{"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 = <N> 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 = <N> 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..."}