/async-thread.c:312)\\n   process_one_work\\n   worker_thread\\n   kthread\\n   ret_from_fork\\n\\nfree-space-cache.c:420 is io_ctl_map_page(), inlined into io_ctl_check_crc()\\nat line 565, which is why that is the frame KASAN names. The out-of-bounds\\nslot is then treated as a struct page and handed to crc32c(), so the bad\\nread turns into a GP fault.\\n\\nAdd the missing check to io_ctl_check_crc(), which is where both the entry\\nloop and the bitmap loop end up. When num_entries is too large the load now\\nfails like any corrupt cache: __load_free_space_cache() drops it and rebuilds\\nthe free space from the extent tree, so a valid cache is never rejected.\"}],\"affected\":[{\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"affectedData\":[{\"vendor\":\"Linux\",\"product\":\"Linux\",\"defaultStatus\":\"unaffected\",\"programFiles\":[\"fs/btrfs/free-space-cache.c\"],\"repo\":\"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\"versions\":[{\"version\":\"5b0e95bf607ddd59b39f52d3d55e6581c817b530\",\"lessThan\":\"33878ba25e2638bc0c61623d7a05c9ca2b74c039\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"5b0e95bf607ddd59b39f52d3d55e6581c817b530\",\"lessThan\":\"404a0b986e0b6e79738fdf1f0ebbbc43b9acd2a2\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"5b0e95bf607ddd59b39f52d3d55e6581c817b530\",\"lessThan\":\"5e1b2ca6b34939e70fb0785e8222b53cf060016f\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"5b0e95bf607ddd59b39f52d3d55e6581c817b530\",\"lessThan\":\"f9fef131fa3f59b857217f522fa5ea430d1b707c\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"5b0e95bf607ddd59b39f52d3d55e6581c817b530\",\"lessThan\":\"a2d8d5647ed854e38f941741aea45b9eb15a6350\",\"versionType\":\"git\",\"status\":\"affected\"}]},{\"vendor\":\"Linux\",\"product\":\"Linux\",\"defaultStatus\":\"affected\",\"programFiles\":[\"fs/btrfs/free-space-cache.c\"],\"repo\":\"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\"versions\":[{\"version\":\"3.2\",\"status\":\"affected\"},{\"version\":\"0\",\"lessThan\":\"3.2\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"6.6.148\",\"lessThanOrEqual\":\"6.6.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"6.12.101\",\"lessThanOrEqual\":\"6.12.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"6.18.42\",\"lessThanOrEqual\":\"6.18.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"7.1.6\",\"lessThanOrEqual\":\"7.1.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"7.2-rc4\",\"lessThanOrEqual\":\"*\",\"versionType\":\"original_commit_for_fix\",\"status\":\"unaffected\"}]}]}],\"metrics\":{},\"references\":[{\"url\":\"https://git.kernel.org/stable/c/33878ba25e2638bc0c61623d7a05c9ca2b74c039\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/404a0b986e0b6e79738fdf1f0ebbbc43b9acd2a2\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/5e1b2ca6b34939e70fb0785e8222b53cf060016f\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/a2d8d5647ed854e38f941741aea45b9eb15a6350\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/f9fef131fa3f59b857217f522fa5ea430d1b707c\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"}]}}",
    "redhat_vex": {
      "aggregate_severity": "Moderate",
      "current_release_date": "2026-08-06T10:23:52+00:00",
      "cve": "CVE-2026-64567",
      "id": "CVE-2026-64567",
      "initial_release_date": "2026-08-05T00:00:00+00:00",
      "product_status:known_affected": "118",
      "product_status:known_not_affected": "156",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: btrfs: reject free space cache with more entries than pages",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-64567.json",
      "version": "3"
    },
    "suse_vex": {
      "aggregate_severity": "moderate",
      "current_release_date": "2026-08-06T23:56:34Z",
      "cve": "CVE-2026-64567",
      "id": "CVE-2026-64567",
      "initial_release_date": "2026-08-06T01:06:32Z",
      "product_status:known_affected": "296",
      "source": "SUSE CSAF VEX",
      "status": "interim",
      "title": "SUSE CVE CVE-2026-64567",
      "url": "https://ftp.suse.com/pub/projects/security/csaf-vex/cve-2026-64567.json",
      "version": "3"
    }
  }
}



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  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
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