{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-64567","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","state":"PUBLISHED","assignerShortName":"Linux","dateReserved":"2026-07-19T15:36:31.797Z","datePublished":"2026-08-05T08:08:06.015Z","dateUpdated":"2026-08-19T16:28:41.793Z"},"containers":{"cna":{"providerMetadata":{"orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux","dateUpdated":"2026-08-19T16:28:41.793Z"},"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."}],"metrics":[{"cvssV3_1":{"version":"3.1","vectorString":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","baseScore":7.8,"baseSeverity":"HIGH"},"scenarios":[{"lang":"en","value":"AV:L - The bug is reached only by mounting a crafted btrfs image so caching_thread → load_free_space_cache → __load_free_space_cache runs; there is no network or adjacent protocol path into v1 free-space cache loading.\nAC:L - The attacker authors a v1 cache with inflated num_entries (and a matching leaf checksum); cache_generation auto-enables SPACE_CACHE on mount, and the OOB in io_ctl_check_crc/io_ctl_map_page is deterministic with no race or uncontrolled condition.\nPR:L - btrfs lacks FS_USERNS_MOUNT, but an unprivileged local user can loop-setup and mount a crafted image via udisks2/polkit on typical desktops/kiosks; real init-namespace root is not required.\nUI:N - In the loop/udisks mount scenario the attacker mounts the image themselves; no separate victim must open a file, click through a prompt, or otherwise interact.\nS:U - The slab OOB and resulting kernel memory misuse stay inside the host kernel's authority; no VM escape, IOMMU bypass, or sandbox boundary is crossed.\nC:H - An out-of-bounds pages[] read yields a forged struct page pointer that is passed to page_address/crc32c and then used as the source for further cache parsing, giving an arbitrary kernel-memory read primitive once adjacent slab contents are groomed.\nI:H - The forged page pointer continues into entry/bitmap load paths (including copy_page into kernel bitmaps and linking attacker-controlled free-space records), a memory-corruption primitive exploitable for arbitrary write and control-flow hijack.\nA:H - Without a valid page pointer the OOB dereference reliably faults (KASAN slab-OOB then GP fault on crc32c as in the report), crashing or oopsing the kernel."}]}],"affected":[{"product":"Linux","vendor":"Linux","defaultStatus":"unaffected","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/btrfs/free-space-cache.c"],"versions":[{"version":"5b0e95bf607ddd59b39f52d3d55e6581c817b530","lessThan":"8ded74c654a982dc8581a17b0caa7fcedb20de69","status":"affected","versionType":"git"},{"version":"5b0e95bf607ddd59b39f52d3d55e6581c817b530","lessThan":"c9c38066b6446e83668c041702bb639b0ca49363","status":"affected","versionType":"git"},{"version":"5b0e95bf607ddd59b39f52d3d55e6581c817b530","lessThan":"094734c7aaa2b36751dc32480a680a4952685e78","status":"affected","versionType":"git"},{"version":"5b0e95bf607ddd59b39f52d3d55e6581c817b530","lessThan":"33878ba25e2638bc0c61623d7a05c9ca2b74c039","status":"affected","versionType":"git"},{"version":"5b0e95bf607ddd59b39f52d3d55e6581c817b530","lessThan":"404a0b986e0b6e79738fdf1f0ebbbc43b9acd2a2","status":"affected","versionType":"git"},{"version":"5b0e95bf607ddd59b39f52d3d55e6581c817b530","lessThan":"5e1b2ca6b34939e70fb0785e8222b53cf060016f","status":"affected","versionType":"git"},{"version":"5b0e95bf607ddd59b39f52d3d55e6581c817b530","lessThan":"f9fef131fa3f59b857217f522fa5ea430d1b707c","status":"affected","versionType":"git"},{"version":"5b0e95bf607ddd59b39f52d3d55e6581c817b530","lessThan":"a2d8d5647ed854e38f941741aea45b9eb15a6350","status":"affected","versionType":"git"}]},{"product":"Linux","vendor":"Linux","defaultStatus":"affected","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/btrfs/free-space-cache.c"],"versions":[{"version":"3.2","status":"affected"},{"version":"0","lessThan":"3.2","status":"unaffected","versionType":"semver"},{"version":"5.10.265","lessThanOrEqual":"5.10.*","status":"unaffected","versionType":"semver"},{"version":"5.15.216","lessThanOrEqual":"5.15.*","status":"unaffected","versionType":"semver"},{"version":"6.1.183","lessThanOrEqual":"6.1.*","status":"unaffected","versionType":"semver"},{"version":"6.6.148","lessThanOrEqual":"6.6.*","status":"unaffected","versionType":"semver"},{"version":"6.12.101","lessThanOrEqual":"6.12.*","status":"unaffected","versionType":"semver"},{"version":"6.18.42","lessThanOrEqual":"6.18.*","status":"unaffected","versionType":"semver"},{"version":"7.1.6","lessThanOrEqual":"7.1.*","status":"unaffected","versionType":"semver"},{"version":"7.2","lessThanOrEqual":"*","status":"unaffected","versionType":"original_commit_for_fix"}]}],"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"3.2","versionEndExcluding":"5.10.265"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"3.2","versionEndExcluding":"5.15.216"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"3.2","versionEndExcluding":"6.1.183"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"3.2","versionEndExcluding":"6.6.148"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"3.2","versionEndExcluding":"6.12.101"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"3.2","versionEndExcluding":"6.18.42"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"3.2","versionEndExcluding":"7.1.6"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"3.2","versionEndExcluding":"7.2"}]}]}],"references":[{"url":"https://git.kernel.org/stable/c/8ded74c654a982dc8581a17b0caa7fcedb20de69"},{"url":"https://git.kernel.org/stable/c/c9c38066b6446e83668c041702bb639b0ca49363"},{"url":"https://git.kernel.org/stable/c/094734c7aaa2b36751dc32480a680a4952685e78"},{"url":"https://git.kernel.org/stable/c/33878ba25e2638bc0c61623d7a05c9ca2b74c039"},{"url":"https://git.kernel.org/stable/c/404a0b986e0b6e79738fdf1f0ebbbc43b9acd2a2"},{"url":"https://git.kernel.org/stable/c/5e1b2ca6b34939e70fb0785e8222b53cf060016f"},{"url":"https://git.kernel.org/stable/c/f9fef131fa3f59b857217f522fa5ea430d1b707c"},{"url":"https://git.kernel.org/stable/c/a2d8d5647ed854e38f941741aea45b9eb15a6350"}],"title":"btrfs: reject free space cache with more entries than pages","x_generator":{"engine":"bippy-1.2.0"}}}}