{ "cvss": 7.8, "datePublished": "2026-08-05T08:16:36.277", "dateUpdated": "2026-11-03T18:15:39.353", "description": "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() -> io_ctl_map_page(), which\ndoes io_ctl->pages[io_ctl->index++]. But pages[] is allocated in\nio_ctl_init() from the cache inode's i_size, not from num_entries:\n\n\tnum_pages = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE);\n\tio_ctl->pages = kcalloc(num_pages, sizeof(struct page *), GFP_NOFS);\n\nSo if num_entries claims more records than the pages can hold, io_ctl->index\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->index >= io_ctl->num_pages; the read side just never had the same\ncheck.\n\nTo trigger it, take a clean cache (num_entries = 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->index 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.", "id": "CVE-2026-64567", "raw": { "affected": [ { "affectedData": [ { "defaultStatus": "unaffected", "product": "Linux", "programFiles": [ "fs/btrfs/free-space-cache.c" ], "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "vendor": "Linux", "versions": [ { "lessThan": "8ded74c654a982dc8581a17b0caa7fcedb20de69", "status": "affected", "version": "5b0e95bf607ddd59b39f52d3d55e6581c817b530", "versionType": "git" }, { "lessThan": "c9c38066b6446e83668c041702bb639b0ca49363", "status": "affected", "version": "5b0e95bf607ddd59b39f52d3d55e6581c817b530", "versionType": "git" }, { "lessThan": "094734c7aaa2b36751dc32480a680a4952685e78", "status": "affected", "version": "5b0e95bf607ddd59b39f52d3d55e6581c817b530", "versionType": "git" }, { "lessThan": "33878ba25e2638bc0c61623d7a05c9ca2b74c039", "status": "affected", "version": "5b0e95bf607ddd59b39f52d3d55e6581c817b530", "versionType": "git" }, { "lessThan": "404a0b986e0b6e79738fdf1f0ebbbc43b9acd2a2", "status": "affected", "version": "5b0e95bf607ddd59b39f52d3d55e6581c817b530", "versionType": "git" }, { "lessThan": "5e1b2ca6b34939e70fb0785e8222b53cf060016f", "status": "affected", "version": "5b0e95bf607ddd59b39f52d3d55e6581c817b530", "versionType": "git" }, { "lessThan": "f9fef131fa3f59b857217f522fa5ea430d1b707c", "status": "affected", "version": "5b0e95bf607ddd59b39f52d3d55e6581c817b530", "versionType": "git" }, { "lessThan": "a2d8d5647ed854e38f941741aea45b9eb15a6350", "status": "affected", "version": "5b0e95bf607ddd59b39f52d3d55e6581c817b530", "versionType": "git" } ] }, { "defaultStatus": "affected", "product": "Linux", "programFiles": [ "fs/btrfs/free-space-cache.c" ], "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "vendor": "Linux", "versions": [ { "status": "affected", "version": "3.2" }, { "lessThan": "3.2", "status": "unaffected", "version": "0", "versionType": "semver" }, { "lessThanOrEqual": "5.10.*", "status": "unaffected", "version": "5.10.265", "versionType": "semver" }, { "lessThanOrEqual": "5.15.*", "status": "unaffected", "version": "5.15.216", "versionType": "semver" }, { "lessThanOrEqual": "6.1.*", "status": "unaffected", "version": "6.1.183", "versionType": "semver" }, { "lessThanOrEqual": "6.6.*", "status": "unaffected", "version": "6.6.148", "versionType": "semver" }, { "lessThanOrEqual": "6.12.*", "status": "unaffected", "version": "6.12.101", "versionType": "semver" }, { "lessThanOrEqual": "6.18.*", "status": "unaffected", "version": "6.18.42", "versionType": "semver" }, { "lessThanOrEqual": "7.1.*", "status": "unaffected", "version": "7.1.6", "versionType": "semver" }, { "lessThanOrEqual": "*", "status": "unaffected", "version": "7.2", "versionType": "original_commit_for_fix" } ] } ], "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67" } ], "cveTags": [], "descriptions": [ { "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() -> io_ctl_map_page(), which\ndoes io_ctl->pages[io_ctl->index++]. But pages[] is allocated in\nio_ctl_init() from the cache inode's i_size, not from num_entries:\n\n\tnum_pages = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE);\n\tio_ctl->pages = kcalloc(num_pages, sizeof(struct page *), GFP_NOFS);\n\nSo if num_entries claims more records than the pages can hold, io_ctl->index\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->index >= io_ctl->num_pages; the read side just never had the same\ncheck.\n\nTo trigger it, take a clean cache (num_entries = 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->index 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." } ], "id": "CVE-2026-64567", "lastModified": "2026-11-03T18:15:39.353", "metrics": { "cvssMetricV31": [ { "cvssData": { "attackComplexity": "LOW", "attackVector": "LOCAL", "availabilityImpact": "HIGH", "baseScore": 7.8, "baseSeverity": "HIGH", "confidentialityImpact": "HIGH", "integrityImpact": "HIGH", "privilegesRequired": "LOW", "scope": "UNCHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H", "version": "3.1" }, "exploitabilityScore": 1.8, "impactScore": 5.9, "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "type": "Secondary" } ], "ssvcV203": [ { "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "ssvcData": { "id": "CVE-2026-64567", "options": [ { "exploitation": "none" }, { "automatable": "no" }, { "technicalImpact": "total" } ], "role": "CISA Coordinator", "timestamp": "2026-10-16T15:42:59.944567Z", "version": "2.0.3" } } ] }, "published": "2026-08-05T08:16:36.277", "references": [ { "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/094734c7aaa2b36751dc32480a680a4952685e78" }, { "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "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/8ded74c654a982dc8581a17b0caa7fcedb20de69" }, { "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/c9c38066b6446e83668c041702bb639b0ca49363" }, { "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/f9fef131fa3f59b857217f522fa5ea430d1b707c" } ], "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "vulnStatus": "Awaiting Analysis", "weaknesses": [ { "description": [ { "lang": "en", "value": "CWE-125" } ], "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "type": "Secondary" } ] }, "severity": "HIGH", "source": "nvd", "title": "In the Linux kernel, the following vulnerability has been resolved:\n\nbtrfs: reject free space cache with more entries..." }