{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-89493","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","state":"PUBLISHED","assignerShortName":"Linux","dateReserved":"2026-09-11T19:38:34.714Z","datePublished":"2026-09-11T19:43:44.803Z","dateUpdated":"2026-09-14T12:00:27.844Z"},"containers":{"cna":{"providerMetadata":{"orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux","dateUpdated":"2026-09-14T12:00:27.844Z"},"descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nocfs2: validate rl_used against rl_count in refcount block validator\n\nocfs2_find_refcount_rec_in_rl() walks the on-disk refcount record array\nwith:\n\n\tfor (; i < le16_to_cpu(rb->rf_records.rl_used); i++) {\n\t\trec = &rb->rf_records.rl_recs[i];\n\t\t...\n\nrl_recs[] lives in a single metadata block (4096 bytes on the common\nconfiguration), so its real capacity is fixed by\nocfs2_refcount_recs_per_rb(sb) (247 records for a 4K block with the\n16-byte ocfs2_refcount_rec).  rl_used and rl_count are both read directly\noff disk by ocfs2_validate_refcount_block() and are never checked against\nthat capacity, nor against each other, before any refcount/reflink/CoW\noperation walks the array.\n\nA crafted (or corrupted) refcount block with rl_used == 0xffff makes the\nloop above walk far past the end of the block, dereferencing rl_recs[i]\nfor i up to 65534.  The resulting index is then handed to the sibling\nocfs2_insert_refcount_rec(), whose insert-shift does:\n\n\tif (index < le16_to_cpu(rf_list->rl_used))\n\t\tmemmove(&rf_list->rl_recs[index + 1],\n\t\t\t&rf_list->rl_recs[index],\n\t\t\t(le16_to_cpu(rf_list->rl_used) - index) *\n\t\t\t sizeof(struct ocfs2_refcount_rec));\n\ni.e.  a memmove() of up to (0xffff - index) * 16 bytes (~1 MiB) from an\noffset already past the block.  This is reachable from an ordinary reflink\n(FICLONE) against a crafted/corrupted ocfs2 image: attaching an extent\nwhose cpos sorts past every real record in the leaf forces the lookup to\nrun off the end instead of returning early on a match.  The attacker model\nis local: CAP_SYS_ADMIN mounting a crafted or corrupted ocfs2 image, or a\nraw write to the block device backing an already-mounted ocfs2 filesystem.\n\nocfs2_validate_refcount_block() already validates the block's ECC,\nsignature, rf_blkno and rf_fs_generation, but never rl_count/rl_used\nagainst the block's actual on-disk capacity.  This is the same class of\ngap that ocfs2_validate_extent_block() (fs/ocfs2/alloc.c) already closes\nfor the sibling extent-list header, which checks both the record capacity\nand the \"used\" bound before any code walks h_list.l_recs[]:\n\n\tif (le16_to_cpu(eb->h_list.l_count) != ocfs2_extent_recs_per_eb(sb)) {\n\t\trc = ocfs2_error(...);\n\t\tgoto bail;\n\t}\n\n\tif (le16_to_cpu(eb->h_list.l_next_free_rec) >\n\t    le16_to_cpu(eb->h_list.l_count)) {\n\t\trc = ocfs2_error(...);\n\t\tgoto bail;\n\t}\n\nAdd the equivalent pair of checks to ocfs2_validate_refcount_block():\nreject a refcount block whose rl_count does not match the fixed per-block\ncapacity returned by ocfs2_refcount_recs_per_rb(), and reject rl_used >\nrl_count.  Both checks are skipped when OCFS2_REFCOUNT_TREE_FL is set,\nbecause in that case the same union bytes hold an ocfs2_extent_list\n(rf_list), not the refcount record list (rf_records) -- that layout is\nalready validated separately by ocfs2_validate_extent_block() when the\nreferenced extent block is read.  This mirrors the existing\n\"!(rb->rf_flags & OCFS2_REFCOUNT_TREE_FL)\" guard used elsewhere in this\nfile (e.g.  ocfs2_get_refcount_rec()) to decide whether rf_records or\nrf_list is the live member of the union.\n\nWith this in place, a forged rl_used/rl_count is caught at block\nvalidation time (ocfs2_error()), consistent with every other corruption\ncheck in this function, instead of driving an out-of-bounds read in\nocfs2_find_refcount_rec_in_rl() and a subsequent out-of-bounds memmove()\nin ocfs2_insert_refcount_rec().\n\nVerified against a crafted image on a v6.19 KASAN (KASAN_GENERIC) build:\nreplaying the same reflink (FICLONE) reliably hit a KASAN report in\n__ocfs2_increase_refcount()/ocfs2_insert_refcount_rec() before this patch,\nand triggers no report once ocfs2_validate_refcount_block() rejects the\nforged rl_used/rl_count."}],"metrics":[{"cvssV3_1":{"version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","baseScore":8.8,"baseSeverity":"HIGH"},"scenarios":[{"lang":"en","value":"AV:N - OCFS2 registers export_operations and is commonly NFS-exported or ksmbd-shared on cluster storage; remote NFSv4.2 CLONE or ksmbd FSCTL_DUPLICATE_EXTENTS reaches vfs_clone_file_range→ocfs2_remap_file_range, and NFS WRITE/truncate on refcounted files reaches ocfs2_get_refcount_rec() and the OOB walk/memmove.\nAC:L - A crafted refcount block with rl_used=0xffff plus FICLONE/clone or write/CoW whose cpos sorts past the real leaf records deterministically drives the OOB loop and memmove; the fix commit reproduced this under KASAN with no race or uncontrollable layout.\nPR:L - Triggering needs only write/clone permission on a file whose inode points at the forged refcount block (unprivileged local user or authenticated NFS/SMB client); ocfs2_remap_file_range and ocfs2_reflink_ioctl have no capability check, and planting on-disk metadata does not require init-namespace root.\nUI:N - Once the malformed refcount block is on an already-mounted or NFS/SMB-exported OCFS2 volume, the attacker issues clone, write, or truncate themselves; no separate victim mount, click, or administrator action is required at exploit time.\nS:U - The out-of-bounds read and write corrupt kernel memory in the host parsing the OCFS2 refcount block; impact stays within that kernel's security authority and does not cross a VM, container, or IOMMU boundary.\nC:H - ocfs2_find_refcount_rec_in_rl() indexes rl_recs[i] for i up to 65534 past a single 4K metadata block, performing an approximately 1 MiB out-of-bounds read of adjacent kernel memory and enabling high-bandwidth disclosure.\nI:H - ocfs2_insert_refcount_rec() memmove()s up to (0xffff-index)*16 bytes (~1 MiB) from and to offsets already past the block and writes rl_recs[index] out of bounds, which is an arbitrary kernel out-of-bounds write exploitable for control-flow hijacking.\nA:H - The same OOB access was reproduced as a KASAN fault in __ocfs2_increase_refcount()/ocfs2_insert_refcount_rec() and causes a kernel oops or panic, fully denying availability on the affected node."}]}],"affected":[{"product":"Linux","vendor":"Linux","defaultStatus":"unaffected","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/ocfs2/refcounttree.c"],"versions":[{"version":"f2c870e3b12e38da6d9b5b17c4c8ae56a0ed68e4","lessThan":"f882e9e32d017a6569b2996c63ba3864717788e6","status":"affected","versionType":"git"},{"version":"f2c870e3b12e38da6d9b5b17c4c8ae56a0ed68e4","lessThan":"5593b63028cb43a6cda75a65ce1db95f00ea6857","status":"affected","versionType":"git"},{"version":"f2c870e3b12e38da6d9b5b17c4c8ae56a0ed68e4","lessThan":"c8b02f4ee91e757b3fff556c7168b24b7ae55132","status":"affected","versionType":"git"},{"version":"f2c870e3b12e38da6d9b5b17c4c8ae56a0ed68e4","lessThan":"97584e93fc49a2d59252ac60467e9279f11b1b5b","status":"affected","versionType":"git"},{"version":"f2c870e3b12e38da6d9b5b17c4c8ae56a0ed68e4","lessThan":"af56e90cb546cb0c47bef059335365283f61d6a4","status":"affected","versionType":"git"},{"version":"f2c870e3b12e38da6d9b5b17c4c8ae56a0ed68e4","lessThan":"0761d2c9494424469a0d30a9da3496ca010b0b2d","status":"affected","versionType":"git"},{"version":"f2c870e3b12e38da6d9b5b17c4c8ae56a0ed68e4","lessThan":"04ead708e13ddcb9c39319cbe02a18cef99cb823","status":"affected","versionType":"git"},{"version":"f2c870e3b12e38da6d9b5b17c4c8ae56a0ed68e4","lessThan":"4ca62df6bc0708947b48da3f6a712ecb8e73929c","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/ocfs2/refcounttree.c"],"versions":[{"version":"2.6.32","status":"affected"},{"version":"0","lessThan":"2.6.32","status":"unaffected","versionType":"semver"},{"version":"5.10.270","lessThanOrEqual":"5.10.*","status":"unaffected","versionType":"semver"},{"version":"5.15.221","lessThanOrEqual":"5.15.*","status":"unaffected","versionType":"semver"},{"version":"6.1.188","lessThanOrEqual":"6.1.*","status":"unaffected","versionType":"semver"},{"version":"6.6.157","lessThanOrEqual":"6.6.*","status":"unaffected","versionType":"semver"},{"version":"6.12.109","lessThanOrEqual":"6.12.*","status":"unaffected","versionType":"semver"},{"version":"6.18.50","lessThanOrEqual":"6.18.*","status":"unaffected","versionType":"semver"},{"version":"7.2.4","lessThanOrEqual":"7.2.*","status":"unaffected","versionType":"semver"},{"version":"7.3-rc1","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":"2.6.32","versionEndExcluding":"5.10.270"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.32","versionEndExcluding":"5.15.221"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.32","versionEndExcluding":"6.1.188"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.32","versionEndExcluding":"6.6.157"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.32","versionEndExcluding":"6.12.109"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.32","versionEndExcluding":"6.18.50"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.32","versionEndExcluding":"7.2.4"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.32","versionEndExcluding":"7.3-rc1"}]}]}],"references":[{"url":"https://git.kernel.org/stable/c/f882e9e32d017a6569b2996c63ba3864717788e6"},{"url":"https://git.kernel.org/stable/c/5593b63028cb43a6cda75a65ce1db95f00ea6857"},{"url":"https://git.kernel.org/stable/c/c8b02f4ee91e757b3fff556c7168b24b7ae55132"},{"url":"https://git.kernel.org/stable/c/97584e93fc49a2d59252ac60467e9279f11b1b5b"},{"url":"https://git.kernel.org/stable/c/af56e90cb546cb0c47bef059335365283f61d6a4"},{"url":"https://git.kernel.org/stable/c/0761d2c9494424469a0d30a9da3496ca010b0b2d"},{"url":"https://git.kernel.org/stable/c/04ead708e13ddcb9c39319cbe02a18cef99cb823"},{"url":"https://git.kernel.org/stable/c/4ca62df6bc0708947b48da3f6a712ecb8e73929c"}],"title":"ocfs2: validate rl_used against rl_count in refcount block validator","x_generator":{"engine":"bippy-1.2.0"}}}}